vendor/NetBSD/tests/2026.02.14_2vendor/NetBSD/tests

83 files changed, 9485 insertions, 0 deletions

diff --git a/kernel/arch/aarch64/contextspfunc.S b/kernel/arch/aarch64/contextspfunc.S
new file mode 100644
index 000000000000..9a4e3059a8e0
--- /dev/null
+++ b/kernel/arch/aarch64/contextspfunc.S
@@ -0,0 +1,46 @@
+/*	$NetBSD: contextspfunc.S,v 1.2 2025/06/08 18:55:35 christos Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: contextspfunc.S,v 1.2 2025/06/08 18:55:35 christos Exp $")
+
+/*
+ * contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+ENTRY(contextspfunc)
+	mov	x0, sp
+	adrp	x1, _C_LABEL(contextsp)
+	str	x0, [x1, :lo12:_C_LABEL(contextsp)]
+	b	_C_LABEL(contextdone)
+END(contextspfunc)
diff --git a/kernel/arch/aarch64/execregs.c b/kernel/arch/aarch64/execregs.c
new file mode 100644
index 000000000000..4c7697fe98c7
--- /dev/null
+++ b/kernel/arch/aarch64/execregs.c
@@ -0,0 +1,226 @@
+/*	$NetBSD: execregs.c,v 1.1 2025/02/27 00:55:31 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: execregs.c,v 1.1 2025/02/27 00:55:31 riastradh Exp $");
+
+#include "execregs.h"
+
+#include <errno.h>
+#include <spawn.h>
+#include <stddef.h>
+#include <unistd.h>
+
+extern char **environ;
+
+static unsigned long
+nonnull(unsigned long x)
+{
+
+	x |= x << 8;
+	x |= x << 16;
+	x |= x << 32;
+	return x;
+}
+
+int
+execregschild(char *path)
+{
+	/* x0: used to pass exec arg0, nonnull anyway (path) */
+	/* x1: used to pass exec arg1, nonnull anyway (argv) */
+	/* x2: used to pass exec arg2, nonnull anyway (environ) */
+	register long x3 __asm("x3") = nonnull(3);
+	register long x4 __asm("x4") = nonnull(4);
+	register long x5 __asm("x5") = nonnull(5);
+	register long x6 __asm("x6") = nonnull(6);
+	register long x7 __asm("x7") = nonnull(7);
+	register long x8 __asm("x8") = nonnull(8);
+	register long x9 __asm("x9") = nonnull(9);
+	register long x10 __asm("x10") = nonnull(10);
+	register long x11 __asm("x11") = nonnull(11);
+	register long x12 __asm("x12") = nonnull(12);
+	register long x13 __asm("x13") = nonnull(13);
+	register long x14 __asm("x14") = nonnull(14);
+	register long x15 __asm("x15") = nonnull(15);
+	register long x16 __asm("x16") = nonnull(16);
+	register long x17 __asm("x17") = nonnull(17);
+	register long x18 __asm("x18") = nonnull(18);
+	register long x19 __asm("x19") = nonnull(19);
+	register long x20 __asm("x20") = nonnull(20);
+	register long x21 __asm("x21") = nonnull(21);
+	register long x22 __asm("x22") = nonnull(22);
+	register long x23 __asm("x23") = nonnull(23);
+	register long x24 __asm("x24") = nonnull(24);
+	register long x25 __asm("x25") = nonnull(25);
+	register long x26 __asm("x26") = nonnull(26);
+	register long x27 __asm("x27") = nonnull(27);
+	register long x28 __asm("x28") = nonnull(28);
+	/* x29: frame pointer, nonnull anyway */
+	/* x30: link register, nonnull anyway */
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("" :
+	    "+r"(x3),
+	    "+r"(x4),
+	    "+r"(x5),
+	    "+r"(x6),
+	    "+r"(x7),
+	    "+r"(x8),
+	    "+r"(x9),
+	    "+r"(x10),
+	    "+r"(x11),
+	    "+r"(x12),
+	    "+r"(x13),
+	    "+r"(x14),
+	    "+r"(x15),
+	    "+r"(x16),
+	    "+r"(x17)
+	    :: "memory");
+	/* pacify gcc error: more than 30 operands in 'asm' */
+	__asm volatile("" :
+	    "+r"(x18),
+	    "+r"(x19),
+	    "+r"(x20),
+	    "+r"(x21),
+	    "+r"(x22),
+	    "+r"(x23),
+	    "+r"(x24),
+	    "+r"(x25),
+	    "+r"(x26),
+	    "+r"(x27),
+	    "+r"(x28)
+	    :: "memory");
+
+	return execve(path, argv, envp);
+}
+
+pid_t
+spawnregschild(char *path, int fd)
+{
+	/* x0: used to pass posix_spawn arg0, nonnull anyway (&pid) */
+	/* x1: used to pass posix_spawn arg1, nonnull anyway (path) */
+	/* x2: used to pass posix_spawn arg2, nonnull anyway (&fileacts) */
+	/* x3: used to pass posix_spawn arg3, nonnull anyway (&attr) */
+	/* x4: used to pass posix_spawn arg3, nonnull anyway (argv) */
+	/* x5: used to pass posix_spawn arg3, nonnull anyway (environ) */
+	register long x6 __asm("x6") = nonnull(6);
+	register long x7 __asm("x7") = nonnull(7);
+	register long x8 __asm("x8") = nonnull(8);
+	register long x9 __asm("x9") = nonnull(9);
+	register long x10 __asm("x10") = nonnull(10);
+	register long x11 __asm("x11") = nonnull(11);
+	register long x12 __asm("x12") = nonnull(12);
+	register long x13 __asm("x13") = nonnull(13);
+	register long x14 __asm("x14") = nonnull(14);
+	register long x15 __asm("x15") = nonnull(15);
+	register long x16 __asm("x16") = nonnull(16);
+	register long x17 __asm("x17") = nonnull(17);
+	register long x18 __asm("x18") = nonnull(18);
+	register long x19 __asm("x19") = nonnull(19);
+	register long x20 __asm("x20") = nonnull(20);
+	register long x21 __asm("x21") = nonnull(21);
+	register long x22 __asm("x22") = nonnull(22);
+	register long x23 __asm("x23") = nonnull(23);
+	register long x24 __asm("x24") = nonnull(24);
+	register long x25 __asm("x25") = nonnull(25);
+	register long x26 __asm("x26") = nonnull(26);
+	register long x27 __asm("x27") = nonnull(27);
+	register long x28 __asm("x28") = nonnull(28);
+	/* x29: frame pointer, nonnull anyway */
+	/* x30: link register, nonnull anyway */
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+	posix_spawn_file_actions_t fileacts;
+	posix_spawnattr_t attr;
+	pid_t pid;
+	int error;
+
+	error = posix_spawn_file_actions_init(&fileacts);
+	if (error)
+		goto out;
+	error = posix_spawn_file_actions_adddup2(&fileacts, fd, STDOUT_FILENO);
+	if (error)
+		goto out;
+	error = posix_spawnattr_init(&attr);
+	if (error)
+		goto out;
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("" :
+	    "+r"(x6),
+	    "+r"(x7),
+	    "+r"(x8),
+	    "+r"(x9),
+	    "+r"(x10),
+	    "+r"(x11),
+	    "+r"(x12),
+	    "+r"(x13),
+	    "+r"(x14),
+	    "+r"(x15),
+	    "+r"(x16),
+	    "+r"(x17),
+	    "+r"(x18),
+	    "+r"(x19),
+	    "+r"(x20)
+	    :: "memory");
+	/* pacify gcc error: more than 30 operands in 'asm' */
+	__asm volatile("" :
+	    "+r"(x21),
+	    "+r"(x22),
+	    "+r"(x23),
+	    "+r"(x24),
+	    "+r"(x25),
+	    "+r"(x26),
+	    "+r"(x27),
+	    "+r"(x28)
+	    :: "memory");
+
+	error = posix_spawn(&pid, path, &fileacts, &attr, argv, envp);
+	if (error)
+		goto out;
+
+out:	posix_spawnattr_destroy(&attr);
+	posix_spawn_file_actions_destroy(&fileacts);
+	if (error) {
+		errno = error;
+		return -1;
+	}
+	return 0;
+}
diff --git a/kernel/arch/aarch64/execregs.h b/kernel/arch/aarch64/execregs.h
new file mode 100644
index 000000000000..471a3859c4d1
--- /dev/null
+++ b/kernel/arch/aarch64/execregs.h
@@ -0,0 +1,86 @@
+/*	$NetBSD: execregs.h,v 1.1 2025/02/27 00:55:31 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_AARCH64_EXECREGS_H
+#define	TESTS_KERNEL_ARCH_AARCH64_EXECREGS_H
+
+#include <sys/cdefs.h>
+
+#define	NEXECREGS	31
+
+#ifndef _LOCORE
+
+#include <unistd.h>
+
+/*
+ * Ordered by struct reg in sys/arch/aarch64/include/reg.h for
+ * convenience of auditing.  Must match h_execregs.S.
+ */
+static const char *const regname[] = {
+	"x0",
+	"x1",
+	/* x2: ps_strings */
+	"x3",
+	"x4",
+	"x5",
+	"x6",
+	"x7",
+	"x8",
+	"x9",
+	"x10",
+	"x11",
+	"x12",
+	"x13",
+	"x14",
+	"x15",
+	"x16",
+	"x17",
+	"x18",
+	"x19",
+	"x20",
+	"x21",
+	"x22",
+	"x23",
+	"x24",
+	"x25",
+	"x26",
+	"x27",
+	"x28",
+	"x29",
+	"x30",
+	"tpidr",
+};
+
+__CTASSERT(NEXECREGS == __arraycount(regname));
+
+int	execregschild(char *);
+pid_t	spawnregschild(char *, int);
+
+#endif	/* _LOCORE */
+
+#endif	/* TESTS_KERNEL_ARCH_AARCH64_EXECREGS_H */
diff --git a/kernel/arch/aarch64/execsp.S b/kernel/arch/aarch64/execsp.S
new file mode 100644
index 000000000000..52c1472afef6
--- /dev/null
+++ b/kernel/arch/aarch64/execsp.S
@@ -0,0 +1,99 @@
+/*	$NetBSD: execsp.S,v 1.3 2025/06/04 19:25:45 christos Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: execsp.S,v 1.3 2025/06/04 19:25:45 christos Exp $")
+
+/*
+ * void execsp_start(void (*cleanup@x0)(void), void *obj_main@x1,
+ *     struct ps_strings *ps_strings@x2)
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ */
+ENTRY(execsp_start)
+	mov	x16, sp
+	adrp	x17, _C_LABEL(startsp)
+	str	x16, [x17, :lo12:_C_LABEL(startsp)]
+	b	_C_LABEL(__start)
+END(execsp_start)
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+ENTRY(execsp_ctor)
+	mov	x16, sp
+	adrp	x17, _C_LABEL(ctorsp)
+	str	x16, [x17, :lo12:_C_LABEL(ctorsp)]
+	ret
+END(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.section .init_array,"aw",%init_array
+	.p2align 3
+	.xword	_C_LABEL(execsp_ctor)
+
+/*
+ * int main(int argc@x0, char **argv@x1, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+ENTRY(main)
+	mov	x16, sp
+	adrp	x17, _C_LABEL(mainsp)
+	str	x16, [x17, :lo12:_C_LABEL(mainsp)]
+	mov	x0, #0
+	ret
+END(main)
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+ENTRY(execsp_dtor)
+	mov	x16, sp
+	adrp	x17, _C_LABEL(dtorsp)
+	str	x16, [x17, :lo12:_C_LABEL(dtorsp)]
+	b	_C_LABEL(execsp_main)
+END(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.section .fini_array,"aw",%fini_array
+	.p2align 3
+	.xword	_C_LABEL(execsp_dtor)
diff --git a/kernel/arch/aarch64/h_execregs.S b/kernel/arch/aarch64/h_execregs.S
new file mode 100644
index 000000000000..f060911067f4
--- /dev/null
+++ b/kernel/arch/aarch64/h_execregs.S
@@ -0,0 +1,84 @@
+/*	$NetBSD: h_execregs.S,v 1.2 2025/04/25 12:58:40 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <sys/syscall.h>
+
+#include <machine/asm.h>
+
+#include "execregs.h"
+
+ENTRY(execregs_start)
+	/* create a stack frame with NEXECREGS*8 bytes, aligned to 16-byte */
+	stp	fp, lr, [sp, #-(16 + ((NEXECREGS*8 + 15)/16)*16)]!
+
+	/* store registers to buffer on stack */
+	stp	x0, x1, [sp, #16]	/* order matches execregs.h */
+	/* x2: ps_strings */
+	stp	x3, x4, [sp, #(16 + 1*2*8)]
+	stp	x5, x6, [sp, #(16 + 2*2*8)]
+	stp	x7, x8, [sp, #(16 + 3*2*8)]
+	stp	x9, x10, [sp, #(16 + 4*2*8)]
+	stp	x11, x12, [sp, #(16 + 5*2*8)]
+	stp	x13, x14, [sp, #(16 + 6*2*8)]
+	stp	x15, x16, [sp, #(16 + 7*2*8)]
+	stp	x17, x18, [sp, #(16 + 8*2*8)]
+	stp	x19, x20, [sp, #(16 + 9*2*8)]
+	stp	x21, x22, [sp, #(16 + 10*2*8)]
+	stp	x23, x24, [sp, #(16 + 11*2*8)]
+	stp	x25, x26, [sp, #(16 + 12*2*8)]
+	stp	x27, x28, [sp, #(16 + 13*2*8)]
+	stp	x29, x30, [sp, #(16 + 14*2*8)]
+	mrs	x0, tpidr_el0
+	str	x0, [sp, #(16 + 15*2*8)]
+
+	/* call write(STDOUT_FILENO, regs, sizeof(regs)) */
+	mov	x0, #1			/* arg0 := STDOUT_FILENO */
+	add	x1, sp, #16		/* arg1 := regs */
+	mov	x2, #(NEXECREGS*8)	/* arg2 := sizeof(regs) */
+	svc	#SYS_write
+
+	b.cs	2f			/* bail if write failed */
+	cmp	x0, #(NEXECREGS*8)	/* bail if wrote wrong # of bytes */
+	b.ne	2f
+
+	/* call exit(0) */
+	mov	x0, #0			/* arg0 := 0 */
+1:	svc	#SYS_exit
+	brk	#0xffff			/* paranoia */
+
+2:	/* call exit(127) */
+	mov	x0, #127		/* arg0 := 127 */
+	b	1b
+END(execregs_start)
+
+/* main stub to simplify linking */
+ENTRY(main)
+	brk	#0xffff
+END(main)
diff --git a/kernel/arch/aarch64/signalsphandler.S b/kernel/arch/aarch64/signalsphandler.S
new file mode 100644
index 000000000000..246ed383273d
--- /dev/null
+++ b/kernel/arch/aarch64/signalsphandler.S
@@ -0,0 +1,46 @@
+/*	$NetBSD: signalsphandler.S,v 1.2 2025/06/08 18:55:35 christos Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: signalsphandler.S,v 1.2 2025/06/08 18:55:35 christos Exp $")
+
+/*
+ * signalsphandler(signo@x0)
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+ENTRY(signalsphandler)
+	mov	x0, sp
+	adrp	x1, _C_LABEL(signalsp)
+	str	x0, [x1, :lo12:_C_LABEL(signalsp)]
+	ret
+END(signalsphandler)
diff --git a/kernel/arch/aarch64/stack_pointer.h b/kernel/arch/aarch64/stack_pointer.h
new file mode 100644
index 000000000000..3bd7e6f65335
--- /dev/null
+++ b/kernel/arch/aarch64/stack_pointer.h
@@ -0,0 +1,42 @@
+/*	$NetBSD: stack_pointer.h,v 1.2 2025/04/20 22:31:00 riastradh Exp $	*/
+
+/*
+ * Copyright (c) 2024 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_AARCH64_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_AARCH64_STACK_POINTER_H
+
+#define MISALIGN_SP				\
+	__asm__ volatile (			\
+		"sub sp, sp, #8"		\
+	)
+
+#define FIX_SP					\
+	__asm__ volatile (			\
+		"add sp, sp, #8"		\
+	)
+
+#endif	/* TESTS_KERNEL_ARCH_AARCH64_STACK_POINTER_H */
diff --git a/kernel/arch/aarch64/threadspfunc.S b/kernel/arch/aarch64/threadspfunc.S
new file mode 100644
index 000000000000..90f779d5e961
--- /dev/null
+++ b/kernel/arch/aarch64/threadspfunc.S
@@ -0,0 +1,43 @@
+/*	$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $")
+
+/*
+ * void *threadspfunc(void *cookie@x0)
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+ENTRY(threadspfunc)
+	mov	x0, sp
+	ret
+END(threadspfunc)
diff --git a/kernel/arch/alpha/contextspfunc.S b/kernel/arch/alpha/contextspfunc.S
new file mode 100644
index 000000000000..da198f089124
--- /dev/null
+++ b/kernel/arch/alpha/contextspfunc.S
@@ -0,0 +1,50 @@
+/*	$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $")
+
+	.set noat
+	.text
+
+/*
+ * contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+LEAF(contextspfunc, 1)
+	LDGP(pv)
+	ldq	at_reg, contextsp(gp)	!literal
+	stq	sp, 0(at_reg)
+	ldq	pv, contextdone(gp)	!literal
+	jmp	(pv), contextdone
+END(contextspfunc)
diff --git a/kernel/arch/alpha/execsp.S b/kernel/arch/alpha/execsp.S
new file mode 100644
index 000000000000..08eaa521fa03
--- /dev/null
+++ b/kernel/arch/alpha/execsp.S
@@ -0,0 +1,106 @@
+/*	$NetBSD: execsp.S,v 1.2 2025/04/21 02:31:22 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: execsp.S,v 1.2 2025/04/21 02:31:22 riastradh Exp $")
+
+	.set noat
+	.text
+
+/*
+ * void execsp_start(void *stackpointer@a0, void (*cleanup@a1)(void),
+ *     void *obj_main@a2, struct ps_strings *ps_strings@a3)
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ */
+LEAF(execsp_start, 4)
+	LDGP(pv)
+	ldq	at_reg, startsp(gp)	!literal
+	stq	sp, 0(at_reg)
+	ldq	pv, __start(gp)		!literal
+	jmp	(pv), __start
+END(execsp_start)
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+LEAF(execsp_ctor, 0)
+	LDGP(pv)
+	ldq	at_reg, ctorsp(gp)	!literal
+	stq	sp, 0(at_reg)
+	RET
+END(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.pushsection .ctors,"aw",@progbits
+	.p2align 3
+	.quad	execsp_ctor
+	.popsection
+
+/*
+ * int main(int argc@a0, char **argv@a1, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+LEAF(main, 2)
+	LDGP(pv)
+	ldq	at_reg, mainsp(gp)	!literal
+	stq	sp, 0(at_reg)
+	mov	zero, v0
+	RET
+END(main)
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+LEAF(execsp_dtor, 0)
+	LDGP(pv)
+	ldq	at_reg, dtorsp(gp)	!literal
+	stq	sp, 0(at_reg)
+	ldq	pv, execsp_main(gp)	!literal
+	jmp	(pv), execsp_main
+END(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.pushsection .dtors,"aw",@progbits
+	.p2align 3
+	.quad	execsp_dtor
+	.popsection
diff --git a/kernel/arch/alpha/signalsphandler.S b/kernel/arch/alpha/signalsphandler.S
new file mode 100644
index 000000000000..eaa3f2cdb654
--- /dev/null
+++ b/kernel/arch/alpha/signalsphandler.S
@@ -0,0 +1,49 @@
+/*	$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:31:57 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:31:57 riastradh Exp $")
+
+	.set noat
+	.text
+
+/*
+ * signalsphandler(signo@a0)
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+LEAF(signalsphandler, 1)
+	LDGP(pv)
+	ldq	at_reg, signalsp(gp)	!literal
+	stq	sp, 0(at_reg)
+	RET
+END(signalsphandler)
diff --git a/kernel/arch/alpha/stack_pointer.h b/kernel/arch/alpha/stack_pointer.h
new file mode 100644
index 000000000000..58c581ffde0a
--- /dev/null
+++ b/kernel/arch/alpha/stack_pointer.h
@@ -0,0 +1,35 @@
+/*	$NetBSD: stack_pointer.h,v 1.1 2025/04/20 22:31:57 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_ALPHA_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_ALPHA_STACK_POINTER_H
+
+#define MISALIGN_SP	__asm __volatile("lda $sp,-1($sp)" ::: "memory")
+#define FIX_SP		__asm __volatile("lda $sp,1($sp)" ::: "memory")
+
+#endif	/* TESTS_KERNEL_ARCH_ALPHA_STACK_POINTER_H */
diff --git a/kernel/arch/alpha/threadspfunc.S b/kernel/arch/alpha/threadspfunc.S
new file mode 100644
index 000000000000..413387bb0867
--- /dev/null
+++ b/kernel/arch/alpha/threadspfunc.S
@@ -0,0 +1,46 @@
+/*	$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $")
+
+	.set noat
+	.text
+
+/*
+ * void *threadspfunc(void *cookie@a0)
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+LEAF(threadspfunc, 1)
+	mov	sp, v0
+	RET
+END(threadspfunc)
diff --git a/kernel/arch/arm/contextspfunc.S b/kernel/arch/arm/contextspfunc.S
new file mode 100644
index 000000000000..cf7fec19fb2a
--- /dev/null
+++ b/kernel/arch/arm/contextspfunc.S
@@ -0,0 +1,51 @@
+/*	$NetBSD: contextspfunc.S,v 1.2 2025/05/07 16:26:47 uwe Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: contextspfunc.S,v 1.2 2025/05/07 16:26:47 uwe Exp $")
+
+/*
+ * contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+ENTRY(contextspfunc)
+0:	GOT_INIT(r0, .Lgot)
+	mov	r1, sp
+	GOT_GET(r2, r0, .Lcontextsp)
+	str	r1, [r2]
+	b	PLT_SYM(_C_LABEL(contextdone))
+
+	GOT_INITSYM(.Lgot, 0b)
+.Lcontextsp:
+	.word	GOT_SYM(contextsp)
+END(contextspfunc)
diff --git a/kernel/arch/arm/execsp.S b/kernel/arch/arm/execsp.S
new file mode 100644
index 000000000000..b02587ef2b33
--- /dev/null
+++ b/kernel/arch/arm/execsp.S
@@ -0,0 +1,119 @@
+/*	$NetBSD: execsp.S,v 1.4 2025/05/07 16:26:47 uwe Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: execsp.S,v 1.4 2025/05/07 16:26:47 uwe Exp $")
+
+/*
+ * void execsp_start(struct ps_strings *ps_strings@r0, void *obj_main@r1,
+ *     void (*cleanup@r2)(void))
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ */
+ENTRY(execsp_start)
+0:	GOT_INIT(r3, .Lgot.execsp_start)
+	mov	r4, sp
+	GOT_GET(r5, r3, .Lstartsp)
+	str	r4, [r5]
+	b	PLT_SYM(_C_LABEL(__start))
+
+	GOT_INITSYM(.Lgot.execsp_start, 0b)
+.Lstartsp:
+	.word	GOT_SYM(startsp)
+END(execsp_start)
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+ENTRY(execsp_ctor)
+0:	GOT_INIT(r0, .Lgot.execsp_ctor)
+	mov	r1, sp
+	GOT_GET(r2, r0, .Lctorsp)
+	str	r1, [r2]
+	RET
+
+	GOT_INITSYM(.Lgot.execsp_ctor, 0b)
+.Lctorsp:
+	.word	GOT_SYM(ctorsp)
+END(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.section .init_array,"aw",%init_array
+	.p2align 2
+	.word	_C_LABEL(execsp_ctor)
+
+/*
+ * int main(int argc@r0, char **argv@r1, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+ENTRY(main)
+0:	GOT_INIT(r0, .Lgot.main)
+	mov	r1, sp
+	GOT_GET(r2, r0, .Lmainsp)
+	str	r1, [r2]
+	mov	r0, #0
+	RET
+
+	GOT_INITSYM(.Lgot.main, 0b)
+.Lmainsp:
+	.word	GOT_SYM(mainsp)
+END(main)
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+ENTRY(execsp_dtor)
+0:	GOT_INIT(r0, .Lgot.execsp_dtor)
+	mov	r1, sp
+	GOT_GET(r2, r0, .Ldtorsp)
+	str	r1, [r2]
+	b	PLT_SYM(_C_LABEL(execsp_main))
+
+	GOT_INITSYM(.Lgot.execsp_dtor, 0b)
+.Ldtorsp:
+	.word	GOT_SYM(dtorsp)
+END(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.section .fini_array,"aw",%fini_array
+	.p2align 2
+	.word	_C_LABEL(execsp_dtor)
diff --git a/kernel/arch/arm/signalsphandler.S b/kernel/arch/arm/signalsphandler.S
new file mode 100644
index 000000000000..21b7d26a53b9
--- /dev/null
+++ b/kernel/arch/arm/signalsphandler.S
@@ -0,0 +1,51 @@
+/*	$NetBSD: signalsphandler.S,v 1.3 2025/05/07 16:26:47 uwe Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: signalsphandler.S,v 1.3 2025/05/07 16:26:47 uwe Exp $")
+
+/*
+ * signalsphandler(signo@r0)
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+ENTRY(signalsphandler)
+0:	GOT_INIT(r0, .Lgot)
+	mov	r1, sp
+	GOT_GET(r2, r0, .Lsignalsp)
+	str	r1, [r2]
+	RET
+
+	GOT_INITSYM(.Lgot, 0b)
+.Lsignalsp:
+	.word	GOT_SYM(signalsp)
+END(signalsphandler)
diff --git a/kernel/arch/arm/stack_pointer.h b/kernel/arch/arm/stack_pointer.h
new file mode 100644
index 000000000000..73d10c341138
--- /dev/null
+++ b/kernel/arch/arm/stack_pointer.h
@@ -0,0 +1,35 @@
+/*	$NetBSD: stack_pointer.h,v 1.1 2025/04/25 02:24:01 riastradh Exp $	*/
+
+/*
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_ARM_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_ARM_STACK_POINTER_H
+
+#define MISALIGN_SP	__asm __volatile("sub sp, sp, #1")
+#define FIX_SP		__asm __volatile("add sp, sp, #1")
+
+#endif	/* TESTS_KERNEL_ARCH_ARM_STACK_POINTER_H */
diff --git a/kernel/arch/arm/threadspfunc.S b/kernel/arch/arm/threadspfunc.S
new file mode 100644
index 000000000000..5f34c547cadf
--- /dev/null
+++ b/kernel/arch/arm/threadspfunc.S
@@ -0,0 +1,43 @@
+/*	$NetBSD: threadspfunc.S,v 1.1 2025/04/25 02:24:01 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: threadspfunc.S,v 1.1 2025/04/25 02:24:01 riastradh Exp $")
+
+/*
+ * void *threadspfunc(void *cookie@r0)
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+ENTRY(threadspfunc)
+	mov	r0, sp
+	RET
+END(threadspfunc)
diff --git a/kernel/arch/hppa/contextspfunc.S b/kernel/arch/hppa/contextspfunc.S
new file mode 100644
index 000000000000..683f59808c95
--- /dev/null
+++ b/kernel/arch/hppa/contextspfunc.S
@@ -0,0 +1,48 @@
+/*	$NetBSD: contextspfunc.S,v 1.2 2025/04/21 12:06:08 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: contextspfunc.S,v 1.2 2025/04/21 12:06:08 riastradh Exp $")
+
+/*
+ * contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+LEAF_ENTRY(contextspfunc)
+	addil	LT%_C_LABEL(contextdone), %r19	/* r20 := contextdone */
+	ldw	RT%_C_LABEL(contextdone)(%r1), %r20
+	addil	LT%_C_LABEL(contextsp), %r19	/* r21 := &contextsp */
+	ldw	RT%_C_LABEL(contextsp)(%r1), %r21
+	bv	%r0(%r20)			/* jump to contextdone */
+	 stw	%sp, 0(%r21)			/* contextsp := sp */
+EXIT(contextspfunc)
diff --git a/kernel/arch/hppa/execregs.c b/kernel/arch/hppa/execregs.c
new file mode 100644
index 000000000000..c064d3a36e37
--- /dev/null
+++ b/kernel/arch/hppa/execregs.c
@@ -0,0 +1,387 @@
+/*	$NetBSD: execregs.c,v 1.2 2025/02/28 16:08:19 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: execregs.c,v 1.2 2025/02/28 16:08:19 riastradh Exp $");
+
+#include "execregs.h"
+
+#include <errno.h>
+#include <spawn.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <unistd.h>
+
+extern char **environ;
+
+static unsigned long
+nonnull(unsigned long x)
+{
+
+	x |= x << 8;
+	x |= x << 16;
+	return x;
+}
+
+/*
+ * setfpregs()
+ *
+ *	Set up all the floating-point registers with something nonzero
+ *	in each one.  We initialize the floating-point status register
+ *	to set various bits so it's not all zero, but nothing that
+ *	would trigger traps.
+ */
+static void
+setfpregs(void)
+{
+	static const uint64_t fpe[] = {
+		(__BITS(63,59)		/* all exception flags (VZOUI) set */
+		    | __BIT(58)		/* C bit (comparison) set */
+		    | __BITS(54,43)	/* CQ (comparison queue) all set */
+		    | __SHIFTIN(1, __BITS(42,41))	/* round toward zero */
+		    | __SHIFTIN(0, __BIT(38))	/* no delayed trap */
+		    | __SHIFTIN(1, __BIT(37))	/* Denormalized As Zero */
+		    | __SHIFTIN(0, __BITS(36,32))	/* exceptions masked */
+		    | 0x10101010),
+		0x9191919111111111,
+		0x9292929212121212,
+		0x9393939313131313,
+	};
+	const uint64_t *fpep = fpe;
+
+	static const double fr[28] = {
+		0x1.04p0, 0x1.05p0, 0x1.06p0, 0x1.07p0,
+		0x1.08p0, 0x1.09p0, 0x1.0ap0, 0x1.0bp0,
+		0x1.0cp0, 0x1.0dp0, 0x1.0ep0, 0x1.0fp0,
+		0x1.10p0, 0x1.11p0, 0x1.12p0, 0x1.13p0,
+		0x1.14p0, 0x1.15p0, 0x1.16p0, 0x1.17p0,
+		0x1.18p0, 0x1.19p0, 0x1.1ap0, 0x1.1bp0,
+		0x1.1cp0, 0x1.1dp0, 0x1.1ep0, 0x1.1fp0,
+	};
+	const double *frp = fr;
+
+	__asm volatile(
+		"fldds,ma	8(%0), %%fr0\n\t"
+		"fldds,ma	8(%0), %%fr1\n\t"
+		"fldds,ma	8(%0), %%fr2\n\t"
+		"fldds		0(%0), %%fr3"
+	    : "+r"(fpep)
+	    : "m"(fpe));
+
+	__asm volatile(
+		"fldds,ma	8(%0), %%fr4\n\t"
+		"fldds,ma	8(%0), %%fr5\n\t"
+		"fldds,ma	8(%0), %%fr6\n\t"
+		"fldds,ma	8(%0), %%fr7\n\t"
+		"fldds,ma	8(%0), %%fr8\n\t"
+		"fldds,ma	8(%0), %%fr9\n\t"
+		"fldds,ma	8(%0), %%fr10\n\t"
+		"fldds,ma	8(%0), %%fr11\n\t"
+		"fldds,ma	8(%0), %%fr12\n\t"
+		"fldds,ma	8(%0), %%fr13\n\t"
+		"fldds,ma	8(%0), %%fr14\n\t"
+		"fldds,ma	8(%0), %%fr15\n\t"
+		"fldds,ma	8(%0), %%fr16\n\t"
+		"fldds,ma	8(%0), %%fr17\n\t"
+		"fldds,ma	8(%0), %%fr18\n\t"
+		"fldds,ma	8(%0), %%fr19\n\t"
+		"fldds,ma	8(%0), %%fr20\n\t"
+		"fldds,ma	8(%0), %%fr21\n\t"
+		"fldds,ma	8(%0), %%fr22\n\t"
+		"fldds,ma	8(%0), %%fr23\n\t"
+		"fldds,ma	8(%0), %%fr24\n\t"
+		"fldds,ma	8(%0), %%fr25\n\t"
+		"fldds,ma	8(%0), %%fr26\n\t"
+		"fldds,ma	8(%0), %%fr27\n\t"
+		"fldds,ma	8(%0), %%fr28\n\t"
+		"fldds,ma	8(%0), %%fr29\n\t"
+		"fldds,ma	8(%0), %%fr30\n\t"
+		"fldds		0(%0), %%fr31"
+	    : "+r"(frp)
+	    : "m"(fr));
+}
+
+/*
+ * setpsw()
+ *
+ *	Set some bits in PSW, the processor status word.
+ */
+static void
+setpsw(void)
+{
+	uint32_t x = 0xe0000000, y = 0xffffffff, sum;
+
+	/*
+	 * Trigger some arithmetic that causes the carry/borrow
+	 * (PSW[C/B]) bits to be set.
+	 *
+	 * XXX Also set PSW[V].
+	 */
+	__asm volatile("sh3add %[sum], %[x], %[y]"
+	    : /* outputs */ [sum] "=r"(sum)
+	    : /* inputs */ [x] "r"(x), [y] "r"(y));
+}
+
+int
+execregschild(char *path)
+{
+	register long t1 __asm("r22") = nonnull(22);
+	register long t2 __asm("r21") = nonnull(21);
+	/* r30/sp: stack pointer */
+	register long t3 __asm("r20") = nonnull(20);
+	/* cr17/iisq_head: privileged */
+	/* cr17/iisq_tail: privileged */
+	/* cr18/iioq_head: privileged */
+	/* cr18/iioq_tail: privileged */
+	/* cr15/eiem: privileged */
+	/* cr22/ipsw: privileged */
+	/* sr3: privileged(?) */
+	/* cr8/pidr1: privileged */
+	/* cr20/isr: privileged */
+	/* cr21/ior: privileged */
+	/* cr19/iir: privileged */
+	/* flags: N/A(?) */
+	long sar = nonnull(0x8a);	/* cr11 */
+	/* r1: ADDIL (add immediate left) result, nonnull anyway */
+	/* r2/rp: return pointer, nonnull anyway */
+	/* r3: frame pointer, nonnull anyway */
+	register long r4 __asm("r4") = nonnull(4);
+	register long r5 __asm("r5") = nonnull(5);
+	register long r6 __asm("r6") = nonnull(6);
+	register long r7 __asm("r7") = nonnull(7);
+	register long r8 __asm("r8") = nonnull(8);
+	register long r9 __asm("r9") = nonnull(9);
+	register long r10 __asm("r10") = nonnull(10);
+	register long r11 __asm("r11") = nonnull(11);
+	register long r12 __asm("r12") = nonnull(12);
+	register long r13 __asm("r13") = nonnull(13);
+	register long r14 __asm("r14") = nonnull(14);
+	register long r15 __asm("r15") = nonnull(15);
+	register long r16 __asm("r16") = nonnull(16);
+	register long r17 __asm("r17") = nonnull(17);
+	register long r18 __asm("r18") = nonnull(18);
+	register long t4 __asm("r19") = nonnull(19);
+	register long arg3 __asm("r23") = nonnull(23);
+	/* r24/arg2: envp, nonnull anyway */
+	/* r25/arg1: argv, nonnull anyway */
+	/* r26/arg0: path, nonnull anyway */
+	/* r27/dp: data pointer, nonnull anyway */
+	register long ret0 __asm("r28") = nonnull(28);
+	register long ret1 __asm("r29") = nonnull(29);
+	register long r31 __asm("r31") = nonnull(31);
+	/* sr0-sr7: space registers initialized by kernel */
+	/* cr9/pidr2: privileged */
+	/* cr12/pidr3: privileged */
+	/* cr13/pidr4: privileged */
+	/* cr0/rctr: privileged */
+	/* cr10/ccr: privileged */
+	/* cr23/eirr: privileged */
+	/* cr24: privileged */
+	/* cr25/vtop: privileged */
+	/* cr27/tr3: _lwp_private, thread-local storage -- nonnull anyway */
+	/* cr28: privileged */
+	/* cr30/fpregs: privileged */
+	/* cr31: privileged */
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+
+	setfpregs();
+	setpsw();
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("mtctl %[sar], %%sar"	/* cr11 */
+	    : /* outputs */
+	    : [sar] "r"(sar)
+	    : "memory");
+	__asm volatile("" :
+	    "+r"(t1),
+	    "+r"(t2),
+	    "+r"(t3),
+	    "+r"(r4),
+	    "+r"(r5),
+	    "+r"(r6),
+	    "+r"(r7),
+	    "+r"(r8),
+	    "+r"(r9),
+	    "+r"(r10),
+	    "+r"(r11),
+	    "+r"(r12)
+	    :: "memory");
+	/* pacify gcc error: more than 30 operands in 'asm' */
+	__asm volatile("" :
+	    "+r"(r13),
+	    "+r"(r14),
+	    "+r"(r15),
+	    "+r"(r16),
+	    "+r"(r17),
+	    "+r"(r18),
+	    "+r"(t4),
+	    "+r"(arg3),
+	    "+r"(ret0),
+	    "+r"(ret1),
+	    "+r"(r31)
+	    :: "memory");
+
+	return execve(path, argv, envp);
+}
+
+pid_t
+spawnregschild(char *path, int fd)
+{
+	register long t1 __asm("r22") = nonnull(22);
+	register long t2 __asm("r21") = nonnull(21);
+	/* r30/sp: stack pointer */
+	register long t3 __asm("r20") = nonnull(20);
+	/* cr17/iisq_head: privileged */
+	/* cr17/iisq_tail: privileged */
+	/* cr18/iioq_head: privileged */
+	/* cr18/iioq_tail: privileged */
+	/* cr15/eiem: privileged */
+	/* cr22/ipsw: privileged */
+	/* sr3: privileged(?) */
+	/* cr8/pidr1: privileged */
+	/* cr20/isr: privileged */
+	/* cr21/ior: privileged */
+	/* cr19/iir: privileged */
+	/* flags: N/A(?) */
+	long sar = nonnull(0x8a);	/* cr11 */
+	/* r1: ADDIL (add immediate left) result, nonnull anyway */
+	/* r2/rp: return pointer, nonnull anyway */
+	/* r3: frame pointer, nonnull anyway */
+	register long r4 __asm("r4") = nonnull(4);
+	register long r5 __asm("r5") = nonnull(5);
+	register long r6 __asm("r6") = nonnull(6);
+	register long r7 __asm("r7") = nonnull(7);
+	register long r8 __asm("r8") = nonnull(8);
+	register long r9 __asm("r9") = nonnull(9);
+	register long r10 __asm("r10") = nonnull(10);
+	register long r11 __asm("r11") = nonnull(11);
+	register long r12 __asm("r12") = nonnull(12);
+	register long r13 __asm("r13") = nonnull(13);
+	register long r14 __asm("r14") = nonnull(14);
+	register long r15 __asm("r15") = nonnull(15);
+	register long r16 __asm("r16") = nonnull(16);
+	register long r17 __asm("r17") = nonnull(17);
+	register long r18 __asm("r18") = nonnull(18);
+	register long t4 __asm("r19") = nonnull(19);
+	/* r23/arg3: attrp, nonnull anyway */
+	/* r24/arg2: fileactsp, nonnull anyway */
+	/* r25/arg1: path, nonnull anyway */
+	/* r26/arg0: pidp, nonnull anyway */
+	/* r27/dp: data pointer, nonnull anyway */
+	register long ret0 __asm("r28") = nonnull(28);
+	register long ret1 __asm("r29") = nonnull(29);
+	register long r31 __asm("r31") = nonnull(31);
+	/* sr0-sr7: space registers initialized by kernel */
+	/* cr9/pidr2: privileged */
+	/* cr12/pidr3: privileged */
+	/* cr13/pidr4: privileged */
+	/* cr0/rctr: privileged */
+	/* cr10/ccr: privileged */
+	/* cr23/eirr: privileged */
+	/* cr24: privileged */
+	/* cr25/vtop: privileged */
+	/* cr27/tr3: _lwp_private, thread-local storage -- nonnull anyway */
+	/* cr28: privileged */
+	/* cr30/fpregs: privileged */
+	/* cr31: privileged */
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+	posix_spawn_file_actions_t fileacts;
+	posix_spawnattr_t attr;
+	pid_t pid;
+	int error;
+
+	error = posix_spawn_file_actions_init(&fileacts);
+	if (error)
+		goto out;
+	error = posix_spawn_file_actions_adddup2(&fileacts, fd, STDOUT_FILENO);
+	if (error)
+		goto out;
+	error = posix_spawnattr_init(&attr);
+	if (error)
+		goto out;
+
+	setfpregs();
+	setpsw();
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("mtctl %[sar], %%sar"	/* cr11 */
+	    : /* outputs */
+	    : [sar] "r"(sar)
+	    : "memory");
+	__asm volatile("" :
+	    "+r"(t1),
+	    "+r"(t2),
+	    "+r"(t3),
+	    "+r"(r4),
+	    "+r"(r5),
+	    "+r"(r6),
+	    "+r"(r7),
+	    "+r"(r8),
+	    "+r"(r9),
+	    "+r"(r10),
+	    "+r"(r11),
+	    "+r"(r12)
+	    :: "memory");
+	/* pacify gcc error: more than 30 operands in 'asm' */
+	__asm volatile("" :
+	    "+r"(r13),
+	    "+r"(r14),
+	    "+r"(r15),
+	    "+r"(r16),
+	    "+r"(r17),
+	    "+r"(r18),
+	    "+r"(t4),
+	    "+r"(ret0),
+	    "+r"(ret1),
+	    "+r"(r31)
+	    :: "memory");
+
+	error = posix_spawn(&pid, path, &fileacts, &attr, argv, envp);
+	if (error)
+		goto out;
+
+out:	posix_spawnattr_destroy(&attr);
+	posix_spawn_file_actions_destroy(&fileacts);
+	if (error) {
+		errno = error;
+		return -1;
+	}
+	return 0;
+}
diff --git a/kernel/arch/hppa/execregs.h b/kernel/arch/hppa/execregs.h
new file mode 100644
index 000000000000..ae4dbb2e39c0
--- /dev/null
+++ b/kernel/arch/hppa/execregs.h
@@ -0,0 +1,157 @@
+/*	$NetBSD: execregs.h,v 1.2 2025/02/28 16:08:19 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_HPPA_EXECREGS_H
+#define	TESTS_KERNEL_ARCH_HPPA_EXECREGS_H
+
+#include <sys/cdefs.h>
+
+#define	NEXECREGS	96
+
+#ifndef _LOCORE
+
+#include <unistd.h>
+
+/*
+ * Ordered by struct struct trapframe in sys/arch/hppa/include/frame.h
+ * for convenience of auditing.  Must match h_execregs.S.
+ */
+static const char *const regname[] = {
+	"t1",
+	"t2",
+	/* sp: stack pointer */
+	"t3",
+	/* various privileged stuff */
+	"sar",
+	"r1",
+	"rp",
+	/* r3: frame pointer (set to initial stack pointer) */
+	"r4",
+	"r5",
+	"r6",
+	"r70",
+	"r8",
+	"r9",
+	"r10",
+	"r11",
+	"r12",
+	"r13",
+	"r14",
+	"r15",
+	"r16",
+	"r17",
+	"r18",
+	"t4",
+	"arg3",
+	"arg2",
+	"arg1",
+	/* arg0: ps_strings */
+	"dp",
+	"ret0",
+	"ret1",
+	"r31",
+	"cr27",
+	"cr28",
+
+	"psw",	/* user-visible PSW bits: C/B and V */
+
+	/* Floating-point registers */
+	"fr0l",
+	"fr0r",
+	"fr1l",
+	"fr1r",
+	"fr2l",
+	"fr2r",
+	"fr3l",
+	"fr3r",
+	"fr4l",
+	"fr4r",
+	"fr5l",
+	"fr5r",
+	"fr6l",
+	"fr6r",
+	"fr7l",
+	"fr7r",
+	"fr8l",
+	"fr8r",
+	"fr9l",
+	"fr9r",
+	"fr10l",
+	"fr10r",
+	"fr11l",
+	"fr11r",
+	"fr12l",
+	"fr12r",
+	"fr13l",
+	"fr13r",
+	"fr14l",
+	"fr14r",
+	"fr15l",
+	"fr15r",
+	"fr16l",
+	"fr16r",
+	"fr17l",
+	"fr17r",
+	"fr18l",
+	"fr18r",
+	"fr19l",
+	"fr19r",
+	"fr20l",
+	"fr20r",
+	"fr21l",
+	"fr21r",
+	"fr22l",
+	"fr22r",
+	"fr23l",
+	"fr23r",
+	"fr24l",
+	"fr24r",
+	"fr25l",
+	"fr25r",
+	"fr26l",
+	"fr26r",
+	"fr27l",
+	"fr27r",
+	"fr28l",
+	"fr28r",
+	"fr29l",
+	"fr29r",
+	"fr30l",
+	"fr30r",
+	"fr31l",
+	"fr31r",
+};
+
+__CTASSERT(NEXECREGS == __arraycount(regname));
+
+int	execregschild(char *);
+pid_t	spawnregschild(char *, int);
+
+#endif	/* _LOCORE */
+
+#endif	/* TESTS_KERNEL_ARCH_HPPA_EXECREGS_H */
diff --git a/kernel/arch/hppa/execsp.S b/kernel/arch/hppa/execsp.S
new file mode 100644
index 000000000000..520421a1f1fc
--- /dev/null
+++ b/kernel/arch/hppa/execsp.S
@@ -0,0 +1,130 @@
+/*	$NetBSD: execsp.S,v 1.1 2025/04/20 22:32:49 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: execsp.S,v 1.1 2025/04/20 22:32:49 riastradh Exp $")
+
+	.import _GLOBAL_OFFSET_TABLE_
+
+/*
+ * void execsp_start(struct ps_strings *ps_strings@arg0,
+ *     void (*cleanup@arg1)(void), void *obj_main@arg2)
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ */
+LEAF_ENTRY(execsp_start)
+	/*
+	 * Set up the data pointer (r19) and linkage table register
+	 * (r27) like the real startup routine so we can get at the
+	 * global symbols startsp and __start.
+	 *
+	 * XXX Not really sure why we need to set up r27, since we only
+	 * use r19 here and the real startup routine, __start, will set
+	 * up both r19 and r27 anyway.  But this crashes with SIGSEGV
+	 * shortly after startup if we don't set up r27, and gdb
+	 * crashes on my attempts to single-step, so I'll just leave
+	 * the initialization of r27 here for now until someone is
+	 * motivated by the potential for a single-instruction
+	 * micro-optimization in this test program to find out why r27
+	 * is needed too.
+	 */
+	bl	L$lpc, %r27
+	 depi	0, 31, 2, %r27
+L$lpc:	addil	L'_GLOBAL_OFFSET_TABLE_ - ($PIC_pcrel$0 - 8), %r27
+	ldo	R'_GLOBAL_OFFSET_TABLE_ - ($PIC_pcrel$0 - 12)(%r1), %r27
+	copy	%r27, %r19
+
+	addil	LT%_C_LABEL(startsp), %r19	/* r20 := &startsp */
+	ldw	RT%_C_LABEL(startsp)(%r1), %r20
+
+	/* PIC_TAILCALL(__start), if we had it */
+	addil	LT%_C_LABEL(__start), %r19	/* r1 := __start */
+	ldw	RT%_C_LABEL(__start)(%r1), %r1
+	bv	%r0(%r1)			/* jump to __start */
+	 stw	%sp, 0(%r20)			/* startsp := sp */
+EXIT(execsp_start)
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+LEAF_ENTRY(execsp_ctor)
+	addil	LT%_C_LABEL(ctorsp), %r19	/* r1 := &ctorsp */
+	ldw	RT%_C_LABEL(ctorsp)(%r1), %r1
+	bv	%r0(%rp)			/* return */
+	 stw	%sp, 0(%r1)			/* ctorsp := sp */
+EXIT(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.section .ctors,"aw",@progbits
+	.p2align 2
+	.word	_C_LABEL(execsp_ctor)
+
+/*
+ * int main(int argc@arg0, char **argv@arg1, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+LEAF_ENTRY(main)
+	addil	LT%_C_LABEL(mainsp), %r19	/* r1 := &mainsp */
+	ldw	RT%_C_LABEL(mainsp)(%r1), %r1
+	stw	%sp, 0(%r1)			/* ctorsp := sp */
+	bv	%r0(%rp)			/* return... */
+	 copy	%r0, %ret0			/* ...zero */
+EXIT(main)
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+LEAF_ENTRY(execsp_dtor)
+	addil	LT%_C_LABEL(dtorsp), %r19	/* r20 := &dtorsp */
+	ldw	RT%_C_LABEL(dtorsp)(%r1), %r20
+
+	/* PIC_TAILCALL(__start), if we had it */
+	addil	LT%_C_LABEL(execsp_main), %r19	/* r1 := execsp_main */
+	ldw	RT%_C_LABEL(execsp_main)(%r1), %r1
+	bv	%r0(%r1)			/* jump to execsp_main */
+	 stw	%sp, 0(%r20)			/* startsp := sp */
+EXIT(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.section .dtors,"aw",@progbits
+	.p2align 2
+	.word	_C_LABEL(execsp_dtor)
diff --git a/kernel/arch/hppa/h_execregs.S b/kernel/arch/hppa/h_execregs.S
new file mode 100644
index 000000000000..ad7a50a5b932
--- /dev/null
+++ b/kernel/arch/hppa/h_execregs.S
@@ -0,0 +1,168 @@
+/*	$NetBSD: h_execregs.S,v 1.2 2025/02/28 16:08:19 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <sys/syscall.h>
+
+#include <machine/asm.h>
+#include <machine/vmparam.h>
+
+#include "execregs.h"
+
+_ENTRY(execregs_start)
+	.callinfo frame=(NEXECREGS*4), calls
+	.entry
+
+	ldo	(NEXECREGS*4)(%sp), %sp		/* space for NEXECREGS */
+	stw	%t1, (4*(0 - NEXECREGS))(%sp)	/* order matches execregs.h */
+	stw	%t2, (4*(1 - NEXECREGS))(%sp)
+	/* sp: stack pointer */
+	stw	%t3, (4*(2 - NEXECREGS))(%sp)
+	/* cr17/iisq_head: privileged */
+	/* cr17/iisq_tail: privileged */
+	/* cr18/iioq_head: privileged */
+	/* cr18/iioq_tail: privileged */
+	/* cr15/eiem: privileged */
+	/* cr22/ipsw: privileged */
+	/* sr3: privileged(?) */
+	/* cr8/pidr1: privileged */
+	/* cr20/isr: privileged */
+	/* cr21/ior: privileged */
+	/* cr19/iir: privileged */
+	/* flags: N/A(?) */
+	stw	%sar, (4*(3 - NEXECREGS))(%sp)
+	stw	%r1, (4*(4 - NEXECREGS))(%sp)
+	stw	%rp, (4*(5 - NEXECREGS))(%sp)
+	/* r3: frame pointer (set to initial stack pointer) */
+	stw	%r4, (4*(6 - NEXECREGS))(%sp)
+	stw	%r5, (4*(7 - NEXECREGS))(%sp)
+	stw	%r6, (4*(8 - NEXECREGS))(%sp)
+	stw	%r7, (4*(9 - NEXECREGS))(%sp)
+	stw	%r8, (4*(10 - NEXECREGS))(%sp)
+	stw	%r9, (4*(11 - NEXECREGS))(%sp)
+	stw	%r10, (4*(12 - NEXECREGS))(%sp)
+	stw	%r11, (4*(13 - NEXECREGS))(%sp)
+	stw	%r12, (4*(14 - NEXECREGS))(%sp)
+	stw	%r13, (4*(15 - NEXECREGS))(%sp)
+	stw	%r14, (4*(16 - NEXECREGS))(%sp)
+	stw	%r15, (4*(17 - NEXECREGS))(%sp)
+	stw	%r16, (4*(18 - NEXECREGS))(%sp)
+	stw	%r17, (4*(19 - NEXECREGS))(%sp)
+	stw	%r18, (4*(20 - NEXECREGS))(%sp)
+	stw	%t4, (4*(21 - NEXECREGS))(%sp)
+	stw	%arg3, (4*(22 - NEXECREGS))(%sp)
+	stw	%arg2, (4*(23 - NEXECREGS))(%sp)
+	stw	%arg1, (4*(24 - NEXECREGS))(%sp)
+	/* arg0: ps_strings */
+	stw	%dp, (4*(25 - NEXECREGS))(%sp)
+	stw	%ret0, (4*(26 - NEXECREGS))(%sp)
+	stw	%ret1, (4*(27 - NEXECREGS))(%sp)
+	stw	%r31, (4*(28 - NEXECREGS))(%sp)
+	/* sr0-sr7: space registers initialized by kernel */
+	/* cr9/pidr2: privileged */
+	/* cr12/pidr3: privileged */
+	/* cr13/pidr4: privileged */
+	/* cr0/rctr: privileged */
+	/* cr10/ccr: privileged */
+	/* cr23/eirr: privileged */
+	/* cr24: privileged */
+	/* cr25/vtop: privileged */
+	/* cr26: ??? */
+	stw	%cr27, (4*(29 - NEXECREGS))(%sp)
+	stw	%cr28, (4*(30 - NEXECREGS))(%sp)
+	/* cr30/fpregs: privileged */
+	/* cr31: privileged */
+
+	addc	%t1, %r0, %r0	/* t1 := PSW[C/B]{0} */
+	zdep	%t1, 23, 8, %t1	/* t1 := PSW */
+	stw	%t1, (4*(31 - NEXECREGS))(%sp)
+
+	/* store the fp registers */
+	ldo	(4*(32 - NEXECREGS))(%sp), %t1
+	fstd,ma	%fr0, 8(%t1)
+	fstd,ma	%fr1, 8(%t1)
+	fstd,ma	%fr2, 8(%t1)
+	fstd,ma	%fr3, 8(%t1)
+	fstd,ma	%fr4, 8(%t1)
+	fstd,ma	%fr5, 8(%t1)
+	fstd,ma	%fr6, 8(%t1)
+	fstd,ma	%fr7, 8(%t1)
+	fstd,ma	%fr8, 8(%t1)
+	fstd,ma	%fr9, 8(%t1)
+	fstd,ma	%fr10, 8(%t1)
+	fstd,ma	%fr11, 8(%t1)
+	fstd,ma	%fr12, 8(%t1)
+	fstd,ma	%fr13, 8(%t1)
+	fstd,ma	%fr14, 8(%t1)
+	fstd,ma	%fr15, 8(%t1)
+	fstd,ma	%fr16, 8(%t1)
+	fstd,ma	%fr17, 8(%t1)
+	fstd,ma	%fr18, 8(%t1)
+	fstd,ma	%fr19, 8(%t1)
+	fstd,ma	%fr20, 8(%t1)
+	fstd,ma	%fr21, 8(%t1)
+	fstd,ma	%fr22, 8(%t1)
+	fstd,ma	%fr23, 8(%t1)
+	fstd,ma	%fr24, 8(%t1)
+	fstd,ma	%fr25, 8(%t1)
+	fstd,ma	%fr26, 8(%t1)
+	fstd,ma	%fr27, 8(%t1)
+	fstd,ma	%fr28, 8(%t1)
+	fstd,ma	%fr29, 8(%t1)
+	fstd,ma	%fr30, 8(%t1)
+	fstd	%fr31, 0(%t1)
+
+	/* call write(STDOUT_FILENO, regs, sizeof(regs)) */
+	ldi	1, %arg0			/* arg0 := STDOUT_FILENO */
+	ldo	-(4*NEXECREGS)(%sp), %arg1	/* arg1 := regs */
+	ldi	(4*NEXECREGS), %arg2		/* arg2 := sizeof(regs) */
+	ldil	L%SYSCALLGATE, %r1
+	ble	4(%sr2, %r1)
+	 ldi	SYS_write, %t1
+
+	comb,<>,n	%r0, %t1, 2f		/* bail if write failed */
+	ldi		(4*NEXECREGS), %t1	/* bail if wrong # bytes */
+	comb,<>,n	%ret0, %t1, 2f
+
+	/* call exit(0) */
+	ldi	0, %arg0
+1:	ldil	L%SYSCALLGATE, %r1
+	ble	4(%sr2, %r1)
+	 ldi	SYS_exit, %t1
+	break	0, 0				/* paranoia */
+
+2:	/* call exit(127) */
+	b	1b
+	 ldi	127, %arg0
+EXIT(execregs_start)
+
+/* main stub to simplify linking */
+LEAF_ENTRY(main)
+	break	0, 0				/* paranoia */
+EXIT(main)
diff --git a/kernel/arch/hppa/signalsphandler.S b/kernel/arch/hppa/signalsphandler.S
new file mode 100644
index 000000000000..01633d99ff8b
--- /dev/null
+++ b/kernel/arch/hppa/signalsphandler.S
@@ -0,0 +1,46 @@
+/*	$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:32:49 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:32:49 riastradh Exp $")
+
+/*
+ * signalsphandler(signo@arg0)
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+LEAF_ENTRY(signalsphandler)
+	addil	LT%_C_LABEL(signalsp), %r19	/* r1 := &signalsp */
+	ldw	RT%_C_LABEL(signalsp)(%r1), %r1
+	bv	%r0(%rp)			/* return */
+	 stw	%sp, 0(%r1)			/* signalsp := sp */
+EXIT(signalsphandler)
diff --git a/kernel/arch/hppa/stack_pointer.h b/kernel/arch/hppa/stack_pointer.h
new file mode 100644
index 000000000000..acb73443621c
--- /dev/null
+++ b/kernel/arch/hppa/stack_pointer.h
@@ -0,0 +1,35 @@
+/*	$NetBSD: stack_pointer.h,v 1.1 2025/04/20 22:32:49 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_HPPA_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_HPPA_STACK_POINTER_H
+
+#define MISALIGN_SP	__asm __volatile("ldo 1(%%sp),%%sp" ::: "memory")
+#define FIX_SP		__asm __volatile("ldo -1(%%sp),%%sp" ::: "memory")
+
+#endif	/* TESTS_KERNEL_ARCH_HPPA_STACK_POINTER_H */
diff --git a/kernel/arch/hppa/threadspfunc.S b/kernel/arch/hppa/threadspfunc.S
new file mode 100644
index 000000000000..f1b1d21fadfe
--- /dev/null
+++ b/kernel/arch/hppa/threadspfunc.S
@@ -0,0 +1,43 @@
+/*	$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $")
+
+/*
+ * void *threadspfunc(void *cookie@arg0)
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+LEAF_ENTRY(threadspfunc)
+	bv	%r0(%rp)			/* return to caller */
+	 copy	%sp, %ret0			/* return sp */
+EXIT(threadspfunc)
diff --git a/kernel/arch/i386/contextspfunc.S b/kernel/arch/i386/contextspfunc.S
new file mode 100644
index 000000000000..cc097cc61325
--- /dev/null
+++ b/kernel/arch/i386/contextspfunc.S
@@ -0,0 +1,56 @@
+/*	$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $")
+
+/*
+ * contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+ENTRY(contextspfunc)
+	call	getpc_eax
+	addl	$_GLOBAL_OFFSET_TABLE_,%eax
+	movl	_C_LABEL(contextsp)@GOT(%eax),%eax
+	movl	%esp,(%eax)
+	jmp	_C_LABEL(contextdone)@PLT
+END(contextspfunc)
+
+	.text
+	_ALIGN_TEXT
+	.local	getpc_eax
+	.type	getpc_eax,@function
+getpc_eax:
+	movl	(%esp),%eax
+	ret
+END(getpc_eax)
diff --git a/kernel/arch/i386/execregs.c b/kernel/arch/i386/execregs.c
new file mode 100644
index 000000000000..477cd82989e9
--- /dev/null
+++ b/kernel/arch/i386/execregs.c
@@ -0,0 +1,132 @@
+/*	$NetBSD: execregs.c,v 1.1 2025/02/27 00:55:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: execregs.c,v 1.1 2025/02/27 00:55:32 riastradh Exp $");
+
+#include "execregs.h"
+
+#include <errno.h>
+#include <spawn.h>
+#include <stddef.h>
+#include <unistd.h>
+
+extern char **environ;
+
+static unsigned long
+nonnull(unsigned long x)
+{
+
+	x |= x << 8;
+	x |= x << 16;
+	return x;
+}
+
+int
+execregschild(char *path)
+{
+	register long edi __asm("edi") = nonnull('d');
+	register long esi __asm("esi") = nonnull('s');
+	/* ebp: frame pointer, can't touch that here, but it'll be nonnull */
+	/* ebx: ps_strings, passed to child */
+	register long edx __asm("edx") = nonnull('x');
+	register long ecx __asm("ecx") = nonnull('c');
+	register long eax __asm("eax") = nonnull('a');
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("" :
+	    "+r"(edi),
+	    "+r"(esi),
+	    "+r"(edx),
+	    "+r"(ecx),
+	    "+r"(eax)
+	    :: "memory");
+
+	return execve(path, argv, envp);
+}
+
+pid_t
+spawnregschild(char *path, int fd)
+{
+	register long edi __asm("edi") = nonnull('d');
+	register long esi __asm("esi") = nonnull('s');
+	/* ebp: frame pointer, can't touch that here, but it'll be nonnull */
+	/* ebx: ps_strings, passed to child */
+	register long edx __asm("edx") = nonnull('x');
+	register long ecx __asm("ecx") = nonnull('c');
+	register long eax __asm("eax") = nonnull('a');
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+	posix_spawn_file_actions_t fileacts;
+	posix_spawnattr_t attr;
+	pid_t pid;
+	int error;
+
+	error = posix_spawn_file_actions_init(&fileacts);
+	if (error)
+		goto out;
+	error = posix_spawn_file_actions_adddup2(&fileacts, fd, STDOUT_FILENO);
+	if (error)
+		goto out;
+	error = posix_spawnattr_init(&attr);
+	if (error)
+		goto out;
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("" :
+	    "+r"(edi),
+	    "+r"(esi),
+	    "+r"(edx),
+	    "+r"(ecx),
+	    "+r"(eax)
+	    :: "memory");
+
+	error = posix_spawn(&pid, path, &fileacts, &attr, argv, envp);
+	if (error)
+		goto out;
+
+out:	posix_spawnattr_destroy(&attr);
+	posix_spawn_file_actions_destroy(&fileacts);
+	if (error) {
+		errno = error;
+		return -1;
+	}
+	return 0;
+}
diff --git a/kernel/arch/i386/execregs.h b/kernel/arch/i386/execregs.h
new file mode 100644
index 000000000000..f512bbabc1c7
--- /dev/null
+++ b/kernel/arch/i386/execregs.h
@@ -0,0 +1,69 @@
+/*	$NetBSD: execregs.h,v 1.1 2025/02/27 00:55:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_I386_EXECREGS_H
+#define	TESTS_KERNEL_ARCH_I386_EXECREGS_H
+
+#include <sys/cdefs.h>
+
+#define	NEXECREGS	6
+
+#ifndef _LOCORE
+
+#include <unistd.h>
+
+/*
+ * Ordered by struct trapframe in sys/arch/i386/include/frame.h for
+ * convenience of auditing.  Must match h_execregs.S.
+ */
+static const char *const regname[] = {
+	/* gs/fs/es/ds: segment registers, not really registers */
+	"edi",
+	"esi",
+	"ebp",
+	/* ebx: ps_strings */
+	"edx",
+	"ecx",
+	"eax",
+	/* trapno: not a register */
+	/* err: not a register */
+	/* eip: instruction pointer */
+	/* cs: segment register */
+	/* eflags */
+	/* esp: stack pointer */
+	/* ss: stack selector */
+};
+
+__CTASSERT(NEXECREGS == __arraycount(regname));
+
+int	execregschild(char *);
+pid_t	spawnregschild(char *, int);
+
+#endif	/* _LOCORE */
+
+#endif	/* TESTS_KERNEL_ARCH_I386_EXECREGS_H */
diff --git a/kernel/arch/i386/execsp.S b/kernel/arch/i386/execsp.S
new file mode 100644
index 000000000000..133af37715ad
--- /dev/null
+++ b/kernel/arch/i386/execsp.S
@@ -0,0 +1,112 @@
+/*	$NetBSD: execsp.S,v 1.1 2025/04/20 22:33:13 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: execsp.S,v 1.1 2025/04/20 22:33:13 riastradh Exp $")
+
+/*
+ * void execsp_start(void (*cleanup@edx)(void), void *obj_main@ecx,
+ *     struct ps_strings *ps_strings@ebx)
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ */
+ENTRY(execsp_start)
+	call	getpc_eax
+	addl	$_GLOBAL_OFFSET_TABLE_,%eax
+	movl	_C_LABEL(startsp)@GOT(%eax),%eax
+	movl	%esp,(%eax)
+	jmp	_C_LABEL(__start)@PLT
+END(execsp_start)
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+ENTRY(execsp_ctor)
+	call	getpc_eax
+	addl	$_GLOBAL_OFFSET_TABLE_,%eax
+	movl	_C_LABEL(ctorsp)@GOT(%eax),%eax
+	movl	%esp,(%eax)
+	ret
+END(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.section .ctors,"aw",@progbits
+	.p2align 2
+	.long	_C_LABEL(execsp_ctor)
+
+/*
+ * int main(int argc@rdi, char **argv@rsi, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+ENTRY(main)
+	call	getpc_eax
+	addl	$_GLOBAL_OFFSET_TABLE_,%eax
+	movl	_C_LABEL(mainsp)@GOT(%eax),%eax
+	movl	%esp,(%eax)
+	xorl	%eax,%eax
+	ret
+END(main)
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+ENTRY(execsp_dtor)
+	call	getpc_eax
+	addl	$_GLOBAL_OFFSET_TABLE_,%eax
+	movl	_C_LABEL(dtorsp)@GOT(%eax),%eax
+	movl	%esp,(%eax)
+	jmp	_C_LABEL(execsp_main)@PLT
+END(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.section .dtors,"aw",@progbits
+	.p2align 2
+	.long	_C_LABEL(execsp_dtor)
+
+	.text
+	_ALIGN_TEXT
+	.local	getpc_eax
+	.type	getpc_eax,@function
+getpc_eax:
+	movl	(%esp),%eax
+	ret
+END(getpc_eax)
diff --git a/kernel/arch/i386/h_execregs.S b/kernel/arch/i386/h_execregs.S
new file mode 100644
index 000000000000..ac9b843f9d86
--- /dev/null
+++ b/kernel/arch/i386/h_execregs.S
@@ -0,0 +1,85 @@
+/*	$NetBSD: h_execregs.S,v 1.1 2025/02/27 00:55:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <sys/syscall.h>
+
+#include <machine/asm.h>
+
+#include "execregs.h"
+
+ENTRY(execregs_start)
+	andl	$-0x4,%esp		/* align stack to 4-byte boundary */
+
+	/* store registers to a buffer on stack */
+	subl	$(NEXECREGS*4),%esp	/* space for NEXECREGS registers */
+	movl	%edi,0*4(%esp)		/* order matches execregs.h */
+	movl	%esi,1*4(%esp)
+	movl	%ebp,2*4(%esp)
+	movl	%edx,3*4(%esp)
+	movl	%ecx,4*4(%esp)
+	movl	%eax,5*4(%esp)
+
+	/* call write(STDOUT_FILENO, regs, sizeof(regs)) */
+	movl	%esp,%eax		/* eax := regs */
+	pushl	$(NEXECREGS*4)		/* arg2 := sizeof(regs) */
+	pushl	%eax			/* arg1 := regs */
+	pushl	$0x1			/* arg0 := STDOUT_FILENO */
+	call	execregs_write
+
+	jb	2f			/* bail if write failed */
+	cmpl	$(NEXECREGS*4),%eax	/* bail if wrote wrong # of bytes */
+	jne	2f
+
+	/* call exit(0) */
+	pushl	$0			/* arg0 := 0 */
+1:	call	execregs_exit
+	hlt				/* paranoia */
+
+2:	/* call exit(127) */
+	pushl	$127			/* arg0 := 127 */
+	jmp	1b
+END(execregs_start)
+
+ENTRY(execregs_write)
+	movl	$SYS_write,%eax		/* syscall number */
+	int	$0x80
+	retl
+END(execregs_write)
+
+ENTRY(execregs_exit)
+	movl	$SYS_exit,%eax		/* syscall number */
+	int	$0x80
+	hlt
+END(execregs_exit)
+
+/* main stub to simplify linking */
+ENTRY(main)
+	hlt
+END(main)
diff --git a/kernel/arch/i386/signalsphandler.S b/kernel/arch/i386/signalsphandler.S
new file mode 100644
index 000000000000..418825e78ab6
--- /dev/null
+++ b/kernel/arch/i386/signalsphandler.S
@@ -0,0 +1,56 @@
+/*	$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:33:13 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:33:13 riastradh Exp $")
+
+/*
+ * signalsphandler(signo@esp[4])
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+ENTRY(signalsphandler)
+	call	getpc_eax
+	addl	$_GLOBAL_OFFSET_TABLE_,%eax
+	movl	_C_LABEL(signalsp)@GOT(%eax),%eax
+	movl	%esp,(%eax)
+	ret
+END(signalsphandler)
+
+	.text
+	_ALIGN_TEXT
+	.local	getpc_eax
+	.type	getpc_eax,@function
+getpc_eax:
+	movl	(%esp),%eax
+	ret
+END(getpc_eax)
diff --git a/kernel/arch/i386/stack_pointer.h b/kernel/arch/i386/stack_pointer.h
new file mode 100644
index 000000000000..6c95a28ab7b6
--- /dev/null
+++ b/kernel/arch/i386/stack_pointer.h
@@ -0,0 +1,35 @@
+/*	$NetBSD: stack_pointer.h,v 1.1 2025/04/20 22:33:13 riastradh Exp $	*/
+
+/*
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_I386_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_I386_STACK_POINTER_H
+
+#define MISALIGN_SP	__asm __volatile("addl $-1,%esp")
+#define FIX_SP		__asm __volatile("addl $1,%esp")
+
+#endif	/* TESTS_KERNEL_ARCH_I386_STACK_POINTER_H */
diff --git a/kernel/arch/i386/threadspfunc.S b/kernel/arch/i386/threadspfunc.S
new file mode 100644
index 000000000000..af03ff4c550e
--- /dev/null
+++ b/kernel/arch/i386/threadspfunc.S
@@ -0,0 +1,43 @@
+/*	$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $")
+
+/*
+ * void *threadspfunc(void *cookie@esp[4])
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+ENTRY(threadspfunc)
+	mov	%esp,%eax
+	ret
+END(threadspfunc)
diff --git a/kernel/arch/mips/contextspfunc.S b/kernel/arch/mips/contextspfunc.S
new file mode 100644
index 000000000000..bee0a610dc86
--- /dev/null
+++ b/kernel/arch/mips/contextspfunc.S
@@ -0,0 +1,53 @@
+/*	$NetBSD: contextspfunc.S,v 1.2 2025/04/27 16:49:54 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: contextspfunc.S,v 1.2 2025/04/27 16:49:54 riastradh Exp $")
+
+#include "SYS.h"
+
+	.text
+
+/*
+ * contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+LEAF(contextspfunc)
+	PIC_PROLOGUE(contextspfunc)	/* gp setup, sets t3 */
+
+	PTR_LA	t1, _C_LABEL(contextsp)	/* load t1 := &contextsp */
+	 NOP_L				/* load hazard */
+	PTR_S	sp, 0(t1)		/* store contextsp := stack pointer */
+
+	PIC_TAILCALL(contextdone)
+END(contextspfunc)
diff --git a/kernel/arch/mips/execsp.S b/kernel/arch/mips/execsp.S
new file mode 100644
index 000000000000..b4f2dcfd6e2c
--- /dev/null
+++ b/kernel/arch/mips/execsp.S
@@ -0,0 +1,118 @@
+/*	$NetBSD: execsp.S,v 1.2 2025/04/27 16:49:54 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: execsp.S,v 1.2 2025/04/27 16:49:54 riastradh Exp $")
+
+#include "SYS.h"
+
+	.text
+
+/*
+ * void execsp_start(void *stackpointer@a0, void (*cleanup@a1)(void),
+ *     void *obj_main@a2, struct ps_strings *ps_strings@a3)
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ */
+LEAF(execsp_start)
+	PIC_PROLOGUE(execsp_start)	/* gp setup, sets t3 */
+
+	PTR_LA	t1, _C_LABEL(startsp)	/* load t1 := &startsp */
+	 NOP_L				/* load hazard */
+	PTR_S	sp, 0(t1)		/* store startsp := stack pointer */
+
+	PIC_TAILCALL(__start)		/* gp restore, uses t3 */
+END(execsp_start)
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+LEAF(execsp_ctor)
+	PIC_PROLOGUE(execsp_ctor)	/* gp setup, sets t3 */
+
+	PTR_LA	t1, _C_LABEL(ctorsp)	/* load t1 := &ctorsp */
+	 NOP_L				/* load hazard */
+	PTR_S	sp, 0(t1)		/* store ctorsp := stack pointer */
+
+	PIC_RETURN()			/* gp restore, uses t3 */
+END(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.pushsection .ctors,"aw",@progbits
+	.p2align PTR_SCALESHIFT
+	PTR_WORD	_C_LABEL(execsp_ctor)
+	.popsection
+
+/*
+ * int main(int argc@a0, char **argv@a1, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+LEAF(main)
+	PIC_PROLOGUE(main)		/* gp setup, sets t3 */
+
+	PTR_LA	t1, _C_LABEL(mainsp)	/* load t1 := &mainsp */
+	 NOP_L				/* load hazard */
+	PTR_S	sp, 0(t1)		/* store mainsp := stack pointer */
+
+	move	v0, zero		/* return 0 */
+
+	PIC_RETURN()			/* gp restore, uses t3 */
+END(main)
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+LEAF(execsp_dtor)
+	PIC_PROLOGUE(execsp_dtor)	/* gp setup, sets t3 */
+
+	PTR_LA	t1, _C_LABEL(dtorsp)	/* load t1 := &dtorsp */
+	 NOP_L				/* load hazard */
+	PTR_S	sp, 0(t1)		/* store dtorsp := stack pointer */
+
+	PIC_TAILCALL(execsp_main)	/* gp restore, uses t3 */
+END(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.pushsection .dtors,"aw",@progbits
+	.p2align PTR_SCALESHIFT
+	PTR_WORD	_C_LABEL(execsp_dtor)
+	.popsection
diff --git a/kernel/arch/mips/signalsphandler.S b/kernel/arch/mips/signalsphandler.S
new file mode 100644
index 000000000000..e742c2c95701
--- /dev/null
+++ b/kernel/arch/mips/signalsphandler.S
@@ -0,0 +1,53 @@
+/*	$NetBSD: signalsphandler.S,v 1.2 2025/04/27 16:49:54 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: signalsphandler.S,v 1.2 2025/04/27 16:49:54 riastradh Exp $")
+
+#include "SYS.h"
+
+	.text
+
+/*
+ * signalsphandler(signo@a0)
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+LEAF(signalsphandler)
+	PIC_PROLOGUE(signalsphandler)	/* gp setup, sets t3 */
+
+	PTR_LA	t1, _C_LABEL(signalsp)	/* load t1 := &signalsp */
+	 NOP_L				/* load hazard */
+	PTR_S	sp, 0(t1)		/* store signalsp := stack pointer */
+
+	PIC_RETURN()
+END(signalsphandler)
diff --git a/kernel/arch/mips/stack_pointer.h b/kernel/arch/mips/stack_pointer.h
new file mode 100644
index 000000000000..288c58928526
--- /dev/null
+++ b/kernel/arch/mips/stack_pointer.h
@@ -0,0 +1,40 @@
+/*	$NetBSD: stack_pointer.h,v 1.2 2025/04/21 14:17:38 rin Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_MIPS_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_MIPS_STACK_POINTER_H
+
+#ifdef __mips_o32
+#define MISALIGN_SP	__asm __volatile("addiu $sp,$sp,-1" ::: "memory")
+#define FIX_SP		__asm __volatile("addiu $sp,$sp,1" ::: "memory")
+#else
+#define MISALIGN_SP	__asm __volatile("daddiu $sp,$sp,-1" ::: "memory")
+#define FIX_SP		__asm __volatile("daddiu $sp,$sp,1" ::: "memory")
+#endif
+
+#endif	/* TESTS_KERNEL_ARCH_MIPS_STACK_POINTER_H */
diff --git a/kernel/arch/mips/threadspfunc.S b/kernel/arch/mips/threadspfunc.S
new file mode 100644
index 000000000000..a42362fee67d
--- /dev/null
+++ b/kernel/arch/mips/threadspfunc.S
@@ -0,0 +1,46 @@
+/*	$NetBSD: threadspfunc.S,v 1.2 2025/04/21 03:47:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: threadspfunc.S,v 1.2 2025/04/21 03:47:32 riastradh Exp $")
+
+	.text
+	.set noreorder
+
+/*
+ * void *threadspfunc(void *cookie@a0)
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+LEAF(threadspfunc)
+	j	ra
+	 move	v0, sp
+END(threadspfunc)
diff --git a/kernel/arch/riscv/contextspfunc.S b/kernel/arch/riscv/contextspfunc.S
new file mode 100644
index 000000000000..7f405123deb3
--- /dev/null
+++ b/kernel/arch/riscv/contextspfunc.S
@@ -0,0 +1,45 @@
+/*	$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $")
+
+/*
+ * contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+ENTRY(contextspfunc)
+	PTR_LA	t0, _C_LABEL(contextsp)	/* t0 := &contextsp */
+	PTR_S	sp, 0(t0)		/* contextsp := sp */
+	tail	_C_LABEL(contextdone)	/* tail call contextdone */
+END(contextspfunc)
diff --git a/kernel/arch/riscv/execsp.S b/kernel/arch/riscv/execsp.S
new file mode 100644
index 000000000000..d045cbf0d3af
--- /dev/null
+++ b/kernel/arch/riscv/execsp.S
@@ -0,0 +1,100 @@
+/*	$NetBSD: execsp.S,v 1.1 2025/04/20 22:34:07 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: execsp.S,v 1.1 2025/04/20 22:34:07 riastradh Exp $")
+
+/*
+ * void execsp_start(void (*cleanup@a0)(void),
+ *     struct ps_strings *ps_strings@a1)
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ */
+ENTRY(execsp_start)
+	.option push
+	.option norelax		/* Don't optimize this into `mv gp, gp'! */
+	lla	gp, __global_pointer$
+	.option pop
+
+	PTR_LA	t0, _C_LABEL(startsp)	/* t0 := &startsp */
+	PTR_S	sp, 0(t0)		/* startsp := sp */
+	tail	_C_LABEL(__start)	/* tail call __start */
+END(execsp_start)
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+ENTRY(execsp_ctor)
+	PTR_LA	t0, _C_LABEL(ctorsp)	/* t0 := &ctorsp */
+	PTR_S	sp, 0(t0)		/* ctorsp := sp */
+	ret
+END(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.section .init_array,"aw"
+	.p2align PTR_SCALESHIFT
+	PTR_WORD	_C_LABEL(execsp_ctor)
+
+/*
+ * int main(int argc@a0, char **argv@a1, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+ENTRY(main)
+	PTR_LA	t0, _C_LABEL(mainsp)	/* t0 := &mainsp */
+	PTR_S	sp, 0(t0)		/* mainsp := sp */
+	li	a0, 0			/* return 0 */
+	ret
+END(main)
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+ENTRY(execsp_dtor)
+	PTR_LA	t0, _C_LABEL(dtorsp)	/* t0 := &dtorsp */
+	PTR_S	sp, 0(t0)		/* dtorsp := sp */
+	tail	_C_LABEL(execsp_main)	/* tail call execsp_main */
+END(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.section .fini_array,"aw"
+	.p2align PTR_SCALESHIFT
+	PTR_WORD	_C_LABEL(execsp_dtor)
diff --git a/kernel/arch/riscv/signalsphandler.S b/kernel/arch/riscv/signalsphandler.S
new file mode 100644
index 000000000000..6a5d2f752ee2
--- /dev/null
+++ b/kernel/arch/riscv/signalsphandler.S
@@ -0,0 +1,45 @@
+/*	$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:34:07 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:34:07 riastradh Exp $")
+
+/*
+ * signalsphandler(signo@a0)
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+ENTRY(signalsphandler)
+	PTR_LA	t0, _C_LABEL(signalsp)	/* t0 := &signalsp */
+	PTR_S	sp, 0(t0)		/* signalsp := sp */
+	ret
+END(signalsphandler)
diff --git a/kernel/arch/riscv/stack_pointer.h b/kernel/arch/riscv/stack_pointer.h
new file mode 100644
index 000000000000..22c246e4a86a
--- /dev/null
+++ b/kernel/arch/riscv/stack_pointer.h
@@ -0,0 +1,35 @@
+/*	$NetBSD: stack_pointer.h,v 1.1 2025/04/20 22:34:07 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_RISCV_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_RISCV_STACK_POINTER_H
+
+#define MISALIGN_SP	__asm __volatile("addi sp,sp,-1" ::: "memory")
+#define FIX_SP		__asm __volatile("addi sp,sp,1" ::: "memory")
+
+#endif	/* TESTS_KERNEL_ARCH_RISCV_STACK_POINTER_H */
diff --git a/kernel/arch/riscv/threadspfunc.S b/kernel/arch/riscv/threadspfunc.S
new file mode 100644
index 000000000000..30291ad2eb73
--- /dev/null
+++ b/kernel/arch/riscv/threadspfunc.S
@@ -0,0 +1,43 @@
+/*	$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:44 riastradh Exp $")
+
+/*
+ * void *threadspfunc(void *cookie@o0)
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+ENTRY(threadspfunc)
+	mv	a0, sp			/* return sp */
+	ret				/* return to caller */
+END(threadspfunc)
diff --git a/kernel/arch/sh3/asm.h b/kernel/arch/sh3/asm.h
new file mode 100644
index 000000000000..16389b5c299e
--- /dev/null
+++ b/kernel/arch/sh3/asm.h
@@ -0,0 +1,58 @@
+/*	$NetBSD: asm.h,v 1.1 2025/04/26 22:34:52 uwe Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_SH3_ASM_H
+#define	TESTS_KERNEL_ARCH_SH3_ASM_H
+
+#include <machine/asm.h>
+
+/*
+ * We define convenience macros to hide the difference between direct
+ * and PIC function calls, but with variable accesses it gets a bit
+ * more unwieldy, so don't impose this on the general audience
+ */
+
+#ifdef __PIC__
+
+#define VAR_DATUM(v)	.long	v@GOT
+
+#define MOVL_VAR(label, reg)		\
+		mov.l	label, r0;	\
+		mov.l	@(r0, r12), reg
+
+#else
+
+#define VAR_DATUM(v)	.long	v
+
+#define MOVL_VAR(label, reg)		\
+		mov.l	label, reg;	\
+
+#endif
+
+
+#endif	/* TESTS_KERNEL_ARCH_SH3_ASM_H */
diff --git a/kernel/arch/sh3/contextspfunc.S b/kernel/arch/sh3/contextspfunc.S
new file mode 100644
index 000000000000..51e91133417e
--- /dev/null
+++ b/kernel/arch/sh3/contextspfunc.S
@@ -0,0 +1,55 @@
+/*	$NetBSD: contextspfunc.S,v 1.1 2025/04/26 22:34:52 uwe Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "asm.h"
+
+RCSID("$NetBSD: contextspfunc.S,v 1.1 2025/04/26 22:34:52 uwe Exp $")
+
+
+/*
+ * void contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+ENTRY(contextspfunc)
+	mov	sp, r1
+	PIC_PROLOGUE(.L_GOT)
+
+	MOVL_VAR(.L_contextsp, r0)
+	mov.l	r1, @r0
+
+	mov.l	.L_contextdone, r0
+1:	JUMP	r0
+	 PIC_EPILOGUE_SLOT
+
+	.p2align 2
+.L_GOT:		PIC_GOT_DATUM
+.L_contextsp:	VAR_DATUM(contextsp)
+.L_contextdone:	CALL_DATUM(contextdone, 1b)
+	SET_ENTRY_SIZE(contextspfunc)
diff --git a/kernel/arch/sh3/execsp.S b/kernel/arch/sh3/execsp.S
new file mode 100644
index 000000000000..639ed4e6487b
--- /dev/null
+++ b/kernel/arch/sh3/execsp.S
@@ -0,0 +1,146 @@
+/*	$NetBSD: execsp.S,v 1.2 2025/04/27 00:03:46 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "asm.h"
+
+RCSID("$NetBSD: execsp.S,v 1.2 2025/04/27 00:03:46 riastradh Exp $")
+
+
+/*
+ * void execsp_start()
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ *
+ *	See sys/arch/sh3/sh3/sh3_machdep.c setregs()
+ */
+ENTRY(execsp_start)
+	mov	sp, r1	// for consistency, don't need to
+	PIC_PROLOGUE_NOSAVE(.L_start_GOT)
+
+	MOVL_VAR(.L_startsp, r0)
+	mov.l	r1, @r0
+
+	mov.l	.L___start, r0
+1:	JUMP	r0
+	 nop
+
+	.p2align 2
+.L_start_GOT:	PIC_GOT_DATUM
+.L_startsp:	VAR_DATUM(startsp)
+.L___start:	CALL_DATUM(__start, 1b)
+	SET_ENTRY_SIZE(execsp_start)
+
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+ENTRY(execsp_ctor)
+	mov	sp, r1
+	PIC_PROLOGUE(.L_ctor_GOT)
+
+	MOVL_VAR(.L_ctorsp, r0)
+	mov.l	r1, @r0
+
+	rts
+	 PIC_EPILOGUE_SLOT
+
+	.p2align 2
+.L_ctor_GOT:	PIC_GOT_DATUM
+.L_ctorsp:	VAR_DATUM(ctorsp)
+	SET_ENTRY_SIZE(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.pushsection .ctors, "aw", @progbits
+	.p2align 2
+	.long	_C_LABEL(execsp_ctor)
+	.popsection
+
+
+/*
+ * int main(int argc, char **argv, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+ENTRY(main)
+	mov	sp, r1
+	PIC_PROLOGUE(.L_main_GOT)
+
+	MOVL_VAR(.L_mainsp, r0)
+	mov.l	r1, @r0
+
+	PIC_EPILOGUE
+	rts
+	 mov	#0, r0
+
+	.p2align 2
+.L_main_GOT:	PIC_GOT_DATUM
+.L_mainsp:	VAR_DATUM(mainsp)
+	SET_ENTRY_SIZE(main)
+
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+ENTRY(execsp_dtor)
+	mov	sp, r1
+	sts.l	pr, @-sp
+	PIC_PROLOGUE(.L_dtor_GOT)
+
+	MOVL_VAR(.L_dtorsp, r0)
+	mov.l	r1, @r0
+
+	mov.l	.L_execsp_main, r0
+1:	CALL	r0
+	 nop
+
+	PIC_EPILOGUE
+	lds.l	@sp+, pr
+	rts
+	 nop
+
+	.p2align 2
+.L_dtor_GOT:	PIC_GOT_DATUM
+.L_dtorsp:	VAR_DATUM(dtorsp)
+.L_execsp_main:	CALL_DATUM(execsp_main, 1b)
+	SET_ENTRY_SIZE(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.pushsection .dtors, "aw", @progbits
+	.p2align 2
+	.long	_C_LABEL(execsp_dtor)
+	.popsection
diff --git a/kernel/arch/sh3/h_execregs.S b/kernel/arch/sh3/h_execregs.S
new file mode 100644
index 000000000000..d7c91161c34a
--- /dev/null
+++ b/kernel/arch/sh3/h_execregs.S
@@ -0,0 +1,86 @@
+/*	$NetBSD: h_execregs.S,v 1.1 2025/04/27 02:24:07 uwe Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+#include <machine/asm.h>
+#include <machine/mcontext.h>
+#include <sys/syscall.h>
+
+
+// ELF entry point
+ENTRY(execregs_start)
+	// __gregset_t r;	// mcontext (but general regs only)
+	mov.l	sp, @-sp
+	mov.l	r0, @-sp
+	mov.l	r1, @-sp
+	mov.l	r2, @-sp
+	mov.l	r3, @-sp
+	mov.l	r4, @-sp
+	mov.l	r5, @-sp
+	mov.l	r6, @-sp
+	mov.l	r7, @-sp
+	mov.l	r8, @-sp
+	mov.l	r9, @-sp
+	mov.l	r10, @-sp
+	mov.l	r11, @-sp
+	mov.l	r12, @-sp
+	mov.l	r13, @-sp
+	mov.l	r14, @-sp
+	sts.l	pr, @-sp
+	sts.l	mach, @-sp
+	sts.l	macl, @-sp
+	mov	#0, r0
+	mov.l	r0, @-sp	// _REG_SR is privileged
+	mova	.Lend, r0	// _REG_PC
+	mov.l	@r0, r1
+	sub	r1, r0
+	mov.l	r0, @-sp
+	stc.l	gbr, @-sp
+
+	// write(STDOUT_FILENO, &r, sizeof(__gregset_t))
+	mov	#1, r4
+	mov	sp, r5
+	mov	#(_NGREG * 4), r6
+	mov	#SYS_write, r0
+	trapa	#0x80
+
+	// _exit(0)
+	mov	#0, r4
+	mov	#SYS_exit, r0
+	trapa	#0x80
+
+	.p2align 2
+.Lend:	.long	.Lend - execregs_start
+	SET_ENTRY_SIZE(execregs_start)
+
+
+// main stub to simplify linking
+ENTRY(main)
+	rts
+	 mov	#0, r0
+	SET_ENTRY_SIZE(main)
diff --git a/kernel/arch/sh3/signalsphandler.S b/kernel/arch/sh3/signalsphandler.S
new file mode 100644
index 000000000000..e0a86ae40558
--- /dev/null
+++ b/kernel/arch/sh3/signalsphandler.S
@@ -0,0 +1,61 @@
+/*	$NetBSD: signalsphandler.S,v 1.2 2025/04/26 23:49:55 uwe Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "asm.h"
+RCSID("$NetBSD: signalsphandler.S,v 1.2 2025/04/26 23:49:55 uwe Exp $")
+
+
+/*
+ * void signalsphandler(int signo)
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+ENTRY(signalsphandler)
+	mov	sp, r1
+#ifdef __PIC__
+	// PR kern/59327: don't touch stack as SP may be misaligned
+	// and as SuperH is a strict alignment architecture, we will
+	// get SIGBUS if we try to save registers on the stack
+	mov	r12, r2
+#endif
+	PIC_PROLOGUE_NOSAVE(.L_GOT)
+
+	MOVL_VAR(.L_signalsp, r0)
+	mov.l	r1, @r0
+
+#ifdef __PIC__
+	mov	r2, r12
+#endif
+	rts
+	 nop
+
+	.p2align 2
+.L_GOT:		PIC_GOT_DATUM
+.L_signalsp:	VAR_DATUM(signalsp)
+	SET_ENTRY_SIZE(signalsphandler)
diff --git a/kernel/arch/sh3/stack_pointer.h b/kernel/arch/sh3/stack_pointer.h
new file mode 100644
index 000000000000..ed3366602f56
--- /dev/null
+++ b/kernel/arch/sh3/stack_pointer.h
@@ -0,0 +1,35 @@
+/*	$NetBSD: stack_pointer.h,v 1.1 2025/04/26 22:34:52 uwe Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_SH3_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_SH3_STACK_POINTER_H
+
+#define MISALIGN_SP	__asm __volatile("add #-1, sp" ::: "memory")
+#define FIX_SP		__asm __volatile("add #+1, sp" ::: "memory")
+
+#endif	/* TESTS_KERNEL_ARCH_SH3_STACK_POINTER_H */
diff --git a/kernel/arch/sh3/threadspfunc.S b/kernel/arch/sh3/threadspfunc.S
new file mode 100644
index 000000000000..de065e54191b
--- /dev/null
+++ b/kernel/arch/sh3/threadspfunc.S
@@ -0,0 +1,41 @@
+/*	$NetBSD: threadspfunc.S,v 1.1 2025/04/26 22:34:52 uwe Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "asm.h"
+RCSID("$NetBSD: threadspfunc.S,v 1.1 2025/04/26 22:34:52 uwe Exp $")
+
+
+/*
+ * void *threadspfunc(void *cookie)
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+ENTRY(threadspfunc)
+	rts
+	 mov	sp, r0
+	SET_ENTRY_SIZE(threadspfunc)
diff --git a/kernel/arch/sparc/contextspfunc.S b/kernel/arch/sparc/contextspfunc.S
new file mode 100644
index 000000000000..a24185cabd73
--- /dev/null
+++ b/kernel/arch/sparc/contextspfunc.S
@@ -0,0 +1,64 @@
+/*	$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:45 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:45 riastradh Exp $")
+
+#ifdef __PIC__
+#define	SETHI(label, got, reg)						      \
+	set	label, reg;		/* reg := &label - &GOT */	      \
+	ld	[got + reg], reg	/* reg := &label */
+#define	LO(label, reg)							      \
+	reg
+#else
+#define	SETHI(label, got, reg)						      \
+	sethi	%hi(label), reg		/* reg := &label - %lo(label) */
+#define	LO(label, reg)							      \
+	reg + %lo(label)
+#endif
+
+	.text
+
+/*
+ * contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+ENTRY(contextspfunc)
+	/* Reminder: o6 is frame pointer, o7 + 8 is return address. */
+	PIC_PROLOGUE(%g1, %o5)			/* g1 := &GOT, clobber o5 */
+	SETHI(_C_LABEL(contextsp), %g1, %o5)	/* o5 := &contextsp */
+	call	_C_LABEL(contextdone)		/* jump to contextdone */
+	 st	%sp, [LO(_C_LABEL(contextsp), %o5)] /* contextsp := sp */
+	/* don't care what happens here, caller must never return */
+	ta	1				/* Tcc, trap always */
+END(contextspfunc)
diff --git a/kernel/arch/sparc/execsp.S b/kernel/arch/sparc/execsp.S
new file mode 100644
index 000000000000..4b225dd6d550
--- /dev/null
+++ b/kernel/arch/sparc/execsp.S
@@ -0,0 +1,123 @@
+/*	$NetBSD: execsp.S,v 1.1 2025/04/20 22:33:41 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: execsp.S,v 1.1 2025/04/20 22:33:41 riastradh Exp $")
+
+#ifdef __PIC__
+#define	SETHI(label, got, reg)						      \
+	set	label, reg;		/* reg := &label - &GOT */	      \
+	ld	[got + reg], reg	/* reg := &label */
+#define	LO(label, reg)							      \
+	reg
+#else
+#define	SETHI(label, got, reg)						      \
+	sethi	%hi(label), reg		/* reg := &label - %lo(label) */
+#define	LO(label, reg)							      \
+	reg + %lo(label)
+#endif
+
+	.text
+
+/*
+ * void execsp_start(struct ps_strings *ps_strings@g1,
+ *     void *obj_main@g2, void (*cleanup@g3)(void))
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ */
+ENTRY(execsp_start)
+	PIC_PROLOGUE(%o1, %o2)			/* o1 := GOT, clobber o2 */
+	SETHI(_C_LABEL(startsp), %o1, %o2)	/* o2 := &startup */
+	call	_C_LABEL(__start)		/* jump to start via PLT */
+	 st	%sp, [LO(_C_LABEL(startsp), %o2)] /* startsp := sp */
+	/* don't care what happens here, caller must never return */
+	ta	1				/* Tcc, trap always */
+END(execsp_start)
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+ENTRY(execsp_ctor)
+	/* Reminder: o6 is frame pointer, o7 + 8 is return address. */
+	PIC_PROLOGUE(%g1, %o5)			/* g1 := &GOT, clobber o5 */
+	SETHI(_C_LABEL(ctorsp), %g1, %o5)	/* o5 := &ctorsp */
+	retl					/* return to caller */
+	 st	%sp, [LO(_C_LABEL(ctorsp), %o5)] /* ctorsp := sp */
+END(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.pushsection .ctors,"aw",@progbits
+	.p2align 2
+	.long	_C_LABEL(execsp_ctor)
+	.popsection
+
+/*
+ * int main(int argc@a0, char **argv@a1, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+ENTRY(main)
+	/* Reminder: o6 is frame pointer, o7 + 8 is return address. */
+	PIC_PROLOGUE(%g1, %o5)			/* g1 := &GOT, clobber o5 */
+	SETHI(_C_LABEL(mainsp), %g1, %o5)	/* o5 := &mainsp */
+	st	%sp, [LO(_C_LABEL(mainsp), %o5)] /* mainsp := sp */
+	retl					/* return to caller */
+	 mov	0, %o0				/* return 0 */
+END(main)
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+ENTRY(execsp_dtor)
+	/* Reminder: o6 is frame pointer, o7 + 8 is return address. */
+	PIC_PROLOGUE(%g1, %o5)			/* g1 := &GOT, clobber o5 */
+	SETHI(_C_LABEL(dtorsp), %g1, %o5)	/* o5 := &dtorsp - &GOT */
+	st	%sp, [LO(_C_LABEL(dtorsp), %o5)] /* dtorsp := sp */
+	mov	%o7, %o5			/* save return address */
+	call	_C_LABEL(execsp_main)		/* tail call to execsp_main */
+	 mov	%o5, %o7			/* restore return address */
+END(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.pushsection .dtors,"aw",@progbits
+	.p2align 2
+	.long	_C_LABEL(execsp_dtor)
+	.popsection
diff --git a/kernel/arch/sparc/signalsphandler.S b/kernel/arch/sparc/signalsphandler.S
new file mode 100644
index 000000000000..187091d23c01
--- /dev/null
+++ b/kernel/arch/sparc/signalsphandler.S
@@ -0,0 +1,62 @@
+/*	$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:33:41 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:33:41 riastradh Exp $")
+
+#ifdef __PIC__
+#define	SETHI(label, got, reg)						      \
+	set	label, reg;		/* reg := &label - &GOT */	      \
+	ld	[got + reg], reg	/* reg := &label */
+#define	LO(label, reg)							      \
+	reg
+#else
+#define	SETHI(label, got, reg)						      \
+	sethi	%hi(label), reg		/* reg := &label - %lo(label) */
+#define	LO(label, reg)							      \
+	reg + %lo(label)
+#endif
+
+	.text
+
+/*
+ * signalsphandler(signo@o0)
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+ENTRY(signalsphandler)
+	/* Reminder: o6 is frame pointer, o7 + 8 is return address. */
+	PIC_PROLOGUE(%g1, %o5)			/* g1 := &GOT, clobber o5 */
+	SETHI(_C_LABEL(signalsp), %g1, %o5)	/* o5 := &signalsp */
+	retl					/* return to caller */
+	 st	%sp, [LO(_C_LABEL(signalsp), %o5)] /* signalsp := sp */
+END(signalsphandler)
diff --git a/kernel/arch/sparc/stack_pointer.h b/kernel/arch/sparc/stack_pointer.h
new file mode 100644
index 000000000000..20c06bec77cd
--- /dev/null
+++ b/kernel/arch/sparc/stack_pointer.h
@@ -0,0 +1,35 @@
+/*	$NetBSD: stack_pointer.h,v 1.1 2025/04/20 22:33:41 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_SPARC_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_SPARC_STACK_POINTER_H
+
+#define MISALIGN_SP	__asm __volatile("dec %%sp" ::: "memory")
+#define FIX_SP		__asm __volatile("inc %%sp" ::: "memory")
+
+#endif	/* TESTS_KERNEL_ARCH_SPARC_STACK_POINTER_H */
diff --git a/kernel/arch/sparc/threadspfunc.S b/kernel/arch/sparc/threadspfunc.S
new file mode 100644
index 000000000000..794804d85741
--- /dev/null
+++ b/kernel/arch/sparc/threadspfunc.S
@@ -0,0 +1,45 @@
+/*	$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:45 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: threadspfunc.S,v 1.1 2025/04/21 02:33:45 riastradh Exp $")
+
+	.text
+
+/*
+ * void *threadspfunc(void *cookie@o0)
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+ENTRY(threadspfunc)
+	retl				/* return to caller */
+	 mov	%sp, %o0		/* return sp */
+END(threadspfunc)
diff --git a/kernel/arch/vax/execregs.c b/kernel/arch/vax/execregs.c
new file mode 100644
index 000000000000..414b810336d8
--- /dev/null
+++ b/kernel/arch/vax/execregs.c
@@ -0,0 +1,166 @@
+/*	$NetBSD: execregs.c,v 1.1 2025/02/27 00:55:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: execregs.c,v 1.1 2025/02/27 00:55:32 riastradh Exp $");
+
+#include "execregs.h"
+
+#include <errno.h>
+#include <spawn.h>
+#include <stddef.h>
+#include <unistd.h>
+
+extern char **environ;
+
+static unsigned long
+nonnull(unsigned long x)
+{
+
+	x |= x << 8;
+	x |= x << 16;
+	return x;
+}
+
+int
+execregschild(char *path)
+{
+	/* fp: frame pointer, nonnull */
+	/* ap: argument pointer, on user stack, nonnull */
+	/* sp: stack pointer, nonnull */
+	register long r0 __asm("r0") = nonnull(0x10);
+	register long r1 __asm("r1") = nonnull(1);
+	register long r2 __asm("r2") = nonnull(2);
+	register long r3 __asm("r3") = nonnull(3);
+	register long r4 __asm("r4") = nonnull(4);
+	register long r5 __asm("r5") = nonnull(5);
+	register long r6 __asm("r6") = nonnull(6);
+	register long r7 __asm("r7") = nonnull(7);
+	register long r8 __asm("r8") = nonnull(8);
+	register long r9 __asm("r9") = nonnull(9);
+	register long r10 __asm("r10") = nonnull(10);
+	register long r11 __asm("r11") = nonnull(11);
+	/* pc: user PC, will be nonnull */
+	/* psl: processor status longword, will be nonnull */
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("" :
+	    "+r"(r0),
+	    "+r"(r1),
+	    "+r"(r2),
+	    "+r"(r3),
+	    "+r"(r4),
+	    "+r"(r5),
+	    "+r"(r6),
+	    "+r"(r7),
+	    "+r"(r8),
+	    "+r"(r9),
+	    "+r"(r10),
+	    "+r"(r11)
+	    :: "memory");
+
+	return execve(path, argv, envp);
+}
+
+pid_t
+spawnregschild(char *path, int fd)
+{
+	/* fp: frame pointer, nonnull */
+	/* ap: argument pointer, on user stack, nonnull */
+	/* sp: stack pointer, nonnull */
+	register long r0 __asm("r0") = nonnull(0x10);
+	register long r1 __asm("r1") = nonnull(1);
+	register long r2 __asm("r2") = nonnull(2);
+	register long r3 __asm("r3") = nonnull(3);
+	register long r4 __asm("r4") = nonnull(4);
+	register long r5 __asm("r5") = nonnull(5);
+	register long r6 __asm("r6") = nonnull(6);
+	register long r7 __asm("r7") = nonnull(7);
+	register long r8 __asm("r8") = nonnull(8);
+	register long r9 __asm("r9") = nonnull(9);
+	register long r10 __asm("r10") = nonnull(10);
+	register long r11 __asm("r11") = nonnull(11);
+	/* pc: user PC, will be nonnull */
+	/* psl: processor status longword, will be nonnull */
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+	posix_spawn_file_actions_t fileacts;
+	posix_spawnattr_t attr;
+	pid_t pid;
+	int error;
+
+	error = posix_spawn_file_actions_init(&fileacts);
+	if (error)
+		goto out;
+	error = posix_spawn_file_actions_adddup2(&fileacts, fd, STDOUT_FILENO);
+	if (error)
+		goto out;
+	error = posix_spawnattr_init(&attr);
+	if (error)
+		goto out;
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("" :
+	    "+r"(r0),
+	    "+r"(r1),
+	    "+r"(r2),
+	    "+r"(r3),
+	    "+r"(r4),
+	    "+r"(r5),
+	    "+r"(r6),
+	    "+r"(r7),
+	    "+r"(r8),
+	    "+r"(r9),
+	    "+r"(r10),
+	    "+r"(r11)
+	    :: "memory");
+
+	error = posix_spawn(&pid, path, &fileacts, &attr, argv, envp);
+	if (error)
+		goto out;
+
+out:	posix_spawnattr_destroy(&attr);
+	posix_spawn_file_actions_destroy(&fileacts);
+	if (error) {
+		errno = error;
+		return -1;
+	}
+	return 0;
+}
diff --git a/kernel/arch/vax/execregs.h b/kernel/arch/vax/execregs.h
new file mode 100644
index 000000000000..882bcd1b6702
--- /dev/null
+++ b/kernel/arch/vax/execregs.h
@@ -0,0 +1,77 @@
+/*	$NetBSD: execregs.h,v 1.1 2025/02/27 00:55:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_VAX_EXECREGS_H
+#define	TESTS_KERNEL_ARCH_VAX_EXECREGS_H
+
+#include <sys/cdefs.h>
+
+#define	NEXECREGS	12
+
+#ifndef _LOCORE
+
+#include <unistd.h>
+
+/*
+ * The order matches that in struct trapframe in
+ * sys/arch/vax/include/trap.h
+ *
+ * Must match h_execregs.S.
+ *
+ * See also sys/arch/vax/vax/trap.c:setregs()
+ */
+static const char *const regname[] = {
+	"fp",	       /* Stack frame pointer */
+	"ap",	       /* Argument pointer on user stack */
+	/* sp: stack pointer */
+	"r0",	       /* General registers saved upon trap/syscall */
+	"r1",
+	"r2",
+	"r3",
+	"r4",
+	"r5",
+	/* r6: initial stack pointer */
+	"r7",
+	"r8",
+	/* r9: ps_strings */
+	"r10",
+	"r11",
+	/* trap: type of trap, not a register */
+	/* code: trap specific code, not a register */
+	/* pc: user PC */
+	/* psl: processor status longword */
+};
+
+__CTASSERT(NEXECREGS == __arraycount(regname));
+
+int	execregschild(char *);
+pid_t	spawnregschild(char *, int);
+
+#endif	/* _LOCORE */
+
+#endif	/* TESTS_KERNEL_ARCH_VAX_EXECREGS_H */
diff --git a/kernel/arch/vax/h_execregs.S b/kernel/arch/vax/h_execregs.S
new file mode 100644
index 000000000000..27c5c2052867
--- /dev/null
+++ b/kernel/arch/vax/h_execregs.S
@@ -0,0 +1,87 @@
+/*	$NetBSD: h_execregs.S,v 1.1 2025/02/27 00:55:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <sys/syscall.h>
+
+#include <machine/asm.h>
+
+#include "execregs.h"
+
+#define REGSIZE 4
+#define BUFSIZE (NEXECREGS * REGSIZE)
+#define SLOT(n)	(n)*REGSIZE(%sp)
+
+ENTRY(execregs_start, 0)
+	/* store registers to a buffer on stack */
+	subl2	$BUFSIZE,%sp		/* space for NEXECREGS registers */
+	movl	%fp,SLOT(0)		/* order matches execregs.h */
+	movl	%ap,SLOT(1)
+	/* sp: stack pointer */
+	movl	%r0,SLOT(2)
+	movl	%r1,SLOT(3)
+	movl	%r2,SLOT(4)
+	movl	%r3,SLOT(5)
+	movl	%r4,SLOT(6)
+	movl	%r5,SLOT(7)
+	/* r6: initial stack pointer */
+	movl	%r7,SLOT(8)
+	movl	%r8,SLOT(9)
+	/* r9: ps_strings */
+	movl	%r10,SLOT(10)
+	movl	%r11,SLOT(11)
+
+	/* call write(STDOUT_FILENO, regs, sizeof(regs)) */
+	pushl	$BUFSIZE		/* arg2 := sizeof(regs) */
+	pushal	4(%sp)			/* arg1 := regs */
+	pushl	$1			/* arg0 := STDOUT_FILENO */
+	pushl	$3			/* number of arguments */
+	movl	%sp,%ap			/* argument pointer */
+	chmk	$SYS_write
+
+	bcs	2f			/* bail if write failed */
+	cmpl	$BUFSIZE,%r0		/* bail if wrote wrong # of bytes */
+	bneq	2f
+
+	/* call exit(0) */
+	pushl	$0			/* arg0 := 0 */
+1:	pushl	$1			/* number of arguments */
+	movl	%sp,%ap			/* argument pointer */
+	chmk	$SYS_exit
+	.word	0xffff			/* paranoia -- illegal opcode */
+
+2:	/* call exit(127) */
+	pushl	$127			/* arg0 := 127 */
+	jmp	1b
+END(execregs_start)
+
+/* main stub to simplify linking */
+ENTRY(main, 0)
+	.word	0xffff			/* illegal opcode */
+END(main)
diff --git a/kernel/arch/x86_64/contextspfunc.S b/kernel/arch/x86_64/contextspfunc.S
new file mode 100644
index 000000000000..d01e1dcdcaf3
--- /dev/null
+++ b/kernel/arch/x86_64/contextspfunc.S
@@ -0,0 +1,55 @@
+/*	$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:45 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: contextspfunc.S,v 1.1 2025/04/21 02:33:45 riastradh Exp $")
+
+/*
+ * contextspfunc()
+ *
+ *	makecontext(3) function.  Store the stack pointer on entry at
+ *	the global variable contextsp and call contextdone.
+ */
+ENTRY(contextspfunc)
+	/*
+	 * `The end of the input argument area shall be aligned on a
+	 *  [16-byte] boundary.  In other words, the value of (%rsp + 8)
+	 *  is always a multiple of 16 when control is transferred to
+	 *  the function entry point.'
+	 *
+	 * To make it convenient for t_signal_and_sp.c, we subtract 8
+	 * from %rsp in order to get something congruent to zero modulo
+	 * the stack alignemnt.
+	 */
+	movq	%rsp,_C_LABEL(contextsp)(%rip)
+	addq	$-8,_C_LABEL(contextsp)(%rip)
+	call	_C_LABEL(contextdone)
+END(contextspfunc)
diff --git a/kernel/arch/x86_64/execregs.c b/kernel/arch/x86_64/execregs.c
new file mode 100644
index 000000000000..fad1b40daa5e
--- /dev/null
+++ b/kernel/arch/x86_64/execregs.c
@@ -0,0 +1,156 @@
+/*	$NetBSD: execregs.c,v 1.1 2025/02/27 00:55:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: execregs.c,v 1.1 2025/02/27 00:55:32 riastradh Exp $");
+
+#include "execregs.h"
+
+#include <errno.h>
+#include <spawn.h>
+#include <stddef.h>
+#include <unistd.h>
+
+extern char **environ;
+
+static unsigned long
+nonnull(unsigned long x)
+{
+
+	x |= x << 8;
+	x |= x << 16;
+	x |= x << 32;
+	return x;
+}
+
+int
+execregschild(char *path)
+{
+	/* rdi: used to pass exec arg0, nonnull anyway (path) */
+	/* rsi: used to pass exec arg1, nonnull anyway (argv) */
+	/* rdx: used to pass exec arg2, nonnull anyway (environ) */
+	register long r10 __asm("r10") = nonnull(10);
+	register long r8 __asm("r8") = nonnull(8);
+	register long r9 __asm("r9") = nonnull(9);
+	register long rcx __asm("rcx") = nonnull('c');
+	register long r11 __asm("r11") = nonnull(11);
+	register long r12 __asm("r12") = nonnull(12);
+	register long r13 __asm("r13") = nonnull(13);
+	register long r14 __asm("r14") = nonnull(14);
+	register long r15 __asm("r15") = nonnull(15);
+	/* rbp: frame pointer, can't touch that here, but it'll be nonnull */
+	/* rbx: ps_strings, passed to child */
+	register long rax __asm("rax") = nonnull('a');
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("" :
+	    "+r"(r10),
+	    "+r"(r8),
+	    "+r"(r9),
+	    "+r"(rcx),
+	    "+r"(r11),
+	    "+r"(r12),
+	    "+r"(r13),
+	    "+r"(r14),
+	    "+r"(r15),
+	    "+r"(rax)
+	    :: "memory");
+
+	return execve(path, argv, envp);
+}
+
+pid_t
+spawnregschild(char *path, int fd)
+{
+	/* rdi: used to pass posix_spawn arg0, nonnull anyway (&pid) */
+	/* rsi: used to pass posix_spawn arg1, nonnull anyway (path) */
+	/* rdx: used to pass posix_spawn arg2, nonnull anyway (&fileacts) */
+	register long r10 __asm("r10") = nonnull(10);
+	/* r8: used to pass posix_spawn arg4, nonnull anyway (argv) */
+	/* r9: used to pass posix_spawn arg5, nonnull anyway (environ) */
+	/* rcx: used to pass posix_spawn arg3, nonnull anyway (&attr) */
+	register long r11 __asm("r11") = nonnull(11);
+	register long r12 __asm("r12") = nonnull(12);
+	register long r13 __asm("r13") = nonnull(13);
+	register long r14 __asm("r14") = nonnull(14);
+	register long r15 __asm("r15") = nonnull(15);
+	/* rbp: frame pointer, can't touch that here, but it'll be nonnull */
+	/* rbx: ps_strings, passed to child */
+	register long rax __asm("rax") = nonnull('a');
+
+	char *argv[] = {path, NULL};
+	char **envp = environ;
+	posix_spawn_file_actions_t fileacts;
+	posix_spawnattr_t attr;
+	pid_t pid;
+	int error;
+
+	error = posix_spawn_file_actions_init(&fileacts);
+	if (error)
+		goto out;
+	error = posix_spawn_file_actions_adddup2(&fileacts, fd, STDOUT_FILENO);
+	if (error)
+		goto out;
+	error = posix_spawnattr_init(&attr);
+	if (error)
+		goto out;
+
+	/*
+	 * Not perfect -- compiler might use some registers for
+	 * stack/argument transfers, but all the arguments are nonnull
+	 * so this is probably a good test anyway.
+	 */
+	__asm volatile("" :
+	    "+r"(r10),
+	    "+r"(r11),
+	    "+r"(r12),
+	    "+r"(r13),
+	    "+r"(r14),
+	    "+r"(r15),
+	    "+r"(rax)
+	    :: "memory");
+
+	error = posix_spawn(&pid, path, &fileacts, &attr, argv, envp);
+	if (error)
+		goto out;
+
+out:	posix_spawnattr_destroy(&attr);
+	posix_spawn_file_actions_destroy(&fileacts);
+	if (error) {
+		errno = error;
+		return -1;
+	}
+	return 0;
+}
diff --git a/kernel/arch/x86_64/execregs.h b/kernel/arch/x86_64/execregs.h
new file mode 100644
index 000000000000..904991777483
--- /dev/null
+++ b/kernel/arch/x86_64/execregs.h
@@ -0,0 +1,81 @@
+/*	$NetBSD: execregs.h,v 1.1 2025/02/27 00:55:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_X86_64_EXECREGS_H
+#define	TESTS_KERNEL_ARCH_X86_64_EXECREGS_H
+
+#include <sys/cdefs.h>
+
+#define	NEXECREGS	14
+
+#ifndef _LOCORE
+
+#include <unistd.h>
+
+/*
+ * Ordered by _FRAME_REG in sys/arch/amd64/include/frame_regs.h for
+ * convenience of auditing.  Must match h_execregs.S.
+ */
+static const char *const regname[] = {
+	"rdi",
+	"rsi",
+	"rdx",
+	"r10",
+	"r8",
+	"r9",
+	/* arg6: syscall arg from stack, not a real register */
+	/* arg7: syscall arg from stack, not a real register */
+	/* arg8: syscall arg from stack, not a real register */
+	/* arg9: syscall arg from stack, not a real register */
+	"rcx",
+	"r11",
+	"r12",
+	"r13",
+	"r14",
+	"r15",
+	"rbp",
+	/* rbx: ps_strings */
+	"rax",
+	/* gs/fs/es/ds: segment registers, not really registers */
+	/* trapno: not a register */
+	/* err: not a register */
+	/* rip: instruction pointer */
+	/* cs: segment register */
+	/* rflags */
+	/* rsp: stack pointer */
+	/* ss: stack selector */
+};
+
+__CTASSERT(NEXECREGS == __arraycount(regname));
+
+int	execregschild(char *);
+pid_t	spawnregschild(char *, int);
+
+#endif	/* _LOCORE */
+
+#endif	/* TESTS_KERNEL_ARCH_X86_64_EXECREGS_H */
diff --git a/kernel/arch/x86_64/execsp.S b/kernel/arch/x86_64/execsp.S
new file mode 100644
index 000000000000..d351dfb2d9e8
--- /dev/null
+++ b/kernel/arch/x86_64/execsp.S
@@ -0,0 +1,111 @@
+/*	$NetBSD: execsp.S,v 1.2 2025/04/20 22:31:25 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: execsp.S,v 1.2 2025/04/20 22:31:25 riastradh Exp $")
+
+/*
+ * void execsp_start(void (*cleanup@rbx)(void), void *obj_main@rcx,
+ *     struct ps_strings *ps_strings@rbx)
+ *
+ *	ELF entry point.  Saves the stack pointer in startsp and defers
+ *	to the usual csu __start routine.
+ */
+ENTRY(execsp_start)
+	movq	%rsp,_C_LABEL(startsp)(%rip)
+	/*
+	 * No adjustment like in main because entry point is special
+	 * and the amd64 csu __start routine takes care of it.
+	 *
+	 * XXX Why don't we just arrange to align it in the kernel
+	 * anyway?
+	 */
+	jmp	_C_LABEL(__start)
+END(execsp_start)
+
+/*
+ * void execsp_ctor(void)
+ *
+ *	ELF constructor.  Saves the stack pointer in ctorsp and
+ *	returns.
+ */
+ENTRY(execsp_ctor)
+	/*
+	 * `The end of the input argument area shall be aligned on a
+	 *  [16-byte] boundary.  In other words, the value of (%rsp + 8)
+	 *  is always a multiple of 16 when control is transferred to
+	 *  the function entry point.'
+	 *
+	 * To make it convenient for t_signal_and_sp.c, we subtract 8
+	 * from %rsp in order to get something congruent to zero modulo
+	 * the stack alignemnt.
+	 */
+	movq	%rsp,_C_LABEL(ctorsp)(%rip)
+	addq	$-8,_C_LABEL(ctorsp)(%rip)
+	ret
+END(execsp_ctor)
+
+	/* Make execsp_ctor a constructor. */
+	.section .ctors,"aw",@progbits
+	.p2align 3
+	.quad	_C_LABEL(execsp_ctor)
+
+/*
+ * int main(int argc@rdi, char **argv@rsi, ...)
+ *
+ *	Main function.  Saves the stack pointer in mainsp and returns
+ *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
+ *	been initialized.
+ */
+ENTRY(main)
+	movq	%rsp,_C_LABEL(mainsp)(%rip)
+	addq	$-8,_C_LABEL(mainsp)(%rip)
+	xorl	%eax,%eax
+	ret
+END(main)
+
+/*
+ * void execsp_dtor(void)
+ *
+ *	ELF destructor.  Saves the stack pointer in dtorsp and defers
+ *	to the C execsp_main in h_execsp.c to report the stack pointers
+ *	back to the t_signal_and_sp parent.
+ */
+ENTRY(execsp_dtor)
+	movq	%rsp,_C_LABEL(dtorsp)(%rip)
+	addq	$-8,_C_LABEL(dtorsp)(%rip)
+	jmp	_C_LABEL(execsp_main)
+END(execsp_dtor)
+
+	/* Make execsp_ctor a destructor. */
+	.section .dtors,"aw",@progbits
+	.p2align 3
+	.quad	_C_LABEL(execsp_dtor)
diff --git a/kernel/arch/x86_64/h_execregs.S b/kernel/arch/x86_64/h_execregs.S
new file mode 100644
index 000000000000..638f73940f06
--- /dev/null
+++ b/kernel/arch/x86_64/h_execregs.S
@@ -0,0 +1,82 @@
+/*	$NetBSD: h_execregs.S,v 1.1 2025/02/27 00:55:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <sys/syscall.h>
+
+#include <machine/asm.h>
+
+#include "execregs.h"
+
+ENTRY(execregs_start)
+	andq	$-0x10,%rsp		/* align stack to 16-byte boundary */
+
+	/* store registers to a buffer on stack */
+	subq	$(NEXECREGS*8),%rsp	/* space for NEXECREGS registers */
+	movq	%rdi,0*8(%rsp)		/* order matches execregs.h */
+	movq	%rsi,1*8(%rsp)
+	movq	%rdx,2*8(%rsp)
+	movq	%r10,3*8(%rsp)
+	movq	%r8,4*8(%rsp)
+	movq	%r9,5*8(%rsp)
+	movq	%rcx,6*8(%rsp)
+	movq	%r11,7*8(%rsp)
+	movq	%r12,8*8(%rsp)
+	movq	%r13,9*8(%rsp)
+	movq	%r14,10*8(%rsp)
+	movq	%r15,11*8(%rsp)
+	movq	%rbp,12*8(%rsp)
+	movq	%rax,13*8(%rsp)
+
+	/* call write(STDOUT_FILENO, regs, sizeof(regs)) */
+	movl	$0x1,%edi		/* arg0 := STDOUT_FILENO */
+	movq	%rsp,%rsi		/* arg1 := regs */
+	movl	$(NEXECREGS*8),%edx	/* arg2 := sizeof(regs) */
+	movl	$SYS_write,%eax		/* syscall number */
+	syscall
+
+	jb	2f			/* bail if write failed */
+	cmpq	$(NEXECREGS*8),%rax	/* bail if wrote wrong # of bytes */
+	jne	2f
+
+	/* call exit(0) */
+	xorl	%edi,%edi		/* arg0 := 0 */
+1:	movl	$SYS_exit,%eax		/* syscall number */
+	syscall
+	hlt				/* paranoia */
+
+2:	/* call exit(127) */
+	movl	$127,%edi		/* arg0 := 127 */
+	jmp	1b
+END(execregs_start)
+
+/* main stub to simplify linking */
+ENTRY(main)
+	hlt
+END(main)
diff --git a/kernel/arch/x86_64/signalsphandler.S b/kernel/arch/x86_64/signalsphandler.S
new file mode 100644
index 000000000000..b53cb005d0b0
--- /dev/null
+++ b/kernel/arch/x86_64/signalsphandler.S
@@ -0,0 +1,55 @@
+/*	$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:31:01 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: signalsphandler.S,v 1.1 2025/04/20 22:31:01 riastradh Exp $")
+
+/*
+ * signalsphandler(signo@rdi)
+ *
+ *	Signal handler.  Store the stack pointer on entry at the global
+ *	variable signalsp and return.
+ */
+ENTRY(signalsphandler)
+	/*
+	 * `The end of the input argument area shall be aligned on a
+	 *  [16-byte] boundary.  In other words, the value of (%rsp + 8)
+	 *  is always a multiple of 16 when control is transferred to
+	 *  the function entry point.'
+	 *
+	 * To make it convenient for t_signal_and_sp.c, we subtract 8
+	 * from %rsp in order to get something congruent to zero modulo
+	 * the stack alignemnt.
+	 */
+	movq	%rsp,_C_LABEL(signalsp)(%rip)
+	addq	$-8,_C_LABEL(signalsp)(%rip)
+	ret
+END(signalsphandler)
diff --git a/kernel/arch/x86_64/stack_pointer.h b/kernel/arch/x86_64/stack_pointer.h
new file mode 100644
index 000000000000..6ea297cf97d9
--- /dev/null
+++ b/kernel/arch/x86_64/stack_pointer.h
@@ -0,0 +1,35 @@
+/*	$NetBSD: stack_pointer.h,v 1.1 2025/04/20 22:31:01 riastradh Exp $	*/
+
+/*
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_ARCH_X86_64_STACK_POINTER_H
+#define	TESTS_KERNEL_ARCH_X86_64_STACK_POINTER_H
+
+#define MISALIGN_SP	__asm __volatile("addq $-1,%rsp")
+#define FIX_SP		__asm __volatile("addq $1,%rsp")
+
+#endif	/* TESTS_KERNEL_ARCH_X86_64_STACK_POINTER_H */
diff --git a/kernel/arch/x86_64/threadspfunc.S b/kernel/arch/x86_64/threadspfunc.S
new file mode 100644
index 000000000000..c939f36b408a
--- /dev/null
+++ b/kernel/arch/x86_64/threadspfunc.S
@@ -0,0 +1,54 @@
+/*	$NetBSD: threadspfunc.S,v 1.2 2025/04/21 12:06:08 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_LOCORE
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: threadspfunc.S,v 1.2 2025/04/21 12:06:08 riastradh Exp $")
+
+/*
+ * void *threadspfunc(void *cookie@rdi)
+ *
+ *	pthread_create(3) function.  Return the stack pointer on entry.
+ */
+ENTRY(threadspfunc)
+	/*
+	 * `The end of the input argument area shall be aligned on a
+	 *  [16-byte] boundary.  In other words, the value of (%rsp + 8)
+	 *  is always a multiple of 16 when control is transferred to
+	 *  the function entry point.'
+	 *
+	 * To make it convenient for t_signal_and_sp.c, we subtract 8
+	 * from %rsp in order to get something congruent to zero modulo
+	 * the stack alignemnt.
+	 */
+	movq	%rsp,%rax
+	addq	$-8,%rax
+	ret
+END(threadspfunc)
diff --git a/kernel/h_cloexec.c b/kernel/h_cloexec.c
new file mode 100644
index 000000000000..55ca4978497f
--- /dev/null
+++ b/kernel/h_cloexec.c
@@ -0,0 +1,48 @@
+/*	$NetBSD: h_cloexec.c,v 1.1 2024/11/10 15:57:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2024 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: h_cloexec.c,v 1.1 2024/11/10 15:57:32 riastradh Exp $");
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int
+main(int argc, char **argv)
+{
+	int fd = atoi(argv[1]);
+	int flags;
+
+	if (fcntl(fd, F_GETFL, &flags) == 0)
+		return 1;
+	if (errno != EBADF)
+		return 2;
+	return 0;
+}
diff --git a/kernel/h_execregs_unimpl.c b/kernel/h_execregs_unimpl.c
new file mode 100644
index 000000000000..606781a2f745
--- /dev/null
+++ b/kernel/h_execregs_unimpl.c
@@ -0,0 +1,37 @@
+/*	$NetBSD: h_execregs_unimpl.c,v 1.1 2025/02/27 00:55:31 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: h_execregs_unimpl.c,v 1.1 2025/02/27 00:55:31 riastradh Exp $");
+
+int
+main(void)
+{
+
+	return 127;
+}
diff --git a/kernel/h_execsp.c b/kernel/h_execsp.c
new file mode 100644
index 000000000000..dac1919e4417
--- /dev/null
+++ b/kernel/h_execsp.c
@@ -0,0 +1,68 @@
+/*	$NetBSD: h_execsp.c,v 1.2 2025/04/20 22:31:25 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: h_execsp.c,v 1.2 2025/04/20 22:31:25 riastradh Exp $");
+
+#include <err.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "h_execsp.h"
+
+/*
+ * The machine-dependent execsp.S assembly routines will initialize
+ * startsp, ctorsp, mainsp, and dtorsp, and then call execsp_main on
+ * program startup.
+ */
+void *startsp;
+void *ctorsp;
+void *mainsp;
+void *dtorsp;
+
+int execsp_main(void);
+int
+execsp_main(void)
+{
+	struct execsp execsp;
+	ssize_t nwrit;
+
+	memset(&execsp, 0, sizeof(execsp));
+	execsp.startsp = startsp;
+	execsp.ctorsp = ctorsp;
+	execsp.mainsp = mainsp;
+	execsp.dtorsp = dtorsp;
+
+	nwrit = write(STDOUT_FILENO, &execsp, sizeof(execsp));
+	if (nwrit == -1)
+		err(1, "write");
+	if ((size_t)nwrit != sizeof(execsp))
+		errx(1, "wrote %zu != %zu", (size_t)nwrit, sizeof(execsp));
+
+	return 0;
+}
diff --git a/kernel/h_execsp.h b/kernel/h_execsp.h
new file mode 100644
index 000000000000..e94ceaab9c1b
--- /dev/null
+++ b/kernel/h_execsp.h
@@ -0,0 +1,47 @@
+/*	$NetBSD: h_execsp.h,v 1.2 2025/04/20 22:31:25 riastradh Exp $	*/
+
+/*
+ * Copyright (c) 2024 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	TESTS_KERNEL_H_EXECSP_H
+#define	TESTS_KERNEL_H_EXECSP_H
+
+/*
+ * struct execsp
+ *
+ *	Structure passed from the h_execsp_* programs to the
+ *	t_signal_and_sp test, giving the stack pointer as it was at the
+ *	ELF entry point, an ELF constructor, the main function, and an
+ *	ELF destructor.
+ */
+struct execsp {
+	void	*startsp;
+	void	*ctorsp;
+	void	*mainsp;
+	void	*dtorsp;
+};
+
+#endif	/* TESTS_KERNEL_H_EXECSP_H */
diff --git a/kernel/setjmp_tester/Makefile b/kernel/setjmp_tester/Makefile
new file mode 100644
index 000000000000..18492f35fd4a
--- /dev/null
+++ b/kernel/setjmp_tester/Makefile
@@ -0,0 +1,12 @@
+#	$NetBSD: Makefile,v 1.1 2025/04/27 16:22:26 riastradh Exp $
+
+KMOD=		setjmp_tester
+KMODULEDIR=	${TESTSBASE}/kernel/${KMOD}
+
+SRCS=		setjmp_tester.c
+
+ATFFILE=	no
+NOMAN=		# defined
+
+.include <bsd.test.mk>
+.include <bsd.kmodule.mk>
diff --git a/kernel/setjmp_tester/setjmp_tester.c b/kernel/setjmp_tester/setjmp_tester.c
new file mode 100644
index 000000000000..8b15b840effe
--- /dev/null
+++ b/kernel/setjmp_tester/setjmp_tester.c
@@ -0,0 +1,147 @@
+/*	$NetBSD: setjmp_tester.c,v 1.1 2025/04/27 16:22:26 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__KERNEL_RCSID(0, "$NetBSD: setjmp_tester.c,v 1.1 2025/04/27 16:22:26 riastradh Exp $");
+
+#include <sys/module.h>
+#include <sys/sysctl.h>
+#include <sys/systm.h>
+
+MODULE(MODULE_CLASS_MISC, setjmp_tester, NULL);
+
+static struct sysctllog *setjmp_tester_sysctllog;
+static const struct sysctlnode *setjmp_tester_sysctlnode;
+static kmutex_t setjmp_tester_lock;
+static bool setjmp_tester_done;
+static label_t setjmp_tester_label;
+
+__noinline
+static void
+setjmp_tester_subroutine(void)
+{
+
+	printf("%s: call longjmp\n", __func__);
+	setjmp_tester_done = true;
+	longjmp(&setjmp_tester_label);
+	printf("%s: unreachable\n", __func__);
+}
+
+static int
+setjmp_tester_test(void)
+{
+	int result;
+
+	mutex_enter(&setjmp_tester_lock);
+
+	setjmp_tester_done = false;
+	result = setjmp(&setjmp_tester_label);
+	if (!setjmp_tester_done) {
+		printf("%s: setjmp returned %d at first\n", __func__, result);
+		if (result != 0) {
+			result = -1;
+			goto out;
+		}
+		setjmp_tester_subroutine();
+		/*NOTREACHED*/
+		printf("%s: setjmp_tester_subroutine returned\n", __func__);
+		result = -1;
+	} else {
+		printf("%s: setjmp returned %d at second\n", __func__, result);
+		if (result == 0) {
+			result = -2;
+			goto out;
+		}
+	}
+
+out:	mutex_exit(&setjmp_tester_lock);
+	return result;
+}
+
+static int
+setjmp_tester_test_sysctl(SYSCTLFN_ARGS)
+{
+	struct sysctlnode node = *rnode;
+	int v = 0;
+	int error;
+
+	if (newp == NULL) {
+		error = ENOENT;
+		goto out;
+	}
+	error = sysctl_copyin(curlwp, newp, &v, sizeof(v));
+	if (error)
+		goto out;
+	switch (v) {
+	case 1:
+		v = setjmp_tester_test();
+		break;
+	default:
+		error = EINVAL;
+		break;
+	}
+	node.sysctl_data = &v;
+	error = sysctl_lookup(SYSCTLFN_CALL(&node));
+
+out:	return error;
+}
+
+static int
+setjmp_tester_modcmd(modcmd_t cmd, void *arg)
+{
+	int error = 0;
+
+	switch (cmd) {
+	case MODULE_CMD_INIT:
+		mutex_init(&setjmp_tester_lock, MUTEX_DEFAULT, IPL_NONE);
+		error = sysctl_createv(&setjmp_tester_sysctllog, 0,
+		    NULL, &setjmp_tester_sysctlnode,
+		    CTLFLAG_PERMANENT, CTLTYPE_NODE, "setjmp_tester",
+		    SYSCTL_DESCR("setjmp/longjmp testing interface"),
+		    NULL, 0, NULL, 0,
+		    CTL_KERN, CTL_CREATE, CTL_EOL);
+		if (error)
+			goto fini;
+		error = sysctl_createv(&setjmp_tester_sysctllog, 0,
+		    &setjmp_tester_sysctlnode, NULL,
+		    CTLFLAG_PERMANENT|CTLFLAG_READWRITE, CTLTYPE_INT, "test",
+		    SYSCTL_DESCR("setjmp/longjmp test trigger"),
+		    &setjmp_tester_test_sysctl, 0, NULL, 0,
+		    CTL_CREATE, CTL_EOL);
+		if (error)
+			goto fini;
+		return error;
+	case MODULE_CMD_FINI:
+	fini:
+		sysctl_teardown(&setjmp_tester_sysctllog);
+		mutex_destroy(&setjmp_tester_lock);
+		return error;
+	default:
+		return ENOTTY;
+	}
+}
diff --git a/kernel/t_cloexec.c b/kernel/t_cloexec.c
new file mode 100644
index 000000000000..c0150af8ca38
--- /dev/null
+++ b/kernel/t_cloexec.c
@@ -0,0 +1,457 @@
+/*	$NetBSD: t_cloexec.c,v 1.1 2024/11/10 15:57:32 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2024 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: t_cloexec.c,v 1.1 2024/11/10 15:57:32 riastradh Exp $");
+
+#include <sys/types.h>
+
+#include <sys/bitops.h>
+#include <sys/event.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+
+#include <atf-c.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <spawn.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "h_macros.h"
+
+/*
+ * Test close-on-exec as set in various ways
+ */
+
+static int
+open_via_accept4(void)
+{
+	static const union {
+		struct sockaddr sa;
+		struct sockaddr_un sun;
+	} name = { .sun = {
+		.sun_family = AF_LOCAL,
+		.sun_path = "socket",
+	} };
+	int slisten, saccept, c;
+
+	/*
+	 * Create a listening server socket and bind it to the path.
+	 */
+	RL(slisten = socket(PF_LOCAL, SOCK_STREAM, 0));
+	RL(bind(slisten, &name.sa, sizeof(name)));
+	RL(listen(slisten, SOMAXCONN));
+
+	/*
+	 * Create an active client socket and connect it to the path --
+	 * nonblocking, so we don't deadlock here.  If connect doesn't
+	 * succeed immediately, it had better fail immediately with
+	 * EINPROGRESS.
+	 */
+	RL(c = socket(PF_LOCAL, SOCK_STREAM|SOCK_NONBLOCK, 0));
+	if (connect(c, &name.sa, sizeof(name)) == -1) {
+		ATF_CHECK_EQ_MSG(errno, EINPROGRESS, "connect failed %d: %s",
+		    errno, strerror(errno));
+	}
+
+	/*
+	 * Accept a socket on the server side with SOCK_CLOEXEC.
+	 */
+	RL(saccept = accept4(slisten, /*addr*/NULL, /*addrlen*/NULL,
+		SOCK_CLOEXEC));
+	return saccept;
+}
+
+static int
+open_via_clonedev(void)
+{
+	int fd;
+
+	RL(fd = open("/dev/drvctl", O_RDONLY|O_CLOEXEC));
+
+	return fd;
+}
+
+static int
+open_via_dup3(void)
+{
+	int fd3;
+
+	RL(fd3 = dup3(STDIN_FILENO, 3, O_CLOEXEC));
+	ATF_REQUIRE_EQ_MSG(fd3, 3, "dup3(STDIN_FILENO, 3, ...)"
+	    " failed to return 3: %d", fd3);
+
+	return fd3;
+}
+
+static int
+open_via_fcntldupfd(void)
+{
+	int fd;
+
+	RL(fd = fcntl(STDIN_FILENO, F_DUPFD_CLOEXEC, 0));
+
+	return fd;
+}
+
+static int
+open_via_kqueue(void)
+{
+	int fd;
+
+	RL(fd = kqueue1(O_CLOEXEC));
+
+	return fd;
+}
+
+static int
+open_via_opencloexec(void)
+{
+	int fd;
+
+	RL(fd = open("file", O_RDWR|O_CREAT|O_CLOEXEC, 0644));
+
+	return fd;
+}
+
+static int
+open_via_openfcntlcloexec(void)
+{
+	int fd;
+
+	RL(fd = open("file", O_RDWR|O_CREAT, 0644));
+	RL(fcntl(fd, F_SETFD, FD_CLOEXEC));
+
+	return fd;
+}
+
+static int
+open_via_openioctlfioclex(void)
+{
+	int fd;
+
+	RL(fd = open("file", O_RDWR|O_CREAT, 0644));
+	RL(ioctl(fd, FIOCLEX));
+
+	return fd;
+}
+
+static int
+open_via_pipe2rd(void)
+{
+	int fd[2];
+
+	RL(pipe2(fd, O_CLOEXEC));
+
+	return fd[0];
+}
+
+static int
+open_via_pipe2wr(void)
+{
+	int fd[2];
+
+	RL(pipe2(fd, O_CLOEXEC));
+
+	return fd[1];
+}
+
+static int
+open_via_paccept(void)
+{
+	static const union {
+		struct sockaddr sa;
+		struct sockaddr_un sun;
+	} name = { .sun = {
+		.sun_family = AF_LOCAL,
+		.sun_path = "socket",
+	} };
+	int slisten, saccept, c;
+
+	/*
+	 * Create a listening server socket and bind it to the path.
+	 */
+	RL(slisten = socket(PF_LOCAL, SOCK_STREAM, 0));
+	RL(bind(slisten, &name.sa, sizeof(name)));
+	RL(listen(slisten, SOMAXCONN));
+
+	/*
+	 * Create an active client socket and connect it to the path --
+	 * nonblocking, so we don't deadlock here.  If connect doesn't
+	 * succeed immediately, it had better fail immediately with
+	 * EINPROGRESS.
+	 */
+	RL(c = socket(PF_LOCAL, SOCK_STREAM|SOCK_NONBLOCK, 0));
+	if (connect(c, &name.sa, sizeof(name)) == -1) {
+		ATF_CHECK_EQ_MSG(errno, EINPROGRESS, "connect failed %d: %s",
+		    errno, strerror(errno));
+	}
+
+	/*
+	 * Accept a socket on the server side with SOCK_CLOEXEC.
+	 */
+	RL(saccept = paccept(slisten, /*addr*/NULL, /*addrlen*/NULL,
+		/*sigmask*/NULL, SOCK_CLOEXEC));
+	return saccept;
+}
+
+static int
+open_via_socket(void)
+{
+	int fd;
+
+	RL(fd = socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC, 0));
+
+	return fd;
+}
+
+static int
+open_via_socketpair0(void)
+{
+	int fd[2];
+
+	RL(socketpair(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC, 0, fd));
+
+	return fd[0];
+}
+
+static int
+open_via_socketpair1(void)
+{
+	int fd[2];
+
+	RL(socketpair(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC, 0, fd));
+
+	return fd[1];
+}
+
+/*
+ * XXX Close-on-exec paths still missing:
+ * XXX
+ * XXX compat_linux inotify
+ * XXX compat_linux close_range
+ * XXX drm i915_perf_open_ioctl
+ * XXX drm dma_buf
+ * XXX eventfd(2)
+ * XXX memfd(2)
+ * XXX timerfd(2)
+ * XXX recvmsg/recvmmsg with MSG_CMSG_CLOEXEC
+ */
+
+static void
+check_cloexec(const struct atf_tc *tc, int fd,
+    pid_t (*execfn)(char *, char *const[]))
+{
+	char h_cloexec[PATH_MAX];
+	char fdstr[(ilog2(INT_MAX) + 1)/(ilog2(10) - 1) + 1];
+	char *const argv[] = {__UNCONST("h_cloexec"), fdstr, NULL};
+	pid_t child, waitedpid;
+	int status;
+
+	/*
+	 * Format the h_cloexec helper executable path, which lives in
+	 * the test's directory (typically /usr/tests/kernel), and the
+	 * argument of a file descriptor in decimal.
+	 */
+	snprintf(h_cloexec, sizeof(h_cloexec), "%s/h_cloexec",
+	    atf_tc_get_config_var(tc, "srcdir"));
+	snprintf(fdstr, sizeof(fdstr), "%d", fd);
+
+	/*
+	 * Execute h_cloexec as a subprocess.
+	 */
+	child = (*execfn)(h_cloexec, argv);
+
+	/*
+	 * Wait for the child to complete.
+	 */
+	RL(waitedpid = waitpid(child, &status, 0));
+	ATF_CHECK_EQ_MSG(child, waitedpid, "waited for %jd, got %jd",
+	    (intmax_t)child, (intmax_t)waitedpid);
+
+	/*
+	 * Verify the child exited normally.
+	 */
+	if (WIFSIGNALED(status)) {
+		atf_tc_fail("subprocess terminated on signal %d",
+		    WTERMSIG(status));
+		return;
+	} else if (!WIFEXITED(status)) {
+		atf_tc_fail("subprocess failed to exit normally: status=0x%x",
+		    status);
+		return;
+	}
+
+	/*
+	 * h_cloexec is supposed to exit status 0 if an operation on
+	 * the fd failed with EBADFD, 1 if it unexpectedly succeeded,
+	 * 127 if exec returned, or something else if anything else
+	 * happened.
+	 */
+	switch (WEXITSTATUS(status)) {
+	case 0:			/* success -- closed on exec */
+		return;
+	case 1:			/* fail -- not closed on exec */
+		atf_tc_fail("fd was not closed on exec");
+		return;
+	case 127:		/* exec failed */
+		atf_tc_fail("failed to exec h_cloexec");
+		return;
+	default:		/* something else went wong */
+		atf_tc_fail("h_cloexec failed unexpectedly: %d",
+		    WEXITSTATUS(status));
+		return;
+	}
+}
+
+static pid_t
+exec_via_forkexecve(char *prog, char *const argv[])
+{
+	pid_t pid;
+
+	RL(pid = fork());
+	if (pid == 0) {		/* child */
+		if (execve(prog, argv, /*envp*/NULL) == -1)
+			_exit(127);
+		abort();
+	}
+
+	/* parent */
+	return pid;
+}
+
+static pid_t
+exec_via_vforkexecve(char *prog, char *const argv[])
+{
+	pid_t pid;
+
+	RL(pid = vfork());
+	if (pid == 0) {		/* child */
+		if (execve(prog, argv, /*envp*/NULL) == -1)
+			_exit(127);
+		abort();
+	}
+
+	/* parent */
+	return pid;
+}
+
+static pid_t
+exec_via_posixspawn(char *prog, char *const argv[])
+{
+	pid_t pid;
+
+	RZ(posix_spawn(&pid, prog, /*file_actions*/NULL, /*attrp*/NULL, argv,
+		/*envp*/NULL));
+
+	return pid;
+}
+
+/*
+ * Full cartesian product is not really important here -- the paths for
+ * open and the paths for exec are independent.  So we try
+ * pipe2(O_CLOEXEC) with each exec path, and we try each open path with
+ * posix_spawn.
+ */
+
+#define	CLOEXEC_TEST(test, openvia, execvia, descr)			      \
+ATF_TC(test);								      \
+ATF_TC_HEAD(test, tc)							      \
+{									      \
+	atf_tc_set_md_var(tc, "descr", descr);				      \
+}									      \
+ATF_TC_BODY(test, tc)							      \
+{									      \
+	check_cloexec(tc, openvia(), &execvia);				      \
+}
+
+CLOEXEC_TEST(pipe2rd_forkexecve, open_via_pipe2rd, exec_via_forkexecve,
+    "pipe2(O_CLOEXEC) reader is closed in child on fork/exec")
+CLOEXEC_TEST(pipe2rd_vforkexecve, open_via_pipe2rd, exec_via_vforkexecve,
+    "pipe2(O_CLOEXEC) reader is closed in child on vfork/exec")
+CLOEXEC_TEST(pipe2rd_posixspawn, open_via_pipe2rd, exec_via_posixspawn,
+    "pipe2(O_CLOEXEC) reader is closed in child on posix_spawn")
+
+CLOEXEC_TEST(accept4_posixspawn, open_via_accept4, exec_via_posixspawn,
+    "accept4(SOCK_CLOEXEC) is closed in child on posix_spawn");
+CLOEXEC_TEST(clonedev_posixspawn, open_via_clonedev, exec_via_posixspawn,
+    "open(\"/dev/drvctl\") is closed in child on posix_spawn");
+CLOEXEC_TEST(dup3_posixspawn, open_via_dup3, exec_via_posixspawn,
+    "dup3(..., O_CLOEXEC) is closed in child on posix_spawn");
+CLOEXEC_TEST(fcntldupfd_posixspawn, open_via_fcntldupfd, exec_via_posixspawn,
+    "fcntl(STDIN_FILENO, F_DUPFD_CLOEXEC) is closed in child on posix_spawn");
+CLOEXEC_TEST(kqueue_posixspawn, open_via_kqueue, exec_via_posixspawn,
+    "kqueue1(O_CLOEXEC) is closed in child on posix_spawn");
+CLOEXEC_TEST(opencloexec_posixspawn, open_via_opencloexec, exec_via_posixspawn,
+    "open(O_CLOEXEC) is closed in child on posix_spawn");
+CLOEXEC_TEST(openfcntlcloexec_posixspawn, open_via_openfcntlcloexec,
+    exec_via_posixspawn,
+    "fcntl(open(...), F_SETFD, O_CLOEXEC) is closed in child on posix_spawn");
+CLOEXEC_TEST(openioctlfioclex_posixspawn, open_via_openioctlfioclex,
+    exec_via_posixspawn,
+    "ioctl(open(...), FIOCLEX) is closed in child on posix_spawn");
+#if 0				/* already done above */
+CLOEXEC_TEST(pipe2rd_posixspawn, open_via_pipe2rd, exec_via_posixspawn,
+    "pipe2(O_CLOEXEC) reader is closed in child on posix_spawn")
+#endif
+CLOEXEC_TEST(pipe2wr_posixspawn, open_via_pipe2wr, exec_via_posixspawn,
+    "pipe2(O_CLOEXEC) writer is closed in child on posix_spawn")
+CLOEXEC_TEST(paccept_posixspawn, open_via_paccept, exec_via_posixspawn,
+    "paccept(..., SOCK_CLOEXEC) is closed in child on posix_spawn")
+CLOEXEC_TEST(socket_posixspawn, open_via_socket, exec_via_posixspawn,
+    "socket(SOCK_CLOEXEC) is closed in child on posix_spawn")
+CLOEXEC_TEST(socketpair0_posixspawn, open_via_socketpair0, exec_via_posixspawn,
+    "socketpair(SOCK_CLOEXEC) side 0 is closed in child on posix_spawn")
+CLOEXEC_TEST(socketpair1_posixspawn, open_via_socketpair1, exec_via_posixspawn,
+    "socketpair(SOCK_CLOEXEC) side 1 is closed in child on posix_spawn")
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, accept4_posixspawn);
+	ATF_TP_ADD_TC(tp, clonedev_posixspawn);
+	ATF_TP_ADD_TC(tp, dup3_posixspawn);
+	ATF_TP_ADD_TC(tp, fcntldupfd_posixspawn);
+	ATF_TP_ADD_TC(tp, kqueue_posixspawn);
+	ATF_TP_ADD_TC(tp, opencloexec_posixspawn);
+	ATF_TP_ADD_TC(tp, openfcntlcloexec_posixspawn);
+	ATF_TP_ADD_TC(tp, openioctlfioclex_posixspawn);
+	ATF_TP_ADD_TC(tp, paccept_posixspawn);
+	ATF_TP_ADD_TC(tp, pipe2rd_forkexecve);
+	ATF_TP_ADD_TC(tp, pipe2rd_posixspawn);
+	ATF_TP_ADD_TC(tp, pipe2rd_vforkexecve);
+	ATF_TP_ADD_TC(tp, pipe2wr_posixspawn);
+	ATF_TP_ADD_TC(tp, socket_posixspawn);
+	ATF_TP_ADD_TC(tp, socketpair0_posixspawn);
+	ATF_TP_ADD_TC(tp, socketpair1_posixspawn);
+
+	return atf_no_error();
+}
diff --git a/kernel/t_clofork.c b/kernel/t_clofork.c
new file mode 100644
index 000000000000..9c1ba81c733a
--- /dev/null
+++ b/kernel/t_clofork.c
@@ -0,0 +1,445 @@
+/*	$NetBSD: t_clofork.c,v 1.1 2025/07/17 19:50:40 kre Exp $	*/
+
+/*-
+ * Copyright (c) 2024 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* Adapted from t_cloexec.c */
+
+#include <sys/cdefs.h>
+
+#include <sys/types.h>
+
+#include <sys/bitops.h>
+#include <sys/event.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+
+#include <atf-c.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <spawn.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "h_macros.h"
+
+#if defined(O_CLOFORK) && O_CLOFORK != 0
+/*
+ * Test close-on-fork as set in various ways
+ */
+
+static int
+open_via_accept4(void)
+{
+	static const union {
+		struct sockaddr sa;
+		struct sockaddr_un sun;
+	} name = { .sun = {
+		.sun_family = AF_LOCAL,
+		.sun_path = "socket",
+	} };
+	int slisten, saccept, c;
+
+	/*
+	 * Create a listening server socket and bind it to the path.
+	 */
+	RL(slisten = socket(PF_LOCAL, SOCK_STREAM, 0));
+	RL(bind(slisten, &name.sa, sizeof(name)));
+	RL(listen(slisten, SOMAXCONN));
+
+	/*
+	 * Create an active client socket and connect it to the path --
+	 * nonblocking, so we don't deadlock here.  If connect doesn't
+	 * succeed immediately, it had better fail immediately with
+	 * EINPROGRESS.
+	 */
+	RL(c = socket(PF_LOCAL, SOCK_STREAM|SOCK_NONBLOCK, 0));
+	if (connect(c, &name.sa, sizeof(name)) == -1) {
+		ATF_CHECK_EQ_MSG(errno, EINPROGRESS, "connect failed %d: %s",
+		    errno, strerror(errno));
+	}
+
+	/*
+	 * Accept a socket on the server side with SOCK_CLOFORK.
+	 */
+	RL(saccept = accept4(slisten, /*addr*/NULL, /*addrlen*/NULL,
+		SOCK_CLOFORK));
+	return saccept;
+}
+
+static int
+open_via_clonedev(void)
+{
+	int fd;
+
+	RL(fd = open("/dev/drvctl", O_RDONLY|O_CLOFORK));
+
+	return fd;
+}
+
+static int
+open_via_dup3(void)
+{
+	int fd3;
+
+	RL(fd3 = dup3(STDIN_FILENO, 3, O_CLOFORK));
+	ATF_REQUIRE_EQ_MSG(fd3, 3, "dup3(STDIN_FILENO, 3, ...)"
+	    " failed to return 3: %d", fd3);
+
+	return fd3;
+}
+
+static int
+open_via_fcntldupfd(void)
+{
+	int fd;
+
+	RL(fd = fcntl(STDIN_FILENO, F_DUPFD_CLOFORK, 0));
+
+	return fd;
+}
+
+static int
+open_via_kqueue(void)
+{
+	int fd;
+
+	RL(fd = kqueue1(O_CLOFORK));
+
+	return fd;
+}
+
+static int
+open_via_openclofork(void)
+{
+	int fd;
+
+	RL(fd = open("file", O_RDWR|O_CREAT|O_CLOFORK, 0644));
+
+	return fd;
+}
+
+static int
+open_via_openfcntlclofork(void)
+{
+	int fd;
+
+	RL(fd = open("file", O_RDWR|O_CREAT, 0644));
+	RL(fcntl(fd, F_SETFD, FD_CLOFORK));
+
+	return fd;
+}
+
+static int
+open_via_pipe2rd(void)
+{
+	int fd[2];
+
+	RL(pipe2(fd, O_CLOFORK));
+
+	return fd[0];
+}
+
+static int
+open_via_pipe2wr(void)
+{
+	int fd[2];
+
+	RL(pipe2(fd, O_CLOFORK));
+
+	return fd[1];
+}
+
+static int
+open_via_paccept(void)
+{
+	static const union {
+		struct sockaddr sa;
+		struct sockaddr_un sun;
+	} name = { .sun = {
+		.sun_family = AF_LOCAL,
+		.sun_path = "socket",
+	} };
+	int slisten, saccept, c;
+
+	/*
+	 * Create a listening server socket and bind it to the path.
+	 */
+	RL(slisten = socket(PF_LOCAL, SOCK_STREAM, 0));
+	RL(bind(slisten, &name.sa, sizeof(name)));
+	RL(listen(slisten, SOMAXCONN));
+
+	/*
+	 * Create an active client socket and connect it to the path --
+	 * nonblocking, so we don't deadlock here.  If connect doesn't
+	 * succeed immediately, it had better fail immediately with
+	 * EINPROGRESS.
+	 */
+	RL(c = socket(PF_LOCAL, SOCK_STREAM|SOCK_NONBLOCK, 0));
+	if (connect(c, &name.sa, sizeof(name)) == -1) {
+		ATF_CHECK_EQ_MSG(errno, EINPROGRESS, "connect failed %d: %s",
+		    errno, strerror(errno));
+	}
+
+	/*
+	 * Accept a socket on the server side with SOCK_CLOFORK.
+	 */
+	RL(saccept = paccept(slisten, /*addr*/NULL, /*addrlen*/NULL,
+		/*sigmask*/NULL, SOCK_CLOFORK));
+	return saccept;
+}
+
+static int
+open_via_socket(void)
+{
+	int fd;
+
+	RL(fd = socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOFORK, 0));
+
+	return fd;
+}
+
+static int
+open_via_socketpair0(void)
+{
+	int fd[2];
+
+	RL(socketpair(PF_LOCAL, SOCK_STREAM|SOCK_CLOFORK, 0, fd));
+
+	return fd[0];
+}
+
+static int
+open_via_socketpair1(void)
+{
+	int fd[2];
+
+	RL(socketpair(PF_LOCAL, SOCK_STREAM|SOCK_CLOFORK, 0, fd));
+
+	return fd[1];
+}
+
+static void
+check_clofork(const struct atf_tc *tc, int fd,
+    pid_t (*execfn)(char *, char *const[]))
+{
+	char h_clofork[PATH_MAX];
+	char fdstr[(ilog2(INT_MAX) + 1)/(ilog2(10) - 1) + 1];
+	char *const argv[] = {__UNCONST("h_cloexec"), fdstr, NULL};
+	pid_t child, waitedpid;
+	int status;
+
+	/*
+	 * Format the h_clofork helper executable path, which lives in
+	 * the test's directory (typically /usr/tests/kernel), and the
+	 * argument of a file descriptor in decimal.
+	 */
+	snprintf(h_clofork, sizeof(h_clofork), "%s/h_cloexec",
+	    atf_tc_get_config_var(tc, "srcdir"));
+	snprintf(fdstr, sizeof(fdstr), "%d", fd);
+
+	/*
+	 * Execute h_clofork as a subprocess.
+	 */
+	child = (*execfn)(h_clofork, argv);
+
+	/*
+	 * Wait for the child to complete.
+	 */
+	RL(waitedpid = waitpid(child, &status, 0));
+	ATF_CHECK_EQ_MSG(child, waitedpid, "waited for %jd, got %jd",
+	    (intmax_t)child, (intmax_t)waitedpid);
+
+	/*
+	 * Verify the child exited normally.
+	 */
+	if (WIFSIGNALED(status)) {
+		atf_tc_fail("subprocess terminated on signal %d",
+		    WTERMSIG(status));
+		return;
+	} else if (!WIFEXITED(status)) {
+		atf_tc_fail("subprocess failed to exit normally: status=0x%x",
+		    status);
+		return;
+	}
+
+	/*
+	 * h_clofork is supposed to exit status 0 if an operation on
+	 * the fd failed with EBADFD, 1 if it unexpectedly succeeded,
+	 * 127 if exec returned, or something else if anything else
+	 * happened.
+	 */
+	switch (WEXITSTATUS(status)) {
+	case 0:			/* success -- closed on exec */
+		return;
+	case 1:			/* fail -- not closed on exec */
+		atf_tc_fail("fd was not closed on exec");
+		return;
+	case 127:		/* exec failed */
+		atf_tc_fail("failed to exec h_cloexec");
+		return;
+	default:		/* something else went wong */
+		atf_tc_fail("h_cloexec failed unexpectedly: %d",
+		    WEXITSTATUS(status));
+		return;
+	}
+}
+
+static pid_t
+exec_via_forkexecve(char *prog, char *const argv[])
+{
+	pid_t pid;
+
+	RL(pid = fork());
+	if (pid == 0) {		/* child */
+		if (execve(prog, argv, /*envp*/NULL) == -1)
+			_exit(127);
+		abort();
+	}
+
+	/* parent */
+	return pid;
+}
+
+static pid_t
+exec_via_vforkexecve(char *prog, char *const argv[])
+{
+	pid_t pid;
+
+	RL(pid = vfork());
+	if (pid == 0) {		/* child */
+		if (execve(prog, argv, /*envp*/NULL) == -1)
+			_exit(127);
+		abort();
+	}
+
+	/* parent */
+	return pid;
+}
+
+static pid_t
+exec_via_posixspawn(char *prog, char *const argv[])
+{
+	pid_t pid;
+
+	RZ(posix_spawn(&pid, prog, /*file_actions*/NULL, /*attrp*/NULL, argv,
+		/*envp*/NULL));
+
+	return pid;
+}
+
+/*
+ * Full cartesian product is not really important here -- the paths for
+ * open and the paths for exec are independent.  So we try
+ * pipe2(O_CLOFORK) with each exec path, and we try each open path with
+ * posix_spawn.
+ */
+
+#define	CLOFORK_TEST(test, openvia, execvia, descr)			      \
+ATF_TC(test);								      \
+ATF_TC_HEAD(test, tc)							      \
+{									      \
+	atf_tc_set_md_var(tc, "descr", descr);				      \
+}									      \
+ATF_TC_BODY(test, tc)							      \
+{									      \
+	check_clofork(tc, openvia(), &execvia);				      \
+}
+
+CLOFORK_TEST(pipe2rd_forkexecve, open_via_pipe2rd, exec_via_forkexecve,
+    "pipe2(O_CLOFORK) reader is closed in child on fork/exec")
+CLOFORK_TEST(pipe2rd_vforkexecve, open_via_pipe2rd, exec_via_vforkexecve,
+    "pipe2(O_CLOFORK) reader is closed in child on vfork/exec")
+CLOFORK_TEST(pipe2rd_posixspawn, open_via_pipe2rd, exec_via_posixspawn,
+    "pipe2(O_CLOFORK) reader is closed in child on posix_spawn")
+
+CLOFORK_TEST(accept4_posixspawn, open_via_accept4, exec_via_posixspawn,
+    "accept4(SOCK_CLOFORK) is closed in child on posix_spawn");
+CLOFORK_TEST(clonedev_posixspawn, open_via_clonedev, exec_via_posixspawn,
+    "open(\"/dev/drvctl\") is closed in child on posix_spawn");
+CLOFORK_TEST(dup3_posixspawn, open_via_dup3, exec_via_posixspawn,
+    "dup3(..., O_CLOFORK) is closed in child on posix_spawn");
+CLOFORK_TEST(fcntldupfd_posixspawn, open_via_fcntldupfd, exec_via_posixspawn,
+    "fcntl(STDIN_FILENO, F_DUPFD_CLOFORK) is closed in child on posix_spawn");
+CLOFORK_TEST(kqueue_posixspawn, open_via_kqueue, exec_via_posixspawn,
+    "kqueue1(O_CLOFORK) is closed in child on posix_spawn");
+CLOFORK_TEST(openclofork_posixspawn, open_via_openclofork, exec_via_posixspawn,
+    "open(O_CLOFORK) is closed in child on posix_spawn");
+CLOFORK_TEST(openfcntlclofork_posixspawn, open_via_openfcntlclofork,
+    exec_via_posixspawn,
+    "fcntl(open(...), F_SETFD, O_CLOFORK) is closed in child on posix_spawn");
+CLOFORK_TEST(pipe2wr_posixspawn, open_via_pipe2wr, exec_via_posixspawn,
+    "pipe2(O_CLOFORK) writer is closed in child on posix_spawn")
+CLOFORK_TEST(paccept_posixspawn, open_via_paccept, exec_via_posixspawn,
+    "paccept(..., SOCK_CLOFORK) is closed in child on posix_spawn")
+CLOFORK_TEST(socket_posixspawn, open_via_socket, exec_via_posixspawn,
+    "socket(SOCK_CLOFORK) is closed in child on posix_spawn")
+CLOFORK_TEST(socketpair0_posixspawn, open_via_socketpair0, exec_via_posixspawn,
+    "socketpair(SOCK_CLOFORK) side 0 is closed in child on posix_spawn")
+CLOFORK_TEST(socketpair1_posixspawn, open_via_socketpair1, exec_via_posixspawn,
+    "socketpair(SOCK_CLOFORK) side 1 is closed in child on posix_spawn")
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, accept4_posixspawn);
+	ATF_TP_ADD_TC(tp, clonedev_posixspawn);
+	ATF_TP_ADD_TC(tp, dup3_posixspawn);
+	ATF_TP_ADD_TC(tp, fcntldupfd_posixspawn);
+	ATF_TP_ADD_TC(tp, kqueue_posixspawn);
+	ATF_TP_ADD_TC(tp, openclofork_posixspawn);
+	ATF_TP_ADD_TC(tp, openfcntlclofork_posixspawn);
+	ATF_TP_ADD_TC(tp, paccept_posixspawn);
+	ATF_TP_ADD_TC(tp, pipe2rd_forkexecve);
+	ATF_TP_ADD_TC(tp, pipe2rd_posixspawn);
+	ATF_TP_ADD_TC(tp, pipe2rd_vforkexecve);
+	ATF_TP_ADD_TC(tp, pipe2wr_posixspawn);
+	ATF_TP_ADD_TC(tp, socket_posixspawn);
+	ATF_TP_ADD_TC(tp, socketpair0_posixspawn);
+	ATF_TP_ADD_TC(tp, socketpair1_posixspawn);
+
+	return atf_no_error();
+}
+
+#else	/* No O_CLOFORK */
+
+ATF_TC(not_implemented);
+ATF_TC_HEAD(not_implemented, tc)							   
+{
+	atf_tc_set_md_var(tc, "descr", "Unimplemented O_CLOFORK");
+}
+ATF_TC_BODY(not_implemented, tc)
+{
+	atf_tc_skip("close-on-fork not yet available");
+}
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, not_implemented);
+
+	return atf_no_error();
+}
+#endif
diff --git a/kernel/t_execregs.c b/kernel/t_execregs.c
new file mode 100644
index 000000000000..076a8de9547c
--- /dev/null
+++ b/kernel/t_execregs.c
@@ -0,0 +1,197 @@
+/*	$NetBSD: t_execregs.c,v 1.7 2025/04/27 14:30:03 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: t_execregs.c,v 1.7 2025/04/27 14:30:03 riastradh Exp $");
+
+#include <sys/wait.h>
+
+#include <atf-c.h>
+#include <err.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#ifdef HAVE_EXECREGS_TEST
+
+#include "execregs.h"
+#include "isqemu.h"
+#include "h_macros.h"
+
+static void
+readregs(int rfd, register_t regs[static NEXECREGS])
+{
+	uint8_t *p;
+	size_t n;
+	ssize_t nread;
+
+	p = (void *)regs;
+	n = NEXECREGS*sizeof(regs[0]);
+	while (n) {
+		RL(nread = read(rfd, p, n));
+		ATF_CHECK_MSG((size_t)nread <= n,
+		    "overlong read: %zu > %zu", (size_t)nread, n);
+		if (nread == 0)
+			break;
+		p += (size_t)nread;
+		n -= (size_t)nread;
+	}
+	ATF_CHECK_EQ_MSG(n, 0,
+	    "truncated read, missing %zu of %zu bytes",
+	    n, NEXECREGS*sizeof(regs[0]));
+}
+
+static void
+checkregs(const register_t regs[static NEXECREGS])
+{
+	unsigned i;
+
+#ifdef __hppa__
+	if (isQEMU()) {
+		atf_tc_expect_fail("PR port-hppa/59114: hppa:"
+		    " eager fpu switching for qemu and/or spectre mitigation");
+	}
+#endif
+
+	for (i = 0; i < NEXECREGS; i++) {
+		if (regs[i] != 0) {
+			for (i = 0; i < NEXECREGS; i++) {
+				fprintf(stderr, "[%s] %"PRIxREGISTER"\n",
+				    regname[i], regs[i]);
+			}
+			fprintf(stderr, "\n");
+			atf_tc_fail("registers not zeroed");
+		}
+	}
+}
+
+static void
+testregs(int child, const int pipefd[static 2],
+    register_t regs[static NEXECREGS])
+{
+	int status;
+
+	RL(close(pipefd[1]));
+
+	readregs(pipefd[0], regs);
+
+	RL(waitpid(child, &status, 0));
+	if (WIFSIGNALED(status)) {
+		atf_tc_fail_nonfatal("child terminated on signal %d (%s)",
+		    WTERMSIG(status), strsignal(WTERMSIG(status)));
+	} else if (!WIFEXITED(status)) {
+		atf_tc_fail_nonfatal("child terminated mysteriously,"
+		    " status=0x%x",
+		    status);
+	} else {
+		ATF_CHECK_MSG(WEXITSTATUS(status) == 0,
+		    "child exited with code %d", WEXITSTATUS(status));
+	}
+
+	checkregs(regs);
+}
+
+#endif
+
+ATF_TC(execregszero);
+ATF_TC_HEAD(execregszero, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Test execve(2) zeroes registers");
+}
+ATF_TC_BODY(execregszero, tc)
+{
+#ifdef HAVE_EXECREGS_TEST
+	char h_execregs[PATH_MAX];
+	int pipefd[2];
+	register_t regs[NEXECREGS];
+	pid_t child;
+
+	RL(snprintf(h_execregs, sizeof(h_execregs), "%s/h_execregs",
+		atf_tc_get_config_var(tc, "srcdir")));
+
+	RL(pipe(pipefd));
+	memset(regs, 0x5a, sizeof(regs));
+
+	RL(child = fork());
+	if (child == 0) {
+		if (dup2(pipefd[1], STDOUT_FILENO) == -1)
+			err(1, "dup2");
+		if (closefrom(STDERR_FILENO + 1) == -1)
+			err(1, "closefrom");
+		if (execregschild(h_execregs) == -1)
+			err(1, "execve");
+		_exit(2);
+	}
+
+	testregs(child, pipefd, regs);
+#else
+	atf_tc_skip("missing test for PR kern/59084:"
+	    " exec/spawn leaks register content");
+#endif
+}
+
+ATF_TC(spawnregszero);
+ATF_TC_HEAD(spawnregszero, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Test posix_spawn(2) zeroes registers");
+}
+ATF_TC_BODY(spawnregszero, tc)
+{
+#ifdef HAVE_EXECREGS_TEST
+	char h_execregs[PATH_MAX];
+	int pipefd[2];
+	register_t regs[NEXECREGS];
+	pid_t child;
+
+	RL(snprintf(h_execregs, sizeof(h_execregs), "%s/h_execregs",
+		atf_tc_get_config_var(tc, "srcdir")));
+
+	RL(pipe(pipefd));
+	memset(regs, 0x5a, sizeof(regs));
+
+	RL(child = spawnregschild(h_execregs, pipefd[1]));
+
+	testregs(child, pipefd, regs);
+#else
+	atf_tc_skip("missing test for PR kern/59084:"
+	    " exec/spawn leaks register content");
+#endif
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, execregszero);
+	ATF_TP_ADD_TC(tp, spawnregszero);
+
+	return atf_no_error();
+}
diff --git a/kernel/t_fdrestart.c b/kernel/t_fdrestart.c
new file mode 100644
index 000000000000..5449fcdaf18d
--- /dev/null
+++ b/kernel/t_fdrestart.c
@@ -0,0 +1,274 @@
+/*	$NetBSD: t_fdrestart.c,v 1.4 2023/11/18 19:46:55 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2023 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	_KMEMUSER		/* ERESTART */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: t_fdrestart.c,v 1.4 2023/11/18 19:46:55 riastradh Exp $");
+
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include <atf-c.h>
+#include <errno.h>
+#include <pthread.h>
+#include <unistd.h>
+
+#include <rump/rump.h>
+#include <rump/rump_syscalls.h>
+
+#include "h_macros.h"
+
+struct fdrestart {
+	void			(*op)(struct fdrestart *);
+	int			fd;
+	pthread_barrier_t	barrier;
+};
+
+static void
+waitforbarrier(struct fdrestart *F, const char *caller)
+{
+	int error;
+
+	error = pthread_barrier_wait(&F->barrier);
+	switch (error) {
+	case 0:
+	case PTHREAD_BARRIER_SERIAL_THREAD:
+		break;
+	default:
+		atf_tc_fail("%s: pthread_barrier_wait: %d, %s", caller, error,
+		    strerror(error));
+	}
+}
+
+static void
+doread(struct fdrestart *F)
+{
+	char c;
+	ssize_t nread;
+	int error;
+
+	/*
+	 * Wait for the other thread to be ready.
+	 */
+	waitforbarrier(F, "reader");
+
+	/*
+	 * Start a read.  This should block, and then, when the other
+	 * thread closes the fd, should be woken to fail with ERESTART.
+	 */
+	nread = rump_sys_read(F->fd, &c, sizeof(c));
+	ATF_REQUIRE_EQ_MSG(nread, -1, "nread=%zd", nread);
+	error = errno;
+	ATF_REQUIRE_EQ_MSG(error, ERESTART, "errno=%d (%s)", error,
+	    strerror(error));
+
+	/*
+	 * Now further attempts at I/O should fail with EBADF because
+	 * the fd has been closed.
+	 */
+	nread = rump_sys_read(F->fd, &c, sizeof(c));
+	ATF_REQUIRE_EQ_MSG(nread, -1, "nread=%zd", nread);
+	error = errno;
+	ATF_REQUIRE_EQ_MSG(error, EBADF, "errno=%d (%s)", error,
+	    strerror(error));
+}
+
+static void
+dowrite(struct fdrestart *F)
+{
+	static const char buf[1024*1024]; /* XXX >BIG_PIPE_SIZE */
+	ssize_t nwrit;
+	int error;
+
+	/*
+	 * Make sure the pipe's buffer is full first.
+	 */
+	for (;;) {
+		int nspace;
+
+		RL(rump_sys_ioctl(F->fd, FIONSPACE, &nspace));
+		ATF_REQUIRE_MSG(nspace >= 0, "nspace=%d", nspace);
+		if (nspace == 0)
+			break;
+		RL(rump_sys_write(F->fd, buf, (size_t)nspace));
+	}
+
+	/*
+	 * Wait for the other thread to be ready.
+	 */
+	waitforbarrier(F, "writer");
+
+	/*
+	 * Start a write.  This should block, and then, when the other
+	 * thread closes the fd, should be woken to fail with ERESTART.
+	 */
+	nwrit = rump_sys_write(F->fd, buf, sizeof(buf));
+	ATF_REQUIRE_EQ_MSG(nwrit, -1, "nwrit=%zd", nwrit);
+	error = errno;
+	ATF_REQUIRE_EQ_MSG(error, ERESTART, "errno=%d (%s)", error,
+	    strerror(error));
+
+	/*
+	 * Now further attempts at I/O should fail with EBADF because
+	 * the fd has been closed.
+	 */
+	nwrit = rump_sys_write(F->fd, buf, sizeof(buf));
+	ATF_REQUIRE_EQ_MSG(nwrit, -1, "nwrit=%zd", nwrit);
+	error = errno;
+	ATF_REQUIRE_EQ_MSG(error, EBADF, "errno=%d (%s)", error,
+	    strerror(error));
+}
+
+static void *
+doit(void *cookie)
+{
+	struct fdrestart *F = cookie;
+
+	(*F->op)(F);
+
+	return NULL;
+}
+
+static void
+on_sigalrm(int signo)
+{
+
+	atf_tc_fail("timed out");
+}
+
+static void
+testfdrestart(struct fdrestart *F)
+{
+	pthread_t t;
+
+	ATF_REQUIRE_MSG(signal(SIGALRM, &on_sigalrm) != SIG_ERR,
+	    "errno=%d (%s)", errno, strerror(errno));
+
+	RZ(pthread_barrier_init(&F->barrier, NULL, 2));
+	RZ(pthread_create(&t, NULL, &doit, F));
+	waitforbarrier(F, "closer");	/* wait for thread to start */
+	(void)sleep(1);			/* wait for op to start */
+	(void)alarm(1);			/* set a deadline */
+	RL(rump_sys_close(F->fd));	/* wake op in other thread */
+	RZ(pthread_join(t, NULL));	/* wait for op to wake and fail */
+	(void)alarm(0);			/* clear the deadline */
+}
+
+ATF_TC(pipe_read);
+ATF_TC_HEAD(pipe_read, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Test pipe read fails on close");
+}
+ATF_TC_BODY(pipe_read, tc)
+{
+	struct fdrestart fdrestart, *F = &fdrestart;
+	int fd[2];
+
+	rump_init();
+
+	RL(rump_sys_pipe(fd));
+
+	memset(F, 0, sizeof(*F));
+	F->op = &doread;
+	F->fd = fd[0];
+	testfdrestart(F);
+}
+
+ATF_TC(pipe_write);
+ATF_TC_HEAD(pipe_write, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Test pipe write fails on close");
+}
+ATF_TC_BODY(pipe_write, tc)
+{
+	struct fdrestart fdrestart, *F = &fdrestart;
+	int fd[2];
+
+	rump_init();
+
+	RL(rump_sys_pipe(fd));
+
+	memset(F, 0, sizeof(*F));
+	F->op = &dowrite;
+	F->fd = fd[1];
+	atf_tc_expect_fail("PR kern/57659");
+	testfdrestart(F);
+}
+
+ATF_TC(socketpair_read);
+ATF_TC_HEAD(socketpair_read, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Test socketpair read fails on close");
+}
+ATF_TC_BODY(socketpair_read, tc)
+{
+	struct fdrestart fdrestart, *F = &fdrestart;
+	int fd[2];
+
+	rump_init();
+
+	RL(rump_sys_socketpair(AF_LOCAL, SOCK_STREAM, 0, fd));
+
+	memset(F, 0, sizeof(*F));
+	F->op = &doread;
+	F->fd = fd[0];
+	testfdrestart(F);
+}
+
+ATF_TC(socketpair_write);
+ATF_TC_HEAD(socketpair_write, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Test socketpair write fails on close");
+}
+ATF_TC_BODY(socketpair_write, tc)
+{
+	struct fdrestart fdrestart, *F = &fdrestart;
+	int fd[2];
+
+	rump_init();
+
+	RL(rump_sys_socketpair(AF_LOCAL, SOCK_STREAM, 0, fd));
+
+	memset(F, 0, sizeof(*F));
+	F->op = &dowrite;
+	F->fd = fd[0];
+	testfdrestart(F);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, pipe_read);
+	ATF_TP_ADD_TC(tp, pipe_write);
+	ATF_TP_ADD_TC(tp, socketpair_read);
+	ATF_TP_ADD_TC(tp, socketpair_write);
+
+	return atf_no_error();
+}
diff --git a/kernel/t_nanosleep.c b/kernel/t_nanosleep.c
new file mode 100644
index 000000000000..9ef752b37e60
--- /dev/null
+++ b/kernel/t_nanosleep.c
@@ -0,0 +1,246 @@
+/* $NetBSD: t_nanosleep.c,v 1.2 2025/10/07 20:09:27 andvar Exp $ */
+
+/*-
+ * Copyright (c) 2024 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__COPYRIGHT("@(#) Copyright (c) 2024\
+ The NetBSD Foundation, inc. All rights reserved.");
+__RCSID("$NetBSD: t_nanosleep.c,v 1.2 2025/10/07 20:09:27 andvar Exp $");
+
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <atf-c.h>
+
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+
+static void
+sacrifice(void)
+{
+	pause();
+}
+
+static void
+tester(pid_t victim, clockid_t clock, int flags)
+{
+	/*
+	 * we need this sleep to be long enough that we
+	 * can accurately detect when the sleep finishes
+	 * early, but not so long that when there's no
+	 * bug and things actually sleep this long, that
+	 * the execution of a sleep this long, several
+	 * times, won't slow down the overall testing
+	 * process too much.    Trial and error...
+	 */
+	struct timespec to_sleep = { 4, 0 };
+
+	struct timespec before, after;
+	struct timespec *ts;
+	int e;
+
+	if (clock_gettime(clock, &before) != 0)
+		exit(1);
+
+	if (flags & TIMER_ABSTIME) {
+		timespecadd(&to_sleep, &before, &after);
+		ts = &after;
+	} else
+		ts = &to_sleep;
+
+	printf("Test: Clock=%d Flags=%x, starting at %jd.%.9ld\n",
+		(int)clock, flags, (intmax_t)before.tv_sec, before.tv_nsec);
+	if (flags & TIMER_ABSTIME)
+		printf("Sleeping until %jd.%.9ld\n",
+		    (intmax_t)ts->tv_sec, ts->tv_nsec);
+	else
+		printf("Sleeping for %jd.%.9ld\n",
+		    (intmax_t)ts->tv_sec, ts->tv_nsec);
+
+	/* OK, we're ready */
+
+	/* these next two steps need to be as close together as possible */
+	if (kill(victim, SIGKILL) == -1)
+		exit(2);
+	if ((e = clock_nanosleep(clock, flags, ts, &after)) != 0)
+		exit(20 + e);
+
+	if (!(flags & TIMER_ABSTIME)) {
+		printf("Remaining to sleep: %jd.%.9ld\n",
+		    (intmax_t)after.tv_sec, after.tv_nsec);
+
+		if (after.tv_sec != 0 || after.tv_nsec != 0)
+			exit(3);
+	}
+
+	if (clock_gettime(clock, &after) != 0)
+		exit(4);
+
+	printf("Sleep ended at: %jd.%.9ld\n",
+		(intmax_t)after.tv_sec, after.tv_nsec);
+
+	timespecadd(&before, &to_sleep, &before);
+	if (timespeccmp(&before, &after, >))
+		exit(5);
+
+	exit(0);
+}
+
+/*
+ * The parent of the masochist/victim above, controls everything.
+ */
+static void
+runit(clockid_t clock, int flags)
+{
+	pid_t v, m, x;
+	int status;
+	struct timespec brief = { 0, 3 * 100 * 1000 * 1000 };  /* 300 ms */
+
+	ATF_REQUIRE((v = fork()) != -1);
+	if (v == 0)
+		sacrifice();
+
+	ATF_REQUIRE((m = fork()) != -1);
+	if (m == 0)
+		tester(v, clock, flags);
+
+	ATF_REQUIRE((x = wait(&status)) != -1);
+
+	if (x == m) {
+		/*
+		 * This is bad, the murderer shouldn't die first
+		 */
+		fprintf(stderr, "M exited first, status %#x\n", status);
+		(void)kill(v, SIGKILL);	/* just in case */
+		atf_tc_fail("2nd child predeceased first");
+	}
+	if (x != v) {
+		fprintf(stderr, "Unknown exit from %d (status: %#x)"
+		    "(M=%d V=%d)\n", x, status, m, v);
+		(void)kill(m, SIGKILL);
+		(void)kill(v, SIGKILL);
+		atf_tc_fail("Strange child died");
+	}
+
+	/*
+	 * OK, the victim died, we don't really care why,
+	 * (it should have been because of a SIGKILL, maybe
+	 * test for that someday).
+	 *
+	 * Now we get to proceed to the real test.
+	 *
+	 * But we want to wait a short while to try and be sure
+	 * that m (the child still running) has a chance to
+	 * fall asleep.
+	 */
+	(void) clock_nanosleep(CLOCK_MONOTONIC, TIMER_RELTIME, &brief, NULL);
+
+	/*
+	 * This is the test, for PR kern/58733
+	 *   -  stop a process while in clock_nanosleep()
+	 *   -  resume it again
+	 *   -  see if it still sleeps as long as was requested (or longer)
+	 */
+	ATF_REQUIRE(kill(m, SIGSTOP) == 0);
+	(void) clock_nanosleep(CLOCK_MONOTONIC, TIMER_RELTIME, &brief, NULL);
+	ATF_REQUIRE(kill(m, SIGCONT) == 0);
+
+	ATF_REQUIRE((x = wait(&status)) != -1);
+
+	if (x != m) {
+		fprintf(stderr, "Unknown exit from %d (status: %#x)"
+		    "(M=%d V=%d)\n", x, status, m, v);
+		(void) kill(m, SIGKILL);
+		atf_tc_fail("Strange child died");
+	}
+
+	if (status == 0)
+		atf_tc_pass();
+
+	/*
+	 * Here we should decode the status, and give a better
+	 * clue what really went wrong.   Later...
+	 */
+	fprintf(stderr, "Test failed: status from M: %#x\n", status);
+	atf_tc_fail("M exited with non-zero status.  PR kern/58733");
+}
+
+
+ATF_TC(nanosleep_monotonic_absolute);
+ATF_TC_HEAD(nanosleep_monotonic_absolute, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Checks clock_nanosleep(MONO, ABS)");
+}
+ATF_TC_BODY(nanosleep_monotonic_absolute, tc)
+{
+	runit(CLOCK_MONOTONIC, TIMER_ABSTIME);
+}
+
+ATF_TC(nanosleep_monotonic_relative);
+ATF_TC_HEAD(nanosleep_monotonic_relative, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Checks clock_nanosleep(MONO, REL)");
+}
+ATF_TC_BODY(nanosleep_monotonic_relative, tc)
+{
+	runit(CLOCK_MONOTONIC, TIMER_RELTIME);
+}
+
+ATF_TC(nanosleep_realtime_absolute);
+ATF_TC_HEAD(nanosleep_realtime_absolute, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Checks clock_nanosleep(REAL, ABS)");
+}
+ATF_TC_BODY(nanosleep_realtime_absolute, tc)
+{
+	runit(CLOCK_REALTIME, TIMER_ABSTIME);
+}
+
+ATF_TC(nanosleep_realtime_relative);
+ATF_TC_HEAD(nanosleep_realtime_relative, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Checks clock_nanosleep(REAL, REL)");
+}
+ATF_TC_BODY(nanosleep_realtime_relative, tc)
+{
+	runit(CLOCK_REALTIME, TIMER_RELTIME);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, nanosleep_monotonic_absolute);
+	ATF_TP_ADD_TC(tp, nanosleep_monotonic_relative);
+	ATF_TP_ADD_TC(tp, nanosleep_realtime_absolute);
+	ATF_TP_ADD_TC(tp, nanosleep_realtime_relative);
+
+	return atf_no_error();
+}
diff --git a/kernel/t_semtimedop.c b/kernel/t_semtimedop.c
new file mode 100644
index 000000000000..daeaac6b3dab
--- /dev/null
+++ b/kernel/t_semtimedop.c
@@ -0,0 +1,279 @@
+/*	$NetBSD: t_semtimedop.c,v 1.2 2024/10/10 07:45:02 martin Exp $	*/
+
+/*-
+ * Copyright (c) 2024 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: t_semtimedop.c,v 1.2 2024/10/10 07:45:02 martin Exp $");
+
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <errno.h>
+#include <string.h>
+#include <time.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <atf-c.h>
+#include <sys/wait.h>
+
+union semun {
+	int	val;		/* value for SETVAL */
+	struct	semid_ds *buf;	/* buffer for IPC_{STAT,SET} */
+	u_short	*array;		/* array for GETALL & SETALL */
+};
+
+ATF_TC(semtimedop_basic);
+ATF_TC_HEAD(semtimedop_basic, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "Basic semtimedop functionality");
+}
+
+ATF_TC_BODY(semtimedop_basic, tc)
+{
+	key_t		key = IPC_PRIVATE;
+	int		semid;
+	struct sembuf	sops;
+	union semun	sun;
+	struct timespec	timeout;
+
+	/* Create semaphore set with 1 semaphore */
+	semid = semget(key, 1, IPC_CREAT | 0600);
+	ATF_REQUIRE_MSG(semid != -1, "semget failed: %s", strerror(errno));
+
+	/* Initialize semaphore to 0 */
+	sun.val = 0;
+	if (semctl(semid, 0, SETVAL, sun) == -1) {
+		ATF_REQUIRE_MSG(0, "semctl SETVAL failed: %s",
+		    strerror(errno));
+	}
+
+	/* Define semtimedop operation: increment semaphore */
+	sops.sem_num = 0;
+	sops.sem_op = 1;
+	sops.sem_flg = 0;
+
+	/* Define timeout */
+	timeout.tv_sec = 1;
+	timeout.tv_nsec = 0;
+
+	/* Perform semtimedop */
+	if (semtimedop(semid, &sops, 1, &timeout) == -1) {
+		ATF_REQUIRE_MSG(0, "semtimedop failed: %s", strerror(errno));
+	}
+
+	/* Check semaphore value */
+	int val = semctl(semid, 0, GETVAL);
+	ATF_REQUIRE_MSG(val == 1,
+	    "Semaphore value incorrect: got %d, expected 1", val);
+
+	/* Clean up */
+	ATF_REQUIRE_MSG(semctl(semid, 0, IPC_RMID) != -1,
+	    "semctl IPC_RMID failed: %s", strerror(errno));
+}
+
+/* semtimedop blocks until timeout expires */
+ATF_TC(semtimedop_timeout);
+ATF_TC_HEAD(semtimedop_timeout, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "semtimedop blocks until timeout expires");
+}
+
+ATF_TC_BODY(semtimedop_timeout, tc)
+{
+	key_t		key = IPC_PRIVATE;
+	int		semid;
+	struct sembuf	sops;
+	union semun	sun;
+	struct timespec	timeout;
+	pid_t		pid;
+	int		status;
+
+	/* Create semaphore set with 1 semaphore */
+	semid = semget(key, 1, IPC_CREAT | 0600);
+	ATF_REQUIRE_MSG(semid != -1, "semget failed: %s", strerror(errno));
+
+	/* Initialize semaphore to 0 */
+	sun.val = 0;
+	if (semctl(semid, 0, SETVAL, sun) == -1) {
+		ATF_REQUIRE_MSG(0, "semctl SETVAL failed: %s", strerror(errno));
+	}
+
+	pid = fork();
+	ATF_REQUIRE_MSG(pid != -1, "fork failed: %s", strerror(errno));
+
+	if (pid == 0) {
+		/*
+		 * Child: perform semtimedop with negative sem_op, should
+		 * block until timeout
+		 */
+		sops.sem_num = 0;
+		sops.sem_op = -1;
+		sops.sem_flg = 0;
+
+		timeout.tv_sec = 2;
+		timeout.tv_nsec = 0;
+
+		if (semtimedop(semid, &sops, 1, &timeout) == -1) {
+			if (errno == EAGAIN || errno == EINTR) {
+				exit(0);	/* Expected */
+			}
+		}
+		exit(1);	/* Unexpected failure/success */
+	}
+
+	/* Parent: wait for child to finish */
+	waitpid(pid, &status, 0);
+	ATF_REQUIRE(WIFEXITED(status));
+	ATF_REQUIRE_EQ(WEXITSTATUS(status), 0);
+
+	/* Clean up */
+	ATF_REQUIRE_MSG(semctl(semid, 0, IPC_RMID) != -1,
+	    "semctl IPC_RMID failed: %s", strerror(errno));
+}
+
+/* semtimedop with SEM_UNDO adjusts semaphore on exit */
+ATF_TC(semtimedop_semundo);
+ATF_TC_HEAD(semtimedop_semundo, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "semtimedop with SEM_UNDO adjusts semaphore on exit");
+}
+
+ATF_TC_BODY(semtimedop_semundo, tc)
+{
+	key_t		key = IPC_PRIVATE;
+	int		semid;
+	struct sembuf	sops;
+	union semun	sun;
+	struct timespec	timeout;
+	pid_t		pid;
+	int		val;
+
+	/* Create semaphore set with 1 semaphore */
+	semid = semget(key, 1, IPC_CREAT | 0600);
+	ATF_REQUIRE_MSG(semid != -1, "semget failed: %s", strerror(errno));
+
+	/* Initialize semaphore to 0 */
+	sun.val = 0;
+	if (semctl(semid, 0, SETVAL, sun) == -1) {
+		ATF_REQUIRE_MSG(0, "semctl SETVAL failed: %s", strerror(errno));
+	}
+
+	pid = fork();
+	ATF_REQUIRE_MSG(pid != -1, "fork failed: %s", strerror(errno));
+
+	if (pid == 0) {
+		/* Child: perform semtimedop with SEM_UNDO */
+		sops.sem_num = 0;
+		sops.sem_op = 1;
+		sops.sem_flg = SEM_UNDO;
+
+		timeout.tv_sec = 1;
+		timeout.tv_nsec = 0;
+
+		if (semtimedop(semid, &sops, 1, &timeout) == -1) {
+			exit(1);	/* Unexpected failure */
+		}
+
+		exit(0); /* Exit normally, SEM_UNDO should be triggered */
+	}
+
+	/* Parent: wait for child to exit */
+	waitpid(pid, NULL, 0);
+
+	/* Check semaphore value; should be 0 after SEM_UNDO */
+	val = semctl(semid, 0, GETVAL);
+	ATF_REQUIRE_MSG(val == 0,
+	    "Semaphore value incorrect after SEM_UNDO: got %d, "
+	    "expected 0", val);
+
+	/* Clean up */
+	ATF_REQUIRE_MSG(semctl(semid, 0, IPC_RMID) != -1,
+	    "semctl IPC_RMID failed: %s", strerror(errno));
+}
+
+/* semtimedop handles invalid parameters correctly */
+ATF_TC(semtimedop_invalid);
+ATF_TC_HEAD(semtimedop_invalid, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "semtimedop handles invalid parameters correctly");
+}
+
+ATF_TC_BODY(semtimedop_invalid, tc)
+{
+	struct sembuf	sops;
+	union semun	sun;
+	struct timespec	timeout;
+
+	/* Invalid semaphore id */
+	sops.sem_num = 0;
+	sops.sem_op = -1;
+	sops.sem_flg = 0;
+
+	timeout.tv_sec = 1;
+	timeout.tv_nsec = 0;
+
+	/* Attempt to perform semtimedop on invalid semid */
+	ATF_REQUIRE_MSG(semtimedop(-1, &sops, 1, &timeout) == -1
+	    && errno == EINVAL, "semtimedop did not fail on invalid semid");
+
+	/* Create semaphore set */
+	key_t	key = IPC_PRIVATE;
+	int	semid = semget(key, 1, IPC_CREAT | 0600);
+	ATF_REQUIRE_MSG(semid != -1, "semget failed: %s", strerror(errno));
+
+	/* Initialize semaphore to 0 */
+	sun.val = 0;
+	if (semctl(semid, 0, SETVAL, sun) == -1) {
+		ATF_REQUIRE_MSG(0, "semctl SETVAL failed: %s", strerror(errno));
+	}
+
+	/* Set an invalid semaphore number */
+	sops.sem_num = 1;	/* Only 1 semaphore in set, index 0 */
+	sops.sem_op = 1;
+	sops.sem_flg = 0;
+
+	/* Attempt semtimedop with invalid sem_num */
+	ATF_REQUIRE_MSG(semtimedop(semid, &sops, 1, &timeout) == -1
+	    && errno == EFBIG, "semtimedop did not fail on invalid sem_num");
+
+	/* Clean up */
+	ATF_REQUIRE_MSG(semctl(semid, 0, IPC_RMID) != -1,
+	    "semctl IPC_RMID failed: %s", strerror(errno));
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, semtimedop_basic);
+	ATF_TP_ADD_TC(tp, semtimedop_timeout);
+	ATF_TP_ADD_TC(tp, semtimedop_semundo);
+	ATF_TP_ADD_TC(tp, semtimedop_invalid);
+
+	return atf_no_error();
+}
diff --git a/kernel/t_setjmp.sh b/kernel/t_setjmp.sh
new file mode 100644
index 000000000000..1dbbd8504234
--- /dev/null
+++ b/kernel/t_setjmp.sh
@@ -0,0 +1,63 @@
+#	$NetBSD: t_setjmp.sh,v 1.5 2025/04/29 10:57:17 martin Exp $
+#
+# Copyright (c) 2025 The NetBSD Foundation, Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+# ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+
+module_loaded=no
+atf_test_case setjmp cleanup
+setjmp_head()
+{
+	atf_set "descr" "Test setjmp(9)/longjmp(9)"
+}
+setjmp_body()
+{
+	case `uname -p` in
+	vax)
+		atf_expect_fail "PR port-vax/59308:" \
+		    " kernel longjmp(9) fails to make setjmp(9) return 1"
+		;;
+	esac
+
+	err=$( modstat -e 2>&1 )
+	if [ $? -gt 0 ]; then
+		atf_skip "${err##modstat:}"
+	fi
+
+	module_loaded="yes"
+	modload "$(atf_get_srcdir)/setjmp_tester/setjmp_tester.kmod"
+	atf_check -s exit:0 -o inline:'1\n' \
+	    sysctl -n -w kern.setjmp_tester.test=1
+}
+setjmp_cleanup()
+{
+	if [ "${module_loaded}" != "no" ]; then
+		modunload setjmp_tester
+	fi
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case setjmp
+}
diff --git a/kernel/t_signal_and_sp.c b/kernel/t_signal_and_sp.c
new file mode 100644
index 000000000000..1cef56cd3041
--- /dev/null
+++ b/kernel/t_signal_and_sp.c
@@ -0,0 +1,628 @@
+/*	$NetBSD: t_signal_and_sp.c,v 1.21 2025/04/26 23:49:55 uwe Exp $	*/
+
+/*
+ * Copyright (c) 2024 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	__EXPOSE_STACK	/* <sys/param.h>: expose STACK_ALIGNBYTES */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: t_signal_and_sp.c,v 1.21 2025/04/26 23:49:55 uwe Exp $");
+
+#include <sys/param.h>
+#include <sys/wait.h>
+
+#include <atf-c.h>
+#include <limits.h>
+#include <poll.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <ucontext.h>
+#include <unistd.h>
+
+#include "h_execsp.h"
+#include "h_macros.h"
+
+#ifdef HAVE_STACK_POINTER_H
+#  include "stack_pointer.h"
+#endif
+
+#define PR_59327 "PR kern/59327: user stack pointer is not aligned properly"
+
+#ifdef HAVE_SIGNALSPHANDLER
+void signalsphandler(int);	/* signalsphandler.S assembly routine */
+#endif
+
+void *volatile signalsp;
+
+static void
+test_execsp(const struct atf_tc *tc, const char *prog)
+{
+#ifdef STACK_ALIGNBYTES
+	char h_execsp[PATH_MAX];
+	struct execsp execsp;
+	int fd[2];
+	pid_t pid;
+	struct pollfd pollfd;
+	int nfds;
+	ssize_t nread;
+	int status;
+
+	/*
+	 * Determine the full path to the helper program.
+	 */
+	RL(snprintf(h_execsp, sizeof(h_execsp), "%s/%s",
+		atf_tc_get_config_var(tc, "srcdir"), prog));
+
+	/*
+	 * Create a pipe to read a bundle of stack pointer samples from
+	 * the child, and fork the child.
+	 */
+	RL(pipe(fd));
+	RL(pid = vfork());
+	if (pid == 0) {		/* child */
+		char *const argv[] = {h_execsp, NULL};
+
+		if (dup2(fd[1], STDOUT_FILENO) == -1)
+			_exit(1);
+		if (closefrom(STDERR_FILENO + 1) == -1)
+			_exit(2);
+		if (execve(argv[0], argv, NULL) == -1)
+			_exit(3);
+		_exit(4);
+	}
+
+	/*
+	 * Close the writing end so, if something goes wrong in the
+	 * child, we don't hang indefinitely waiting for output.
+	 */
+	RL(close(fd[1]));
+
+	/*
+	 * Wait up to 5sec for the child to return an answer.  Any more
+	 * than that, and we kill it.  The child is mostly hand-written
+	 * assembly routines where lots can go wrong, so don't bother
+	 * waiting if it gets stuck in a loop.
+	 */
+	pollfd.fd = fd[0];
+	pollfd.events = POLLIN;
+	RL(nfds = poll(&pollfd, 1, 5*1000/*ms*/));
+	if (nfds == 0) {
+		fprintf(stderr, "child hung, killing\n");
+		RL(kill(pid, SIGKILL));
+	}
+
+	/*
+	 * Read a bundle of stack pointer samples from the child.
+	 */
+	RL(nread = read(fd[0], &execsp, sizeof(execsp)));
+	ATF_CHECK_MSG((size_t)nread == sizeof(execsp),
+	    "nread=%zu sizeof(execsp)=%zu",
+	    (size_t)nread, sizeof(execsp));
+
+	/*
+	 * Wait for the child to terminate and report failure if it
+	 * didn't exit cleanly.
+	 */
+	RL(waitpid(pid, &status, 0));
+	if (WIFSIGNALED(status)) {
+		atf_tc_fail_nonfatal("child exited on signal %d (%s)",
+		    WTERMSIG(status), strsignal(WTERMSIG(status)));
+	} else if (!WIFEXITED(status)) {
+		atf_tc_fail_nonfatal("child exited status=0x%x", status);
+	} else {
+		ATF_CHECK_MSG(WEXITSTATUS(status) == 0,
+		    "child exited with code %d",
+		    WEXITSTATUS(status));
+	}
+
+	/*
+	 * Now that we have reaped the child, stop here if the stack
+	 * pointer samples are bogus; otherwise verify they are all
+	 * aligned.
+	 */
+	if ((size_t)nread != sizeof(execsp))
+		return;		/* failed already */
+
+	printf("start sp @ %p\n", execsp.startsp);
+	printf("ctor sp @ %p\n", execsp.ctorsp);
+	printf("main sp @ %p\n", execsp.mainsp);
+	printf("dtor sp @ %p\n", execsp.dtorsp);
+
+	ATF_CHECK_MSG(((uintptr_t)execsp.startsp & STACK_ALIGNBYTES) == 0,
+	    "elf entry point was called with misaligned sp: %p",
+	    execsp.startsp);
+
+	ATF_CHECK_MSG(((uintptr_t)execsp.ctorsp & STACK_ALIGNBYTES) == 0,
+	    "elf constructor was called with misaligned sp: %p",
+	    execsp.ctorsp);
+
+	ATF_CHECK_MSG(((uintptr_t)execsp.mainsp & STACK_ALIGNBYTES) == 0,
+	    "main function was called with misaligned sp: %p",
+	    execsp.mainsp);
+
+	ATF_CHECK_MSG(((uintptr_t)execsp.dtorsp & STACK_ALIGNBYTES) == 0,
+	    "elf destructor was called with misaligned sp: %p",
+	    execsp.dtorsp);
+
+	/*
+	 * Leave a reminder on architectures for which we haven't
+	 * implemented execsp_start.S.
+	 */
+	if (execsp.startsp == NULL ||
+	    execsp.ctorsp == NULL ||
+	    execsp.mainsp == NULL ||
+	    execsp.dtorsp == NULL)
+		atf_tc_skip("Not fully supported on this architecture");
+#else
+	atf_tc_skip("Unknown STACK_ALIGNBYTES on this architecture");
+#endif
+}
+
+ATF_TC(execsp_dynamic);
+ATF_TC_HEAD(execsp_dynamic, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Verify stack pointer is aligned on dynamic program start");
+}
+ATF_TC_BODY(execsp_dynamic, tc)
+{
+	test_execsp(tc, "h_execsp_dynamic");
+}
+
+ATF_TC(execsp_static);
+ATF_TC_HEAD(execsp_static, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Verify stack pointer is aligned on static program start");
+}
+ATF_TC_BODY(execsp_static, tc)
+{
+	test_execsp(tc, "h_execsp_static");
+}
+
+#if defined STACK_ALIGNBYTES && defined HAVE_CONTEXTSPFUNC
+void *volatile contextsp;	/* set by contextspfunc.S */
+static ucontext_t return_context;
+static volatile bool test_context_done;
+
+void contextspfunc(void);	/* contextspfunc.S assembly routine */
+
+static void
+contextnoop(void)
+{
+
+	fprintf(stderr, "contextnoop\n");
+	/* control will return to contextspfunc via uc_link */
+}
+
+void contextdone(void);		/* called by contextspfunc.S */
+void
+contextdone(void)
+{
+
+	fprintf(stderr, "contextdone\n");
+	ATF_REQUIRE(!test_context_done);
+	test_context_done = true;
+	RL(setcontext(&return_context));
+	atf_tc_fail("setcontext returned");
+}
+#endif
+
+ATF_TC(contextsp);
+ATF_TC_HEAD(contextsp, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Verify stack pointer is aligned on makecontext entry");
+}
+ATF_TC_BODY(contextsp, tc)
+{
+#if defined STACK_ALIGNBYTES && defined HAVE_CONTEXTSPFUNC
+	ucontext_t uc;
+	char *stack;
+	unsigned i;
+
+	REQUIRE_LIBC(stack = malloc(SIGSTKSZ + STACK_ALIGNBYTES), NULL);
+	fprintf(stderr, "stack @ [%p,%p)\n", stack,
+	    stack + SIGSTKSZ + STACK_ALIGNBYTES);
+
+	for (i = 0; i <= STACK_ALIGNBYTES; i++) {
+		contextsp = NULL;
+		test_context_done = false;
+
+		RL(getcontext(&uc));
+		uc.uc_stack.ss_sp = stack;
+		uc.uc_stack.ss_size = SIGSTKSZ + i;
+		makecontext(&uc, &contextspfunc, 0);
+
+		fprintf(stderr, "[%u] swapcontext\n", i);
+		RL(swapcontext(&return_context, &uc));
+
+		ATF_CHECK(contextsp != NULL);
+		ATF_CHECK_MSG((uintptr_t)stack <= (uintptr_t)contextsp &&
+		    (uintptr_t)contextsp <= (uintptr_t)stack + SIGSTKSZ + i,
+		    "contextsp=%p", contextsp);
+		ATF_CHECK_MSG(((uintptr_t)contextsp & STACK_ALIGNBYTES) == 0,
+		    "[%u] makecontext function called with misaligned sp %p",
+		    i, contextsp);
+	}
+
+	for (i = 0; i <= STACK_ALIGNBYTES; i++) {
+		contextsp = NULL;
+		test_context_done = false;
+
+		RL(getcontext(&uc));
+		uc.uc_stack.ss_sp = stack + i;
+		uc.uc_stack.ss_size = SIGSTKSZ;
+		makecontext(&uc, &contextspfunc, 0);
+
+		fprintf(stderr, "[%u] swapcontext\n", i);
+		RL(swapcontext(&return_context, &uc));
+
+		ATF_CHECK(contextsp != NULL);
+		ATF_CHECK_MSG((uintptr_t)stack + i <= (uintptr_t)contextsp &&
+		    (uintptr_t)contextsp <= (uintptr_t)stack + i + SIGSTKSZ,
+		    "contextsp=%p", contextsp);
+		ATF_CHECK_MSG(((uintptr_t)contextsp & STACK_ALIGNBYTES) == 0,
+		    "[%u] makecontext function called with misaligned sp %p",
+		    i, contextsp);
+	}
+#else
+	atf_tc_skip("Not implemented on this platform");
+#endif
+}
+
+ATF_TC(contextsplink);
+ATF_TC_HEAD(contextsplink, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Verify stack pointer is aligned on makecontext link entry");
+}
+ATF_TC_BODY(contextsplink, tc)
+{
+#if defined STACK_ALIGNBYTES && defined HAVE_CONTEXTSPFUNC
+	ucontext_t uc1, uc2;
+	char *stack1, *stack2;
+	unsigned i;
+
+	REQUIRE_LIBC(stack1 = malloc(SIGSTKSZ), NULL);
+	fprintf(stderr, "stack1 @ [%p,%p)\n", stack1, stack1 + SIGSTKSZ);
+	REQUIRE_LIBC(stack2 = malloc(SIGSTKSZ + STACK_ALIGNBYTES), NULL);
+	fprintf(stderr, "stack2 @ [%p,%p)\n",
+	    stack2, stack2 + SIGSTKSZ + STACK_ALIGNBYTES);
+
+	for (i = 0; i <= STACK_ALIGNBYTES; i++) {
+		contextsp = NULL;
+		test_context_done = false;
+
+		RL(getcontext(&uc1));
+		uc1.uc_stack.ss_sp = stack1;
+		uc1.uc_stack.ss_size = SIGSTKSZ;
+		uc1.uc_link = &uc2;
+		makecontext(&uc1, &contextnoop, 0);
+
+		RL(getcontext(&uc2));
+		uc2.uc_stack.ss_sp = stack2;
+		uc2.uc_stack.ss_size = SIGSTKSZ + i;
+		makecontext(&uc2, &contextspfunc, 0);
+
+		fprintf(stderr, "[%u] swapcontext\n", i);
+		RL(swapcontext(&return_context, &uc1));
+
+		ATF_CHECK(contextsp != NULL);
+		ATF_CHECK_MSG((uintptr_t)stack2 <= (uintptr_t)contextsp &&
+		    (uintptr_t)contextsp <= (uintptr_t)stack2 + SIGSTKSZ + i,
+		    "contextsp=%p", contextsp);
+		ATF_CHECK_MSG(((uintptr_t)contextsp & STACK_ALIGNBYTES) == 0,
+		    "[%u] makecontext function called with misaligned sp %p",
+		    i, contextsp);
+	}
+
+	for (i = 0; i <= STACK_ALIGNBYTES; i++) {
+		contextsp = NULL;
+		test_context_done = false;
+
+		RL(getcontext(&uc1));
+		uc1.uc_stack.ss_sp = stack1;
+		uc1.uc_stack.ss_size = SIGSTKSZ;
+		uc1.uc_link = &uc2;
+		makecontext(&uc1, &contextnoop, 0);
+
+		RL(getcontext(&uc2));
+		uc2.uc_stack.ss_sp = stack2 + i;
+		uc2.uc_stack.ss_size = SIGSTKSZ;
+		makecontext(&uc2, &contextspfunc, 0);
+
+		fprintf(stderr, "[%u] swapcontext\n", i);
+		RL(swapcontext(&return_context, &uc1));
+
+		ATF_CHECK(contextsp != NULL);
+		ATF_CHECK_MSG((uintptr_t)stack2 + i <= (uintptr_t)contextsp &&
+		    (uintptr_t)contextsp <= (uintptr_t)stack2 + SIGSTKSZ + i,
+		    "contextsp=%p", contextsp);
+		ATF_CHECK_MSG(((uintptr_t)contextsp & STACK_ALIGNBYTES) == 0,
+		    "[%u] makecontext function called with misaligned sp %p",
+		    i, contextsp);
+	}
+#else
+	atf_tc_skip("Not implemented on this platform");
+#endif
+}
+
+ATF_TC(signalsp);
+ATF_TC_HEAD(signalsp, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Verify stack pointer is aligned on entry to signal handler");
+}
+ATF_TC_BODY(signalsp, tc)
+{
+#if defined STACK_ALIGNBYTES && defined HAVE_SIGNALSPHANDLER
+	struct sigaction sa;
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = &signalsphandler;
+	RL(sigaction(SIGUSR1, &sa, NULL));
+	RL(raise(SIGUSR1));
+
+	ATF_CHECK_MSG(((uintptr_t)signalsp & STACK_ALIGNBYTES) == 0,
+	    "signal handler was called with a misaligned sp: %p",
+	    signalsp);
+#else
+	atf_tc_skip("Not implemented on this platform");
+#endif
+}
+
+ATF_TC(signalsp_sigaltstack);
+ATF_TC_HEAD(signalsp_sigaltstack, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Verify stack pointer is aligned on entry to signal handler"
+	    " with maximally misaligned sigaltstack");
+}
+ATF_TC_BODY(signalsp_sigaltstack, tc)
+{
+#if defined STACK_ALIGNBYTES && HAVE_SIGNALSPHANDLER
+#if defined(__sh__)
+	atf_tc_expect_fail(PR_59327);
+#endif
+	char *stack;
+	struct sigaction sa;
+	struct sigaltstack ss;
+	unsigned i;
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = &signalsphandler;
+	sa.sa_flags = SA_ONSTACK;
+	RL(sigaction(SIGUSR1, &sa, NULL));
+
+	/*
+	 * Allocate a signal stack with enough slop to try all possible
+	 * misalignments of the stack pointer.  Print it to stderr so
+	 * it always appears in atf output before shenanigans happen.
+	 */
+	REQUIRE_LIBC(stack = malloc(SIGSTKSZ + STACK_ALIGNBYTES), NULL);
+	fprintf(stderr, "stack @ [%p, %p)\n",
+	    stack, stack + SIGSTKSZ + STACK_ALIGNBYTES);
+
+	/*
+	 * Try with all alignments of high addresses.
+	 */
+	for (i = 0; i <= STACK_ALIGNBYTES; i++) {
+		ss.ss_sp = stack;
+		ss.ss_size = SIGSTKSZ + i;
+		ss.ss_flags = 0;
+		RL(sigaltstack(&ss, NULL));
+
+		signalsp = NULL;
+		RL(raise(SIGUSR1));
+		ATF_CHECK(signalsp != NULL);
+		ATF_CHECK_MSG((uintptr_t)stack <= (uintptr_t)signalsp &&
+		    (uintptr_t)signalsp <= (uintptr_t)stack + SIGSTKSZ + i,
+		    "signalsp=%p", signalsp);
+		ATF_CHECK_MSG(((uintptr_t)signalsp & STACK_ALIGNBYTES) == 0,
+		    "[%u] signal handler was called with a misaligned sp: %p",
+		    i, signalsp);
+	}
+
+	/*
+	 * Try with all alignments of low addresses.
+	 */
+	for (i = 0; i <= STACK_ALIGNBYTES; i++) {
+		ss.ss_sp = stack + i;
+		ss.ss_size = SIGSTKSZ;
+		ss.ss_flags = 0;
+		RL(sigaltstack(&ss, NULL));
+
+		signalsp = NULL;
+		RL(raise(SIGUSR1));
+		ATF_CHECK(signalsp != NULL);
+		ATF_CHECK_MSG((uintptr_t)stack + i <= (uintptr_t)signalsp &&
+		    (uintptr_t)signalsp <= (uintptr_t)stack + i + SIGSTKSZ,
+		    "signalsp=%p", signalsp);
+		ATF_CHECK_MSG(((uintptr_t)signalsp & STACK_ALIGNBYTES) == 0,
+		    "[%u] signal handler was called with a misaligned sp: %p",
+		    i, signalsp);
+	}
+#else
+	atf_tc_skip("Not implemented on this platform");
+#endif
+}
+
+#if defined STACK_ALIGNBYTES && defined HAVE_THREADSPFUNC
+void *threadspfunc(void *);	/* threadspfunc.S assembly routine */
+#endif
+
+ATF_TC(threadsp);
+ATF_TC_HEAD(threadsp, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Verify stack pointer is aligned on thread start");
+}
+ATF_TC_BODY(threadsp, tc)
+{
+#if defined STACK_ALIGNBYTES && defined HAVE_THREADSPFUNC
+	pthread_t t;
+	void *sp;
+	char *stack;
+	unsigned i;
+
+	REQUIRE_LIBC(stack = malloc(SIGSTKSZ + STACK_ALIGNBYTES), NULL);
+	fprintf(stderr, "stack @ [%p,%p)\n", stack,
+	    stack + SIGSTKSZ + STACK_ALIGNBYTES);
+
+	RZ(pthread_create(&t, NULL, &threadspfunc, NULL));
+
+	alarm(1);
+	RZ(pthread_join(t, &sp));
+	alarm(0);
+
+	ATF_CHECK(sp != NULL);
+	ATF_CHECK_MSG(((uintptr_t)sp & STACK_ALIGNBYTES) == 0,
+	    "thread called with misaligned sp: %p", sp);
+
+	for (i = 0; i <= STACK_ALIGNBYTES; i++) {
+		pthread_attr_t attr;
+
+		RZ(pthread_attr_init(&attr));
+		RZ(pthread_attr_setstack(&attr, stack, SIGSTKSZ + i));
+		RZ(pthread_create(&t, &attr, &threadspfunc, NULL));
+		RZ(pthread_attr_destroy(&attr));
+
+		alarm(1);
+		RZ(pthread_join(t, &sp));
+		alarm(0);
+
+		ATF_CHECK(sp != NULL);
+		ATF_CHECK_MSG((uintptr_t)stack <= (uintptr_t)sp &&
+		    (uintptr_t)sp <= (uintptr_t)stack + SIGSTKSZ + i,
+		    "sp=%p", sp);
+		ATF_CHECK_MSG(((uintptr_t)sp & STACK_ALIGNBYTES) == 0,
+		    "[%u] thread called with misaligned sp: %p", i, sp);
+	}
+
+	for (i = 0; i <= STACK_ALIGNBYTES; i++) {
+		pthread_attr_t attr;
+
+		RZ(pthread_attr_init(&attr));
+		RZ(pthread_attr_setstack(&attr, stack + i, SIGSTKSZ));
+		RZ(pthread_create(&t, &attr, &threadspfunc, NULL));
+		RZ(pthread_attr_destroy(&attr));
+
+		alarm(1);
+		RZ(pthread_join(t, &sp));
+		alarm(0);
+
+		ATF_CHECK(sp != NULL);
+		ATF_CHECK_MSG((uintptr_t)stack + i <= (uintptr_t)sp &&
+		    (uintptr_t)sp <= (uintptr_t)stack + i + SIGSTKSZ,
+		    "sp=%p", sp);
+		ATF_CHECK_MSG(((uintptr_t)sp & STACK_ALIGNBYTES) == 0,
+		    "[%u] thread called with misaligned sp: %p", i, sp);
+	}
+#else
+	atf_tc_skip("Not implemented on this platform");
+#endif
+}
+
+ATF_TC(misaligned_sp_and_signal);
+ATF_TC_HEAD(misaligned_sp_and_signal, tc)
+{
+	atf_tc_set_md_var(tc, "descr", "process can return from a signal"
+	    " handler even if the stack pointer is misaligned when a signal"
+	    " arrives");
+}
+ATF_TC_BODY(misaligned_sp_and_signal, tc)
+{
+#if defined STACK_ALIGNBYTES && defined HAVE_STACK_POINTER_H
+#if defined(__sh__)
+	atf_tc_expect_fail(PR_59327);
+#endif
+
+	/*
+	 * Set up a handler for SIGALRM.
+	 */
+	struct sigaction sa;
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = &signalsphandler;
+	RL(sigaction(SIGALRM, &sa, NULL));
+
+	/*
+	 * Set up an interval timer so that we receive SIGALRM after 50 ms.
+	 */
+	struct itimerval itv;
+	memset(&itv, 0, sizeof(itv));
+	itv.it_value.tv_usec = 1000 * 50;
+	RL(setitimer(ITIMER_MONOTONIC, &itv, NULL));
+
+	/*
+	 * Now misalign the SP. Wait for the signal to arrive and see what
+	 * happens. This should be fine as long as we don't use it to
+	 * access memory.
+	 */
+	MISALIGN_SP;
+	while (signalsp == NULL) {
+		/*
+		 * Make sure the compiler does not optimize this busy loop
+		 * away.
+		 */
+		__asm__("" ::: "memory");
+	}
+	/*
+	 * We could successfully return from a signal handler. Now we
+	 * should fix the SP before calling any functions.
+	 */
+	FIX_SP;
+
+	/*
+	 * But was the stack pointer aligned when we were on the signal
+	 * handler?
+	 */
+	ATF_CHECK_MSG(((uintptr_t)signalsp & STACK_ALIGNBYTES) == 0,
+	    "signal handler was called with a misaligned sp: %p",
+	    signalsp);
+#else
+	atf_tc_skip("Not implemented for this platform");
+#endif
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, contextsp);
+	ATF_TP_ADD_TC(tp, contextsplink);
+	ATF_TP_ADD_TC(tp, execsp_dynamic);
+	ATF_TP_ADD_TC(tp, execsp_static);
+	ATF_TP_ADD_TC(tp, misaligned_sp_and_signal);
+	ATF_TP_ADD_TC(tp, signalsp);
+	ATF_TP_ADD_TC(tp, signalsp_sigaltstack);
+	ATF_TP_ADD_TC(tp, threadsp);
+	return atf_no_error();
+}
diff --git a/kernel/t_time_arith.c b/kernel/t_time_arith.c
new file mode 100644
index 000000000000..0f738bfbe19a
--- /dev/null
+++ b/kernel/t_time_arith.c
@@ -0,0 +1,1224 @@
+/*	$NetBSD: t_time_arith.c,v 1.7 2025/10/06 12:05:04 riastradh Exp $	*/
+
+/*-
+ * Copyright (c) 2024-2025 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("$NetBSD: t_time_arith.c,v 1.7 2025/10/06 12:05:04 riastradh Exp $");
+
+#include <sys/timearith.h>
+
+#include <atf-c.h>
+#include <errno.h>
+#include <limits.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+#include <util.h>
+
+#include "h_macros.h"
+
+enum { HZ = 100 };
+
+int hz = HZ;
+int tick = 1000000/HZ;
+
+static sig_atomic_t jmp_en;
+static int jmp_sig;
+static jmp_buf jmp;
+
+static void
+handle_signal(int signo)
+{
+	const int errno_save = errno;
+	char buf[32];
+
+	snprintf_ss(buf, sizeof(buf), "signal %d\n", signo);
+	(void)write(STDERR_FILENO, buf, strlen(buf));
+
+	errno = errno_save;
+
+	if (jmp_en) {
+		jmp_sig = signo;
+		jmp_en = 0;
+		longjmp(jmp, 1);
+	} else {
+		raise_default_signal(signo);
+	}
+}
+
+const struct itimer_transition {
+	struct itimerspec	it_time;
+	struct timespec		it_now;
+	struct timespec		it_next;
+	int			it_overruns;
+	const char		*it_xfail;
+} itimer_transitions[] = {
+	/*
+	 * Fired more than one interval early -- treat clock as wound
+	 * backwards, not counting overruns.  Advance to the next
+	 * integral multiple of it_interval starting from it_value.
+	 */
+	[0] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {0,1}, {1,0}, 0,
+	       NULL},
+	[1] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {0,500000000}, {1,0}, 0,
+	       NULL},
+	[2] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {0,999999999}, {1,0}, 0,
+	       NULL},
+	[3] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {1,0}, {2,0}, 0,
+	       NULL},
+	[4] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {1,1}, {2,0}, 0,
+	       NULL},
+	[5] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {1,500000000}, {2,0}, 0,
+	       NULL},
+	[6] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {1,999999999}, {2,0}, 0,
+	       NULL},
+
+	/*
+	 * Fired exactly one interval early.  Treat this too as clock
+	 * wound backwards.
+	 */
+	[7] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {2,0}, {3,0}, 0,
+	       NULL},
+
+	/*
+	 * Fired less than one interval early -- callouts and real-time
+	 * clock might not be perfectly synced, counted as zero
+	 * overruns.  Advance by one interval from the scheduled time.
+	 */
+	[8] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {2,1}, {3,0}, 0,
+	       NULL},
+	[9] = {{.it_value = {3,0}, .it_interval = {1,0}},
+	       {2,500000000}, {3,0}, 0,
+	       NULL},
+	[10] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{2,999999999}, {3,0}, 0,
+		NULL},
+
+	/*
+	 * Fired exactly on time.  Advance by one interval.
+	 */
+	[11] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{3,0}, {4,0}, 0, NULL},
+
+	/*
+	 * Fired late by less than one interval -- callouts and
+	 * real-time clock might not be prefectly synced, counted as
+	 * zero overruns.  Advance by one interval from the scheduled
+	 * time (even if it's very close to a full interval).
+	 */
+	[12] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{3,1}, {4,0}, 0, NULL},
+	[14] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{3,500000000}, {4,0}, 0, NULL},
+	[15] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{3,999999999}, {4,0}, 0, NULL},
+
+	/*
+	 * Fired late by exactly one interval -- treat it as overrun.
+	 */
+	[16] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{4,0}, {5,0}, 1,
+		NULL},
+
+	/*
+	 * Fired late by more than one interval but less than two --
+	 * overrun.
+	 */
+	[17] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{4,1}, {5,0}, 1,
+		NULL},
+	[18] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{4,500000000}, {5,0}, 1,
+		NULL},
+	[19] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{4,999999999}, {5,0}, 1,
+		NULL},
+
+	/*
+	 * Fired late by exactly two intervals -- two overruns.
+	 */
+	[20] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{5,0}, {6,0}, 2,
+		NULL},
+
+	/*
+	 * Fired late by more intervals plus slop, up to 32.
+	 *
+	 * XXX Define DELAYTIMER_MAX so we can write it in terms of
+	 * that.
+	 */
+	[21] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{13,123456789}, {14,0}, 10,
+		NULL},
+	[22] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{34,999999999}, {35,0}, 31,
+		NULL},
+
+	/*
+	 * Fired late by roughly INT_MAX intervals.
+	 */
+	[23] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{(time_t)3 + INT_MAX - 1, 0},
+		{(time_t)3 + INT_MAX, 0},
+		INT_MAX - 1,
+		NULL},
+	[24] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{(time_t)3 + INT_MAX, 0},
+		{(time_t)3 + INT_MAX + 1, 0},
+		INT_MAX,
+		NULL},
+	[25] = {{.it_value = {3,0}, .it_interval = {1,0}},
+		{(time_t)3 + INT_MAX + 1, 0},
+		{(time_t)3 + INT_MAX + 2, 0},
+		INT_MAX,
+		NULL},
+
+	/* (2^63 - 1) ns */
+	[26] = {{.it_value = {3,0}, .it_interval = {9223372036,854775807}},
+		{3,1}, {9223372039,854775807}, 0, NULL},
+	/* 2^63 ns */
+	[27] = {{.it_value = {3,0}, .it_interval = {9223372036,854775808}},
+		{3,1}, {9223372039,854775808}, 0, NULL},
+	/* (2^63 + 1) ns */
+	[28] = {{.it_value = {3,0}, .it_interval = {9223372036,854775809}},
+		{3,1}, {9223372039,854775809}, 0, NULL},
+
+	/*
+	 * Overflows -- we should (XXX but currently don't) reject
+	 * intervals of at least 2^64 nanoseconds up front, since this
+	 * is more time than it is reasonable to wait (more than 584
+	 * years).
+	 */
+
+	/* (2^64 - 1) ns */
+	[29] = {{.it_value = {3,0}, .it_interval = {18446744073,709551615}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* 2^64 ns */
+	[30] = {{.it_value = {3,0}, .it_interval = {18446744073,709551616}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* (2^64 + 1) ns */
+	[31] = {{.it_value = {3,0}, .it_interval = {18446744073,709551617}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+
+	/* (2^63 - 1) us */
+	[32] = {{.it_value = {3,0}, .it_interval = {9223372036854,775807}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* 2^63 us */
+	[33] = {{.it_value = {3,0}, .it_interval = {9223372036854,775808}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* (2^63 + 1) us */
+	[34] = {{.it_value = {3,0}, .it_interval = {9223372036854,775809}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+
+	/* (2^64 - 1) us */
+	[35] = {{.it_value = {3,0}, .it_interval = {18446744073709,551615}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* 2^64 us */
+	[36] = {{.it_value = {3,0}, .it_interval = {18446744073709,551616}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* (2^64 + 1) us */
+	[37] = {{.it_value = {3,0}, .it_interval = {18446744073709,551617}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+
+	/* (2^63 - 1) ms */
+	[38] = {{.it_value = {3,0}, .it_interval = {9223372036854775,807}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* 2^63 ms */
+	[39] = {{.it_value = {3,0}, .it_interval = {9223372036854775,808}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* (2^63 + 1) ms */
+	[40] = {{.it_value = {3,0}, .it_interval = {9223372036854775,809}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+
+	/* (2^64 - 1) ms */
+	[41] = {{.it_value = {3,0}, .it_interval = {18446744073709551,615}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* 2^64 ms */
+	[42] = {{.it_value = {3,0}, .it_interval = {18446744073709551,616}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+	/* (2^64 + 1) ms */
+	[43] = {{.it_value = {3,0}, .it_interval = {18446744073709551,617}},
+		{2,999999999}, {0,0}, 0,
+		NULL},
+
+	/* invalid intervals */
+	[44] = {{.it_value = {3,0}, .it_interval = {-1,0}},
+		{3,1}, {0,0}, 0, NULL},
+	[45] = {{.it_value = {3,0}, .it_interval = {0,-1}},
+		{3,1}, {0,0}, 0, NULL},
+	[46] = {{.it_value = {3,0}, .it_interval = {0,1000000000}},
+		{3,1}, {0,0}, 0, NULL},
+
+	/*
+	 * Overflow nanosecond arithmetic.  The magic interval number
+	 * here is ceiling(INT64_MAX/2) nanoseconds.  The interval
+	 * start value will be rounded to an integral number of ticks,
+	 * so rather than write exactly `4611686018,427387905', just
+	 * round up the `now' value to the next second.  This forces an
+	 * overrun _and_ triggers int64_t arithmetic overflow.
+	 */
+	[47] = {{.it_value = {0,1},
+		 .it_interval = {4611686018,427387904}},
+		/* XXX needless overflow */
+		{4611686019,0}, {0,0}, 1,
+		NULL},
+
+	/* interval ~ 1/4 * (2^63 - 1) ns, now ~ 3/4 * (2^63 - 1) ns */
+	[48] = {{.it_value = {0,1},
+		 .it_interval = {2305843009,213693952}},
+		/* XXX needless overflow */
+		{6917529028,0}, {0,0}, 3,
+		NULL},
+	[49] = {{.it_value = {6917529027,0},
+		 .it_interval = {2305843009,213693952}},
+		{6917529028,0}, {9223372036,213693952}, 0, NULL},
+	[50] = {{.it_value = {6917529029,0},
+		 .it_interval = {2305843009,213693952}},
+		{6917529028,0}, {6917529029,0}, 0,
+		NULL},
+
+	/* interval ~ 1/2 * (2^63 - 1) ns, now ~ 3/4 * (2^63 - 1) ns */
+	[51] = {{.it_value = {0,1},
+		 .it_interval = {4611686018,427387904}},
+		/* XXX needless overflow */
+		{6917529028,0}, {0,0}, 1,
+		NULL},
+	[52] = {{.it_value = {2305843009,213693951}, /* ~1/4 * (2^63 - 1) */
+		 .it_interval = {4611686018,427387904}},
+		/* XXX needless overflow */
+		{6917529028,0}, {0,0}, 1,
+		NULL},
+	[54] = {{.it_value = {6917529027,0},
+		 .it_interval = {4611686018,427387904}},
+		{6917529028,0}, {11529215045,427387904}, 0, NULL},
+	[55] = {{.it_value = {6917529029,0},
+		 .it_interval = {4611686018,427387904}},
+		{6917529028,0}, {6917529029,0}, 0,
+		NULL},
+
+	[56] = {{.it_value = {INT64_MAX - 1,0}, .it_interval = {1,0}},
+		/* XXX needless overflow */
+		{INT64_MAX - 2,999999999}, {0,0}, 0,
+		NULL},
+	[57] = {{.it_value = {INT64_MAX - 1,0}, .it_interval = {1,0}},
+		{INT64_MAX - 1,0}, {INT64_MAX,0}, 0, NULL},
+	[58] = {{.it_value = {INT64_MAX - 1,0}, .it_interval = {1,0}},
+		{INT64_MAX - 1,1}, {INT64_MAX,0}, 0, NULL},
+	[59] = {{.it_value = {INT64_MAX - 1,0}, .it_interval = {1,0}},
+		{INT64_MAX - 1,999999999}, {INT64_MAX,0}, 0, NULL},
+	[60] = {{.it_value = {INT64_MAX - 1,0}, .it_interval = {1,0}},
+		{INT64_MAX,0}, {0,0}, 0,
+		NULL},
+	[61] = {{.it_value = {INT64_MAX - 1,0}, .it_interval = {1,0}},
+		{INT64_MAX,1}, {0,0}, 0,
+		NULL},
+	[62] = {{.it_value = {INT64_MAX - 1,0}, .it_interval = {1,0}},
+		{INT64_MAX,999999999}, {0,0}, 0,
+		NULL},
+
+	[63] = {{.it_value = {INT64_MAX,0}, .it_interval = {1,0}},
+		{INT64_MAX - 1,1}, {0,0}, 0,
+		NULL},
+	[64] = {{.it_value = {INT64_MAX,0}, .it_interval = {1,0}},
+		{INT64_MAX - 1,999999999}, {0,0}, 0,
+		NULL},
+	[65] = {{.it_value = {INT64_MAX,0}, .it_interval = {1,0}},
+		{INT64_MAX,0}, {0,0}, 0,
+		NULL},
+	[66] = {{.it_value = {INT64_MAX,0}, .it_interval = {1,0}},
+		{INT64_MAX,1}, {0,0}, 0,
+		NULL},
+	[67] = {{.it_value = {INT64_MAX,0}, .it_interval = {1,0}},
+		{INT64_MAX,999999999}, {0,0}, 0,
+		NULL},
+};
+
+ATF_TC(itimer_transitions);
+ATF_TC_HEAD(itimer_transitions, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Tests interval timer transitions");
+}
+ATF_TC_BODY(itimer_transitions, tc)
+{
+	volatile unsigned i;
+
+	REQUIRE_LIBC(signal(SIGFPE, handle_signal), SIG_ERR);
+	REQUIRE_LIBC(signal(SIGABRT, handle_signal), SIG_ERR);
+
+	for (i = 0; i < __arraycount(itimer_transitions); i++) {
+		struct itimer_transition it = itimer_transitions[i];
+		struct timespec next;
+		int overruns;
+		volatile bool aborted = true;
+		volatile bool expect_abort = false;
+
+		fprintf(stderr, "case %u\n", i);
+
+		if (it.it_xfail)
+			atf_tc_expect_fail("%s", it.it_xfail);
+
+		if (itimespecfix(&it.it_time.it_value) != 0 ||
+		    itimespecfix(&it.it_time.it_interval) != 0) {
+			fprintf(stderr, "rejected by itimerspecfix\n");
+			expect_abort = true;
+		}
+
+		if (setjmp(jmp) == 0) {
+			jmp_en = 1;
+			itimer_transition(&it.it_time, &it.it_now,
+			    &next, &overruns);
+			jmp_en = 0;
+			aborted = false;
+		}
+		ATF_CHECK(!jmp_en);
+		jmp_en = 0;	/* paranoia */
+		if (expect_abort) {
+			fprintf(stderr, "expected abort\n");
+			ATF_CHECK_MSG(aborted,
+			    "[%u] missing invariant assertion", i);
+			ATF_CHECK_MSG(jmp_sig == SIGABRT,
+			    "[%u] missing invariant assertion", i);
+		} else {
+			ATF_CHECK_MSG(!aborted, "[%u] raised signal %d: %s", i,
+			    jmp_sig, strsignal(jmp_sig));
+		}
+
+		ATF_CHECK_MSG((next.tv_sec == it.it_next.tv_sec &&
+			next.tv_nsec == it.it_next.tv_nsec),
+		    "[%u] periodic intervals of %lld.%09d from %lld.%09d"
+		    " last expired at %lld.%09d:"
+		    " next expiry at %lld.%09d, expected %lld.%09d", i,
+		    (long long)it.it_time.it_interval.tv_sec,
+		    (int)it.it_time.it_interval.tv_nsec,
+		    (long long)it.it_time.it_value.tv_sec,
+		    (int)it.it_time.it_value.tv_nsec,
+		    (long long)it.it_now.tv_sec, (int)it.it_now.tv_nsec,
+		    (long long)next.tv_sec, (int)next.tv_nsec,
+		    (long long)it.it_next.tv_sec, (int)it.it_next.tv_nsec);
+		ATF_CHECK_EQ_MSG(overruns, it.it_overruns,
+		    "[%u] periodic intervals of %lld.%09d from %lld.%09d"
+		    " last expired at %lld.%09d:"
+		    " overruns %d, expected %d", i,
+		    (long long)it.it_time.it_interval.tv_sec,
+		    (int)it.it_time.it_interval.tv_nsec,
+		    (long long)it.it_time.it_value.tv_sec,
+		    (int)it.it_time.it_value.tv_nsec,
+		    (long long)it.it_now.tv_sec, (int)it.it_now.tv_nsec,
+		    overruns, it.it_overruns);
+
+		if (it.it_xfail)
+			atf_tc_expect_pass();
+	}
+}
+
+/*
+ *                        { 0,                  if t <= 0;
+ * tstohz(t sec) @ f Hz = { ceil(t/(1/f)),      if that's below INT_MAX;
+ *                        { INT_MAX,            otherwise.
+ */
+
+#define	TSTOHZ_ROUND_XFAIL						      \
+	"PR kern/59691: tstohz(9) rounding errors"
+
+const struct tstohz_case {
+	int ts_hz;
+	struct timespec ts_ts;
+	int ts_ticks;
+	const char *ts_xfail;
+} tstohz_cases[] = {
+	/*
+	 * hz = 10
+	 */
+
+	/* negative inputs yield 0 ticks */
+	[0] = {10, {.tv_sec = -1, .tv_nsec = 0}, 0, NULL},
+	[1] = {10, {.tv_sec = -1, .tv_nsec = 999999999}, 0, NULL},
+
+	/* zero input yields 0 ticks */
+	[2] = {10, {.tv_sec = 0, .tv_nsec = 0}, 0, NULL},
+
+	/*
+	 * Nonzero input always yields >=2 ticks, because the time from
+	 * now until the next tick may be arbitrarily short, and we
+	 * need to wait one full tick, so we have to wait for two
+	 * ticks.
+	 */
+	[3] = {10, {.tv_sec = 0, .tv_nsec = 1}, 2, NULL},
+	[4] = {10, {.tv_sec = 0, .tv_nsec = 2}, 2, NULL},
+	[5] = {10, {.tv_sec = 0, .tv_nsec = 99999999}, 2, NULL},
+	[6] = {10, {.tv_sec = 0, .tv_nsec = 100000000}, 2, NULL},
+	[7] = {10, {.tv_sec = 0, .tv_nsec = 100000001}, 3, NULL},
+	[8] = {10, {.tv_sec = 0, .tv_nsec = 100000002}, 3, NULL},
+	[9] = {10, {.tv_sec = 0, .tv_nsec = 199999999}, 3, NULL},
+	[10] = {10, {.tv_sec = 0, .tv_nsec = 200000000}, 3, NULL},
+	[11] = {10, {.tv_sec = 0, .tv_nsec = 200000001}, 4, NULL},
+	[12] = {10, {.tv_sec = 0, .tv_nsec = 200000002}, 4, NULL},
+	[13] = {10, {.tv_sec = 0, .tv_nsec = 999999999}, 11, NULL},
+	[14] = {10, {.tv_sec = 1, .tv_nsec = 0}, 11, NULL},
+	[15] = {10, {.tv_sec = 1, .tv_nsec = 1}, 12, NULL},
+	[16] = {10, {.tv_sec = 1, .tv_nsec = 2}, 12, NULL},
+	/* .tv_sec ~ INT32_MAX/1000000 */
+	[17] = {10, {.tv_sec = 2147, .tv_nsec = 999999999}, 21481, NULL},
+	[18] = {10, {.tv_sec = 2148, .tv_nsec = 0}, 21481, NULL},
+	[19] = {10, {.tv_sec = 2148, .tv_nsec = 1}, 21482, NULL},
+	[20] = {10, {.tv_sec = 2148, .tv_nsec = 2}, 21482, NULL},
+	/* .tv_sec ~ INT32_MAX/hz */
+	[21] = {10, {.tv_sec = 214748364, .tv_nsec = 499999999}, 2147483646,
+		NULL},
+	/* saturate at INT_MAX = 2^31 - 1 ticks */
+	[22] = {10, {.tv_sec = 214748364, .tv_nsec = 500000000}, 2147483646,
+		NULL},
+	[23] = {10, {.tv_sec = 214748364, .tv_nsec = 500000001}, 2147483647,
+		NULL},
+	[24] = {10, {.tv_sec = 214748364, .tv_nsec = 500000002}, 2147483647,
+		NULL},
+	[25] = {10, {.tv_sec = 214748364, .tv_nsec = 599999999}, 2147483647,
+		NULL},
+	[26] = {10, {.tv_sec = 214748364, .tv_nsec = 600000000}, 2147483647,
+		NULL},
+	[27] = {10, {.tv_sec = 214748364, .tv_nsec = 999999999}, 2147483647,
+		NULL},
+	[28] = {10, {.tv_sec = 214748365, .tv_nsec = 0}, 2147483647,
+		NULL},
+	[29] = {10, {.tv_sec = 214748365, .tv_nsec = 1}, 2147483647,
+		NULL},
+	[30] = {10, {.tv_sec = 214748365, .tv_nsec = 2}, 2147483647,
+		NULL},
+	[31] = {10, {.tv_sec = (time_t)INT_MAX + 1, .tv_nsec = 123456789},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/1000000, overflows to INT_MAX ticks */
+	[32] = {10, {.tv_sec = 9223372036854, .tv_nsec = 999999999},
+		INT_MAX, NULL},
+	[33] = {10, {.tv_sec = 9223372036855, .tv_nsec = 0},
+		INT_MAX, NULL},
+	[34] = {10, {.tv_sec = 9223372036855, .tv_nsec = 1},
+		INT_MAX, NULL},
+	[35] = {10, {.tv_sec = 9223372036855, .tv_nsec = 2},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/hz, overflows to INT_MAX ticks */
+	[36] = {10, {.tv_sec = 922337203685477580, .tv_nsec = 999999999},
+		INT_MAX, NULL},
+	[37] = {10, {.tv_sec = 922337203685477581, .tv_nsec = 0},
+		INT_MAX, NULL},
+	[38] = {10, {.tv_sec = 922337203685477581, .tv_nsec = 1},
+		INT_MAX, NULL},
+	[39] = {10, {.tv_sec = 922337203685477581, .tv_nsec = 2},
+		INT_MAX, NULL},
+	[40] = {10, {.tv_sec = (time_t)INT_MAX + 1, .tv_nsec = 123456789},
+		INT_MAX, NULL},
+
+	/*
+	 * hz = 100
+	 */
+
+	[41] = {100, {.tv_sec = -1, .tv_nsec = 0}, 0, NULL},
+	[42] = {100, {.tv_sec = -1, .tv_nsec = 999999999}, 0, NULL},
+	[43] = {100, {.tv_sec = 0, .tv_nsec = 0}, 0, NULL},
+	[44] = {100, {.tv_sec = 0, .tv_nsec = 1}, 2, NULL},
+	[45] = {100, {.tv_sec = 0, .tv_nsec = 2}, 2, NULL},
+	[46] = {100, {.tv_sec = 0, .tv_nsec = 9999999}, 2, NULL},
+	[47] = {100, {.tv_sec = 0, .tv_nsec = 10000000}, 2, NULL},
+	[48] = {100, {.tv_sec = 0, .tv_nsec = 10000001}, 3, NULL},
+	[49] = {100, {.tv_sec = 0, .tv_nsec = 10000002}, 3, NULL},
+	[50] = {100, {.tv_sec = 0, .tv_nsec = 19999999}, 3, NULL},
+	[51] = {100, {.tv_sec = 0, .tv_nsec = 20000000}, 3, NULL},
+	[52] = {100, {.tv_sec = 0, .tv_nsec = 20000001}, 4, NULL},
+	[53] = {100, {.tv_sec = 0, .tv_nsec = 20000002}, 4, NULL},
+	[54] = {100, {.tv_sec = 0, .tv_nsec = 99999999}, 11, NULL},
+	[55] = {100, {.tv_sec = 0, .tv_nsec = 100000000}, 11, NULL},
+	[56] = {100, {.tv_sec = 0, .tv_nsec = 100000001}, 12, NULL},
+	[57] = {100, {.tv_sec = 0, .tv_nsec = 100000002}, 12, NULL},
+	[58] = {100, {.tv_sec = 0, .tv_nsec = 999999999}, 101, NULL},
+	[59] = {100, {.tv_sec = 1, .tv_nsec = 0}, 101, NULL},
+	[60] = {100, {.tv_sec = 1, .tv_nsec = 1}, 102, NULL},
+	[61] = {100, {.tv_sec = 1, .tv_nsec = 2}, 102, NULL},
+	/* .tv_sec ~ INT32_MAX/1000000 */
+	[62] = {100, {.tv_sec = 2147, .tv_nsec = 999999999}, 214801, NULL},
+	[63] = {100, {.tv_sec = 2148, .tv_nsec = 0}, 214801, NULL},
+	[64] = {100, {.tv_sec = 2148, .tv_nsec = 1}, 214802, NULL},
+	[65] = {100, {.tv_sec = 2148, .tv_nsec = 2}, 214802, NULL},
+	/* .tv_sec ~ INT32_MAX/hz */
+	[66] = {100, {.tv_sec = 21474836, .tv_nsec = 439999999}, 2147483645,
+		NULL},
+	[67] = {100, {.tv_sec = 21474836, .tv_nsec = 440000000}, 2147483645,
+		NULL},
+	[68] = {100, {.tv_sec = 21474836, .tv_nsec = 440000001}, 2147483646,
+		NULL},
+	[69] = {100, {.tv_sec = 21474836, .tv_nsec = 440000002}, 2147483646,
+		NULL},
+	[70] = {100, {.tv_sec = 21474836, .tv_nsec = 449999999}, 2147483646,
+		NULL},
+	[71] = {100, {.tv_sec = 21474836, .tv_nsec = 450000000}, 2147483646,
+		NULL},
+	/* saturate at INT_MAX = 2^31 - 1 ticks */
+	[72] = {100, {.tv_sec = 21474836, .tv_nsec = 450000001}, 2147483647,
+		NULL},
+	[73] = {100, {.tv_sec = 21474836, .tv_nsec = 450000002}, 2147483647,
+		NULL},
+	[74] = {100, {.tv_sec = 21474836, .tv_nsec = 459999999}, 2147483647,
+		NULL},
+	[75] = {100, {.tv_sec = 21474836, .tv_nsec = 460000000}, 2147483647,
+		NULL},
+	[76] = {100, {.tv_sec = 21474836, .tv_nsec = 460000001}, 2147483647,
+		NULL},
+	[77] = {100, {.tv_sec = 21474836, .tv_nsec = 460000002}, 2147483647,
+		NULL},
+	[78] = {100, {.tv_sec = 21474836, .tv_nsec = 999999999}, 2147483647,
+		NULL},
+	[79] = {100, {.tv_sec = 21474837, .tv_nsec = 0}, 2147483647,
+		NULL},
+	[80] = {100, {.tv_sec = 21474837, .tv_nsec = 1}, 2147483647,
+		NULL},
+	[81] = {100, {.tv_sec = 21474837, .tv_nsec = 2}, 2147483647,
+		NULL},
+	[82] = {100, {.tv_sec = 21474837, .tv_nsec = 2}, 2147483647,
+		NULL},
+	/* .tv_sec ~ INT64_MAX/1000000 */
+	[83] = {100, {.tv_sec = 9223372036854, .tv_nsec = 999999999},
+		INT_MAX, NULL},
+	[84] = {100, {.tv_sec = 9223372036855, .tv_nsec = 0},
+		INT_MAX, NULL},
+	[85] = {100, {.tv_sec = 9223372036855, .tv_nsec = 1},
+		INT_MAX, NULL},
+	[86] = {100, {.tv_sec = 9223372036855, .tv_nsec = 2},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/hz, overflows to INT_MAX ticks */
+	[87] = {100, {.tv_sec = 92233720368547758, .tv_nsec = 999999999},
+		INT_MAX, NULL},
+	[88] = {100, {.tv_sec = 92233720368547758, .tv_nsec = 0},
+		INT_MAX, NULL},
+	[89] = {100, {.tv_sec = 92233720368547758, .tv_nsec = 1},
+		INT_MAX, NULL},
+	[90] = {100, {.tv_sec = 92233720368547758, .tv_nsec = 2},
+		INT_MAX, NULL},
+	[91] = {100, {.tv_sec = (time_t)INT_MAX + 1, .tv_nsec = 123456789},
+		INT_MAX, NULL},
+
+	/*
+	 * hz = 1000
+	 */
+
+	[92] = {1000, {.tv_sec = -1, .tv_nsec = 0}, 0, NULL},
+	[93] = {1000, {.tv_sec = -1, .tv_nsec = 999999999}, 0, NULL},
+	[94] = {1000, {.tv_sec = 0, .tv_nsec = 0}, 0, NULL},
+	[95] = {1000, {.tv_sec = 0, .tv_nsec = 1}, 2, NULL},
+	[96] = {1000, {.tv_sec = 0, .tv_nsec = 2}, 2, NULL},
+	[97] = {1000, {.tv_sec = 0, .tv_nsec = 999999}, 2, NULL},
+	[98] = {1000, {.tv_sec = 0, .tv_nsec = 1000000}, 2, NULL},
+	[99] = {1000, {.tv_sec = 0, .tv_nsec = 1000001}, 3, NULL},
+	[100] = {1000, {.tv_sec = 0, .tv_nsec = 1000002}, 3, NULL},
+	[101] = {1000, {.tv_sec = 0, .tv_nsec = 1999999}, 3, NULL},
+	[102] = {1000, {.tv_sec = 0, .tv_nsec = 2000000}, 3, NULL},
+	[103] = {1000, {.tv_sec = 0, .tv_nsec = 2000001}, 4, NULL},
+	[104] = {1000, {.tv_sec = 0, .tv_nsec = 2000002}, 4, NULL},
+	[105] = {1000, {.tv_sec = 0, .tv_nsec = 999999999}, 1001, NULL},
+	[106] = {1000, {.tv_sec = 1, .tv_nsec = 0}, 1001, NULL},
+	[107] = {1000, {.tv_sec = 1, .tv_nsec = 1}, 1002, NULL},
+	[108] = {1000, {.tv_sec = 1, .tv_nsec = 2}, 1002, NULL},
+	/* .tv_sec ~ INT_MAX/1000000 */
+	[109] = {1000, {.tv_sec = 2147, .tv_nsec = 999999999}, 2148001, NULL},
+	[110] = {1000, {.tv_sec = 2148, .tv_nsec = 0}, 2148001, NULL},
+	[111] = {1000, {.tv_sec = 2148, .tv_nsec = 1}, 2148002, NULL},
+	[112] = {1000, {.tv_sec = 2148, .tv_nsec = 2}, 2148002, NULL},
+	/* .tv_sec ~ INT_MAX/hz */
+	[113] = {1000, {.tv_sec = 2147483, .tv_nsec = 643999999}, 2147483645,
+		NULL},
+	[114] = {1000, {.tv_sec = 2147483, .tv_nsec = 644000000}, 2147483645,
+		NULL},
+	[115] = {1000, {.tv_sec = 2147483, .tv_nsec = 644000001}, 2147483646,
+		NULL},
+	[116] = {1000, {.tv_sec = 2147483, .tv_nsec = 644000002}, 2147483646,
+		NULL},
+	[117] = {1000, {.tv_sec = 2147483, .tv_nsec = 644999999}, 2147483646,
+		NULL},
+	[118] = {1000, {.tv_sec = 2147483, .tv_nsec = 645000000}, 2147483646,
+		NULL},
+	/* saturate at INT_MAX = 2^31 - 1 ticks */
+	[119] = {1000, {.tv_sec = 2147483, .tv_nsec = 645000001}, 2147483647,
+		NULL},
+	[120] = {1000, {.tv_sec = 2147483, .tv_nsec = 645000002}, 2147483647,
+		NULL},
+	[121] = {1000, {.tv_sec = 2147483, .tv_nsec = 645999999}, 2147483647,
+		NULL},
+	[122] = {1000, {.tv_sec = 2147483, .tv_nsec = 646000000}, 2147483647,
+		NULL},
+	[123] = {1000, {.tv_sec = 2147483, .tv_nsec = 646000001}, 2147483647,
+		NULL},
+	[124] = {1000, {.tv_sec = 2147483, .tv_nsec = 646000002}, 2147483647,
+		NULL},
+	[125] = {1000, {.tv_sec = 2147483, .tv_nsec = 699999999}, 2147483647,
+		NULL},
+	[126] = {1000, {.tv_sec = 2147484, .tv_nsec = 0}, 2147483647,
+		NULL},
+	[127] = {1000, {.tv_sec = 2147484, .tv_nsec = 1}, 2147483647,
+		NULL},
+	[128] = {1000, {.tv_sec = 2147484, .tv_nsec = 2}, 2147483647,
+		NULL},
+	[129] = {1000, {.tv_sec = 2147484, .tv_nsec = 2}, 2147483647,
+		NULL},
+	/* .tv_sec ~ INT64_MAX/1000000, overflows to INT_MAX ticks */
+	[130] = {1000, {.tv_sec = 9223372036854, .tv_nsec = 999999999},
+		INT_MAX, NULL},
+	[131] = {1000, {.tv_sec = 9223372036855, .tv_nsec = 0},
+		INT_MAX, NULL},
+	[132] = {1000, {.tv_sec = 9223372036855, .tv_nsec = 1},
+		INT_MAX, NULL},
+	[133] = {1000, {.tv_sec = 9223372036855, .tv_nsec = 2},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/hz, overflows to INT_MAX ticks */
+	[134] = {1000, {.tv_sec = 92233720368547758, .tv_nsec = 999999999},
+		INT_MAX, NULL},
+	[135] = {1000, {.tv_sec = 92233720368547758, .tv_nsec = 0},
+		INT_MAX, NULL},
+	[136] = {1000, {.tv_sec = 92233720368547758, .tv_nsec = 1},
+		INT_MAX, NULL},
+	[137] = {1000, {.tv_sec = 92233720368547758, .tv_nsec = 2},
+		INT_MAX, NULL},
+	[138] = {1000, {.tv_sec = (time_t)INT_MAX + 1, .tv_nsec = 123456789},
+		INT_MAX, NULL},
+
+	/*
+	 * hz = 8191, prime non-divisor of 10^k or 2^k
+	 */
+
+	[139] = {8191, {.tv_sec = -1, .tv_nsec = 0}, 0, NULL},
+	[140] = {8191, {.tv_sec = -1, .tv_nsec = 999999999}, 0, NULL},
+	[141] = {8191, {.tv_sec = 0, .tv_nsec = 0}, 0, NULL},
+	[142] = {8191, {.tv_sec = 0, .tv_nsec = 1}, 2, NULL},
+	[143] = {8191, {.tv_sec = 0, .tv_nsec = 2}, 2, NULL},
+	[144] = {8191, {.tv_sec = 0, .tv_nsec = 122084}, 2,
+		TSTOHZ_ROUND_XFAIL},
+	[145] = {8191, {.tv_sec = 0, .tv_nsec = 122085}, 2,
+		TSTOHZ_ROUND_XFAIL},
+	[146] = {8191, {.tv_sec = 0, .tv_nsec = 122086}, 3, NULL},
+	[147] = {8191, {.tv_sec = 0, .tv_nsec = 244168}, 3,
+		TSTOHZ_ROUND_XFAIL},
+	[148] = {8191, {.tv_sec = 0, .tv_nsec = 244169}, 3,
+		TSTOHZ_ROUND_XFAIL},
+	[149] = {8191, {.tv_sec = 0, .tv_nsec = 244170}, 3,
+		TSTOHZ_ROUND_XFAIL},
+	[150] = {8191, {.tv_sec = 0, .tv_nsec = 244171}, 4, NULL},
+	[151] = {8191, {.tv_sec = 0, .tv_nsec = 244172}, 4, NULL},
+	[152] = {8191, {.tv_sec = 0, .tv_nsec = 999999999}, 8192, NULL},
+	[153] = {8191, {.tv_sec = 1, .tv_nsec = 0}, 8192, NULL},
+	[154] = {8191, {.tv_sec = 1, .tv_nsec = 1}, 8193, NULL},
+	[155] = {8191, {.tv_sec = 1, .tv_nsec = 2}, 8193, NULL},
+	/* .tv_sec ~ INT_MAX/1000000 */
+	[156] = {8191, {.tv_sec = 2147, .tv_nsec = 999999999}, 17594269, NULL},
+	[157] = {8191, {.tv_sec = 2148, .tv_nsec = 0}, 17594269, NULL},
+	[158] = {8191, {.tv_sec = 2148, .tv_nsec = 1}, 17594270, NULL},
+	[159] = {8191, {.tv_sec = 2148, .tv_nsec = 2}, 17594270, NULL},
+	/* .tv_sec ~ INT_MAX/hz */
+	[160] = {8191, {.tv_sec = 262176, .tv_nsec = 3540471}, 2147483646,
+		NULL},
+	[161] = {8191, {.tv_sec = 262176, .tv_nsec = 3540472}, 2147483647,
+		NULL},
+	[162] = {8191, {.tv_sec = 262176, .tv_nsec = 3540473}, 2147483647,
+		NULL},
+	/* saturate at INT_MAX = 2^31 - 1 ticks */
+	[163] = {8191, {.tv_sec = 262176, .tv_nsec = 3662556}, 2147483647,
+		NULL},
+	[164] = {8191, {.tv_sec = 262176, .tv_nsec = 3662557}, 2147483647,
+		NULL},
+	[165] = {8191, {.tv_sec = 262176, .tv_nsec = 3662558}, 2147483647,
+		NULL},
+	[166] = {8191, {.tv_sec = 262176, .tv_nsec = 999999999}, 2147483647,
+		NULL},
+	/* .tv_sec ~ INT64_MAX/1000000, overflows to INT_MAX ticks */
+	[167] = {8191, {.tv_sec = 9223372036854, .tv_nsec = 999999999},
+		INT_MAX, NULL},
+	[168] = {8191, {.tv_sec = 9223372036855, .tv_nsec = 0},
+		INT_MAX, NULL},
+	[169] = {8191, {.tv_sec = 9223372036855, .tv_nsec = 1},
+		INT_MAX, NULL},
+	[170] = {8191, {.tv_sec = 9223372036855, .tv_nsec = 2},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/hz, overflows to INT_MAX ticks */
+	[171] = {8191, {.tv_sec = 92233720368547758, .tv_nsec = 999999999},
+		INT_MAX, NULL},
+	[172] = {8191, {.tv_sec = 92233720368547758, .tv_nsec = 0},
+		INT_MAX, NULL},
+	[173] = {8191, {.tv_sec = 92233720368547758, .tv_nsec = 1},
+		INT_MAX, NULL},
+	[174] = {8191, {.tv_sec = 92233720368547758, .tv_nsec = 2},
+		INT_MAX, NULL},
+	[175] = {8191, {.tv_sec = (time_t)INT_MAX + 1, .tv_nsec = 123456789},
+		INT_MAX, NULL},
+};
+
+ATF_TC(tstohz);
+ATF_TC_HEAD(tstohz, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Test tstohz(9)");
+}
+ATF_TC_BODY(tstohz, tc)
+{
+	size_t i;
+
+	for (i = 0; i < __arraycount(tstohz_cases); i++) {
+		const struct tstohz_case *ts = &tstohz_cases[i];
+		int ticks;
+
+		/* set system parameters */
+		hz = ts->ts_hz;
+		tick = 1000000/hz;
+
+		ticks = tstohz(&ts->ts_ts);
+		if (ts->ts_xfail)
+			atf_tc_expect_fail("%s", ts->ts_xfail);
+
+		/*
+		 * Allow some slop of one part per thousand in the
+		 * arithmetic, but ensure we round up, not down.
+		 */
+		ATF_CHECK_MSG(((unsigned)(ticks - ts->ts_ticks) <=
+			(unsigned)ts->ts_ticks/1000),
+		    "[%zu] tstohz(%lld.%09ld sec) @ %d Hz:"
+		    " expected %d, got %d",
+		    i,
+		    (long long)ts->ts_ts.tv_sec,
+		    (long)ts->ts_ts.tv_nsec,
+		    ts->ts_hz,
+		    ts->ts_ticks,
+		    ticks);
+		if (ts->ts_xfail)
+			atf_tc_expect_pass();
+	}
+}
+
+/*
+ *                        { 0,                  if t <= 0;
+ * tvtohz(t sec) @ f Hz = { ceil(t/(1/f)),      if that's below INT_MAX;
+ *                        { INT_MAX,            otherwise.
+ */
+
+const struct tvtohz_case {
+	int tv_hz;
+	struct timeval tv_tv;
+	int tv_ticks;
+	const char *tv_xfail;
+} tvtohz_cases[] = {
+	/*
+	 * hz = 10
+	 */
+
+	/* negative inputs yield 0 ticks */
+	[0] = {10, {.tv_sec = -1, .tv_usec = 0}, 0, NULL},
+	[1] = {10, {.tv_sec = -1, .tv_usec = 999999}, 0, NULL},
+
+	/* zero input yields 0 ticks */
+	[2] = {10, {.tv_sec = 0, .tv_usec = 0}, 0, NULL},
+
+	/*
+	 * Nonzero input always yields >=2 ticks, because the time from
+	 * now until the next tick may be arbitrarily short, and we
+	 * need to wait one full tick, so we have to wait for two
+	 * ticks.
+	 */
+	[3] = {10, {.tv_sec = 0, .tv_usec = 1}, 2, NULL},
+	[4] = {10, {.tv_sec = 0, .tv_usec = 2}, 2, NULL},
+	[5] = {10, {.tv_sec = 0, .tv_usec = 99999}, 2, NULL},
+	[6] = {10, {.tv_sec = 0, .tv_usec = 100000}, 2, NULL},
+	[7] = {10, {.tv_sec = 0, .tv_usec = 100001}, 3, NULL},
+	[8] = {10, {.tv_sec = 0, .tv_usec = 100002}, 3, NULL},
+	[9] = {10, {.tv_sec = 0, .tv_usec = 199999}, 3, NULL},
+	[10] = {10, {.tv_sec = 0, .tv_usec = 200000}, 3, NULL},
+	[11] = {10, {.tv_sec = 0, .tv_usec = 200001}, 4, NULL},
+	[12] = {10, {.tv_sec = 0, .tv_usec = 200002}, 4, NULL},
+	[13] = {10, {.tv_sec = 0, .tv_usec = 999999}, 11, NULL},
+	[14] = {10, {.tv_sec = 1, .tv_usec = 0}, 11, NULL},
+	[15] = {10, {.tv_sec = 1, .tv_usec = 1}, 12, NULL},
+	[16] = {10, {.tv_sec = 1, .tv_usec = 2}, 12, NULL},
+	/* .tv_sec ~ INT32_MAX/1000000 */
+	[17] = {10, {.tv_sec = 2147, .tv_usec = 999999}, 21481, NULL},
+	[18] = {10, {.tv_sec = 2148, .tv_usec = 0}, 21481, NULL},
+	[19] = {10, {.tv_sec = 2148, .tv_usec = 1}, 21482, NULL},
+	[20] = {10, {.tv_sec = 2148, .tv_usec = 2}, 21482, NULL},
+	/* .tv_sec ~ INT32_MAX/hz */
+	[21] = {10, {.tv_sec = 214748364, .tv_usec = 499999}, 2147483646,
+		NULL},
+	/* saturate at INT_MAX = 2^31 - 1 ticks */
+	[22] = {10, {.tv_sec = 214748364, .tv_usec = 500000}, 2147483646,
+		NULL},
+	[23] = {10, {.tv_sec = 214748364, .tv_usec = 500001}, 2147483647,
+		NULL},
+	[24] = {10, {.tv_sec = 214748364, .tv_usec = 500002}, 2147483647,
+		NULL},
+	[25] = {10, {.tv_sec = 214748364, .tv_usec = 599999}, 2147483647,
+		NULL},
+	[26] = {10, {.tv_sec = 214748364, .tv_usec = 600000}, 2147483647,
+		NULL},
+	[27] = {10, {.tv_sec = 214748364, .tv_usec = 999999}, 2147483647,
+		NULL},
+	[28] = {10, {.tv_sec = 214748365, .tv_usec = 0}, 2147483647,
+		NULL},
+	[29] = {10, {.tv_sec = 214748365, .tv_usec = 1}, 2147483647,
+		NULL},
+	[30] = {10, {.tv_sec = 214748365, .tv_usec = 2}, 2147483647,
+		NULL},
+	[31] = {10, {.tv_sec = (time_t)INT_MAX + 1, .tv_usec = 123456},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/1000000, overflows to INT_MAX ticks */
+	[32] = {10, {.tv_sec = 9223372036854, .tv_usec = 999999},
+		INT_MAX, NULL},
+	[33] = {10, {.tv_sec = 9223372036855, .tv_usec = 0},
+		INT_MAX, NULL},
+	[34] = {10, {.tv_sec = 9223372036855, .tv_usec = 1},
+		INT_MAX, NULL},
+	[35] = {10, {.tv_sec = 9223372036855, .tv_usec = 2},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/hz, overflows to INT_MAX ticks */
+	[36] = {10, {.tv_sec = 922337203685477580, .tv_usec = 999999},
+		INT_MAX, NULL},
+	[37] = {10, {.tv_sec = 922337203685477581, .tv_usec = 0},
+		INT_MAX, NULL},
+	[38] = {10, {.tv_sec = 922337203685477581, .tv_usec = 1},
+		INT_MAX, NULL},
+	[39] = {10, {.tv_sec = 922337203685477581, .tv_usec = 2},
+		INT_MAX, NULL},
+	[40] = {10, {.tv_sec = (time_t)INT_MAX + 1, .tv_usec = 123456},
+		INT_MAX, NULL},
+
+	/*
+	 * hz = 100
+	 */
+
+	[41] = {100, {.tv_sec = -1, .tv_usec = 0}, 0, NULL},
+	[42] = {100, {.tv_sec = -1, .tv_usec = 999999}, 0, NULL},
+	[43] = {100, {.tv_sec = 0, .tv_usec = 0}, 0, NULL},
+	[44] = {100, {.tv_sec = 0, .tv_usec = 1}, 2, NULL},
+	[45] = {100, {.tv_sec = 0, .tv_usec = 2}, 2, NULL},
+	[46] = {100, {.tv_sec = 0, .tv_usec = 9999}, 2, NULL},
+	[47] = {100, {.tv_sec = 0, .tv_usec = 10000}, 2, NULL},
+	[48] = {100, {.tv_sec = 0, .tv_usec = 10001}, 3, NULL},
+	[49] = {100, {.tv_sec = 0, .tv_usec = 10002}, 3, NULL},
+	[50] = {100, {.tv_sec = 0, .tv_usec = 19999}, 3, NULL},
+	[51] = {100, {.tv_sec = 0, .tv_usec = 20000}, 3, NULL},
+	[52] = {100, {.tv_sec = 0, .tv_usec = 20001}, 4, NULL},
+	[53] = {100, {.tv_sec = 0, .tv_usec = 20002}, 4, NULL},
+	[54] = {100, {.tv_sec = 0, .tv_usec = 99999}, 11, NULL},
+	[55] = {100, {.tv_sec = 0, .tv_usec = 100000}, 11, NULL},
+	[56] = {100, {.tv_sec = 0, .tv_usec = 100001}, 12, NULL},
+	[57] = {100, {.tv_sec = 0, .tv_usec = 100002}, 12, NULL},
+	[58] = {100, {.tv_sec = 0, .tv_usec = 999999}, 101, NULL},
+	[59] = {100, {.tv_sec = 1, .tv_usec = 0}, 101, NULL},
+	[60] = {100, {.tv_sec = 1, .tv_usec = 1}, 102, NULL},
+	[61] = {100, {.tv_sec = 1, .tv_usec = 2}, 102, NULL},
+	/* .tv_sec ~ INT32_MAX/1000000 */
+	[62] = {100, {.tv_sec = 2147, .tv_usec = 999999}, 214801, NULL},
+	[63] = {100, {.tv_sec = 2148, .tv_usec = 0}, 214801, NULL},
+	[64] = {100, {.tv_sec = 2148, .tv_usec = 1}, 214802, NULL},
+	[65] = {100, {.tv_sec = 2148, .tv_usec = 2}, 214802, NULL},
+	/* .tv_sec ~ INT32_MAX/hz */
+	[66] = {100, {.tv_sec = 21474836, .tv_usec = 439999}, 2147483645,
+		NULL},
+	[67] = {100, {.tv_sec = 21474836, .tv_usec = 440000}, 2147483645,
+		NULL},
+	[68] = {100, {.tv_sec = 21474836, .tv_usec = 440001}, 2147483646,
+		NULL},
+	[69] = {100, {.tv_sec = 21474836, .tv_usec = 440002}, 2147483646,
+		NULL},
+	[70] = {100, {.tv_sec = 21474836, .tv_usec = 449999}, 2147483646,
+		NULL},
+	[71] = {100, {.tv_sec = 21474836, .tv_usec = 450000}, 2147483646,
+		NULL},
+	/* saturate at INT_MAX = 2^31 - 1 ticks */
+	[72] = {100, {.tv_sec = 21474836, .tv_usec = 450001}, 2147483647,
+		NULL},
+	[73] = {100, {.tv_sec = 21474836, .tv_usec = 450002}, 2147483647,
+		NULL},
+	[74] = {100, {.tv_sec = 21474836, .tv_usec = 459999}, 2147483647,
+		NULL},
+	[75] = {100, {.tv_sec = 21474836, .tv_usec = 460000}, 2147483647,
+		NULL},
+	[76] = {100, {.tv_sec = 21474836, .tv_usec = 460001}, 2147483647,
+		NULL},
+	[77] = {100, {.tv_sec = 21474836, .tv_usec = 460002}, 2147483647,
+		NULL},
+	[78] = {100, {.tv_sec = 21474836, .tv_usec = 999999}, 2147483647,
+		NULL},
+	[79] = {100, {.tv_sec = 21474837, .tv_usec = 0}, 2147483647,
+		NULL},
+	[80] = {100, {.tv_sec = 21474837, .tv_usec = 1}, 2147483647,
+		NULL},
+	[81] = {100, {.tv_sec = 21474837, .tv_usec = 2}, 2147483647,
+		NULL},
+	[82] = {100, {.tv_sec = 21474837, .tv_usec = 2}, 2147483647,
+		NULL},
+	/* .tv_sec ~ INT64_MAX/1000000 */
+	[83] = {100, {.tv_sec = 9223372036854, .tv_usec = 999999},
+		INT_MAX, NULL},
+	[84] = {100, {.tv_sec = 9223372036855, .tv_usec = 0},
+		INT_MAX, NULL},
+	[85] = {100, {.tv_sec = 9223372036855, .tv_usec = 1},
+		INT_MAX, NULL},
+	[86] = {100, {.tv_sec = 9223372036855, .tv_usec = 2},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/hz, overflows to INT_MAX ticks */
+	[87] = {100, {.tv_sec = 92233720368547758, .tv_usec = 999999},
+		INT_MAX, NULL},
+	[88] = {100, {.tv_sec = 92233720368547758, .tv_usec = 0},
+		INT_MAX, NULL},
+	[89] = {100, {.tv_sec = 92233720368547758, .tv_usec = 1},
+		INT_MAX, NULL},
+	[90] = {100, {.tv_sec = 92233720368547758, .tv_usec = 2},
+		INT_MAX, NULL},
+	[91] = {100, {.tv_sec = (time_t)INT_MAX + 1, .tv_usec = 123456},
+		INT_MAX, NULL},
+
+	/*
+	 * hz = 1000
+	 */
+
+	[92] = {1000, {.tv_sec = -1, .tv_usec = 0}, 0, NULL},
+	[93] = {1000, {.tv_sec = -1, .tv_usec = 999999}, 0, NULL},
+	[94] = {1000, {.tv_sec = 0, .tv_usec = 0}, 0, NULL},
+	[95] = {1000, {.tv_sec = 0, .tv_usec = 1}, 2, NULL},
+	[96] = {1000, {.tv_sec = 0, .tv_usec = 2}, 2, NULL},
+	[97] = {1000, {.tv_sec = 0, .tv_usec = 999}, 2, NULL},
+	[98] = {1000, {.tv_sec = 0, .tv_usec = 1000}, 2, NULL},
+	[99] = {1000, {.tv_sec = 0, .tv_usec = 1001}, 3, NULL},
+	[100] = {1000, {.tv_sec = 0, .tv_usec = 1002}, 3, NULL},
+	[101] = {1000, {.tv_sec = 0, .tv_usec = 1999}, 3, NULL},
+	[102] = {1000, {.tv_sec = 0, .tv_usec = 2000}, 3, NULL},
+	[103] = {1000, {.tv_sec = 0, .tv_usec = 2001}, 4, NULL},
+	[104] = {1000, {.tv_sec = 0, .tv_usec = 2002}, 4, NULL},
+	[105] = {1000, {.tv_sec = 0, .tv_usec = 999999}, 1001, NULL},
+	[106] = {1000, {.tv_sec = 1, .tv_usec = 0}, 1001, NULL},
+	[107] = {1000, {.tv_sec = 1, .tv_usec = 1}, 1002, NULL},
+	[108] = {1000, {.tv_sec = 1, .tv_usec = 2}, 1002, NULL},
+	/* .tv_sec ~ INT_MAX/1000000 */
+	[109] = {1000, {.tv_sec = 2147, .tv_usec = 999999}, 2148001, NULL},
+	[110] = {1000, {.tv_sec = 2148, .tv_usec = 0}, 2148001, NULL},
+	[111] = {1000, {.tv_sec = 2148, .tv_usec = 1}, 2148002, NULL},
+	[112] = {1000, {.tv_sec = 2148, .tv_usec = 2}, 2148002, NULL},
+	/* .tv_sec ~ INT_MAX/hz */
+	[113] = {1000, {.tv_sec = 2147483, .tv_usec = 643999}, 2147483645,
+		NULL},
+	[114] = {1000, {.tv_sec = 2147483, .tv_usec = 644000}, 2147483645,
+		NULL},
+	[115] = {1000, {.tv_sec = 2147483, .tv_usec = 644001}, 2147483646,
+		NULL},
+	[116] = {1000, {.tv_sec = 2147483, .tv_usec = 644002}, 2147483646,
+		NULL},
+	[117] = {1000, {.tv_sec = 2147483, .tv_usec = 644999}, 2147483646,
+		NULL},
+	[118] = {1000, {.tv_sec = 2147483, .tv_usec = 645000}, 2147483646,
+		NULL},
+	/* saturate at INT_MAX = 2^31 - 1 ticks */
+	[119] = {1000, {.tv_sec = 2147483, .tv_usec = 645001}, 2147483647,
+		NULL},
+	[120] = {1000, {.tv_sec = 2147483, .tv_usec = 645002}, 2147483647,
+		NULL},
+	[121] = {1000, {.tv_sec = 2147483, .tv_usec = 645999}, 2147483647,
+		NULL},
+	[122] = {1000, {.tv_sec = 2147483, .tv_usec = 646000}, 2147483647,
+		NULL},
+	[123] = {1000, {.tv_sec = 2147483, .tv_usec = 646001}, 2147483647,
+		NULL},
+	[124] = {1000, {.tv_sec = 2147483, .tv_usec = 646002}, 2147483647,
+		NULL},
+	[125] = {1000, {.tv_sec = 2147483, .tv_usec = 699999}, 2147483647,
+		NULL},
+	[126] = {1000, {.tv_sec = 2147484, .tv_usec = 0}, 2147483647,
+		NULL},
+	[127] = {1000, {.tv_sec = 2147484, .tv_usec = 1}, 2147483647,
+		NULL},
+	[128] = {1000, {.tv_sec = 2147484, .tv_usec = 2}, 2147483647,
+		NULL},
+	[129] = {1000, {.tv_sec = 2147484, .tv_usec = 2}, 2147483647,
+		NULL},
+	/* .tv_sec ~ INT64_MAX/1000000, overflows to INT_MAX ticks */
+	[130] = {1000, {.tv_sec = 9223372036854, .tv_usec = 999999},
+		INT_MAX, NULL},
+	[131] = {1000, {.tv_sec = 9223372036855, .tv_usec = 0},
+		INT_MAX, NULL},
+	[132] = {1000, {.tv_sec = 9223372036855, .tv_usec = 1},
+		INT_MAX, NULL},
+	[133] = {1000, {.tv_sec = 9223372036855, .tv_usec = 2},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/hz, overflows to INT_MAX ticks */
+	[134] = {1000, {.tv_sec = 92233720368547758, .tv_usec = 999999},
+		INT_MAX, NULL},
+	[135] = {1000, {.tv_sec = 92233720368547758, .tv_usec = 0},
+		INT_MAX, NULL},
+	[136] = {1000, {.tv_sec = 92233720368547758, .tv_usec = 1},
+		INT_MAX, NULL},
+	[137] = {1000, {.tv_sec = 92233720368547758, .tv_usec = 2},
+		INT_MAX, NULL},
+	[138] = {1000, {.tv_sec = (time_t)INT_MAX + 1, .tv_usec = 123456},
+		INT_MAX, NULL},
+
+	/*
+	 * hz = 8191, prime non-divisor of 10^k or 2^k
+	 */
+
+	[139] = {8191, {.tv_sec = -1, .tv_usec = 0}, 0, NULL},
+	[140] = {8191, {.tv_sec = -1, .tv_usec = 999999}, 0, NULL},
+	[141] = {8191, {.tv_sec = 0, .tv_usec = 0}, 0, NULL},
+	[142] = {8191, {.tv_sec = 0, .tv_usec = 1}, 2, NULL},
+	[143] = {8191, {.tv_sec = 0, .tv_usec = 2}, 2, NULL},
+	[144] = {8191, {.tv_sec = 0, .tv_usec = 121}, 2, NULL},
+	[145] = {8191, {.tv_sec = 0, .tv_usec = 122}, 2, NULL},
+	[146] = {8191, {.tv_sec = 0, .tv_usec = 123}, 3, NULL},
+	[147] = {8191, {.tv_sec = 0, .tv_usec = 242}, 3, NULL},
+	[148] = {8191, {.tv_sec = 0, .tv_usec = 243}, 3, NULL},
+	[149] = {8191, {.tv_sec = 0, .tv_usec = 244}, 3, NULL},
+	[150] = {8191, {.tv_sec = 0, .tv_usec = 245}, 4, NULL},
+	[151] = {8191, {.tv_sec = 0, .tv_usec = 246}, 4, NULL},
+	[152] = {8191, {.tv_sec = 0, .tv_usec = 999999}, 8192, NULL},
+	[153] = {8191, {.tv_sec = 1, .tv_usec = 0}, 8192, NULL},
+	[154] = {8191, {.tv_sec = 1, .tv_usec = 1}, 8193, NULL},
+	[155] = {8191, {.tv_sec = 1, .tv_usec = 2}, 8193, NULL},
+	/* .tv_sec ~ INT_MAX/1000000 */
+	[156] = {8191, {.tv_sec = 2147, .tv_usec = 999999}, 17594269, NULL},
+	[157] = {8191, {.tv_sec = 2148, .tv_usec = 0}, 17594269, NULL},
+	[158] = {8191, {.tv_sec = 2148, .tv_usec = 1}, 17594270, NULL},
+	[159] = {8191, {.tv_sec = 2148, .tv_usec = 2}, 17594270, NULL},
+	/* .tv_sec ~ INT_MAX/hz */
+	[160] = {8191, {.tv_sec = 262176, .tv_usec = 3540}, 2147483646,
+		NULL},
+	[161] = {8191, {.tv_sec = 262176, .tv_usec = 3541}, 2147483647,
+		NULL},
+	[162] = {8191, {.tv_sec = 262176, .tv_usec = 3542}, 2147483647,
+		NULL},
+	/* saturate at INT_MAX = 2^31 - 1 ticks */
+	[163] = {8191, {.tv_sec = 262176, .tv_usec = 3662}, 2147483647,
+		NULL},
+	[164] = {8191, {.tv_sec = 262176, .tv_usec = 3663}, 2147483647,
+		NULL},
+	[165] = {8191, {.tv_sec = 262176, .tv_usec = 3664}, 2147483647,
+		NULL},
+	[166] = {8191, {.tv_sec = 262176, .tv_usec = 999999}, 2147483647,
+		NULL},
+	/* .tv_sec ~ INT64_MAX/1000000, overflows to INT_MAX ticks */
+	[167] = {8191, {.tv_sec = 9223372036854, .tv_usec = 999999},
+		INT_MAX, NULL},
+	[168] = {8191, {.tv_sec = 9223372036855, .tv_usec = 0},
+		INT_MAX, NULL},
+	[169] = {8191, {.tv_sec = 9223372036855, .tv_usec = 1},
+		INT_MAX, NULL},
+	[170] = {8191, {.tv_sec = 9223372036855, .tv_usec = 2},
+		INT_MAX, NULL},
+	/* .tv_sec ~ INT64_MAX/hz, overflows to INT_MAX ticks */
+	[171] = {8191, {.tv_sec = 92233720368547758, .tv_usec = 999999},
+		INT_MAX, NULL},
+	[172] = {8191, {.tv_sec = 92233720368547758, .tv_usec = 0},
+		INT_MAX, NULL},
+	[173] = {8191, {.tv_sec = 92233720368547758, .tv_usec = 1},
+		INT_MAX, NULL},
+	[174] = {8191, {.tv_sec = 92233720368547758, .tv_usec = 2},
+		INT_MAX, NULL},
+	[175] = {8191, {.tv_sec = (time_t)INT_MAX + 1, .tv_usec = 123456},
+		INT_MAX, NULL},
+};
+
+ATF_TC(tvtohz);
+ATF_TC_HEAD(tvtohz, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Test tvtohz(9)");
+}
+ATF_TC_BODY(tvtohz, tc)
+{
+	size_t i;
+
+	for (i = 0; i < __arraycount(tvtohz_cases); i++) {
+		const struct tvtohz_case *tv = &tvtohz_cases[i];
+		int ticks;
+
+		/* set system parameters */
+		hz = tv->tv_hz;
+		tick = 1000000/hz;
+
+		ticks = tvtohz(&tv->tv_tv);
+		if (tv->tv_xfail)
+			atf_tc_expect_fail("%s", tv->tv_xfail);
+
+		/*
+		 * Allow some slop of one part per thousand in the
+		 * arithmetic, but ensure we round up, not down.
+		 *
+		 * XXX Analytically determine error bounds on the
+		 * formulae we use and assess them.
+		 */
+		ATF_CHECK_MSG(((unsigned)(ticks - tv->tv_ticks) <=
+			(unsigned)tv->tv_ticks/1000),
+		    "[%zu] tvtohz(%lld.%06ld sec) @ %d Hz:"
+		    " expected %d, got %d",
+		    i,
+		    (long long)tv->tv_tv.tv_sec,
+		    (long)tv->tv_tv.tv_usec,
+		    tv->tv_hz,
+		    tv->tv_ticks,
+		    ticks);
+		if (tv->tv_xfail)
+			atf_tc_expect_pass();
+	}
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, itimer_transitions);
+	ATF_TP_ADD_TC(tp, tstohz);
+	ATF_TP_ADD_TC(tp, tvtohz);
+
+	return atf_no_error();
+}
+
diff --git a/kernel/t_unmount.c b/kernel/t_unmount.c
new file mode 100644
index 000000000000..41ed39082e61
--- /dev/null
+++ b/kernel/t_unmount.c
@@ -0,0 +1,106 @@
+/*	$NetBSD: t_unmount.c,v 1.4 2024/10/02 17:16:32 bad Exp $	*/
+
+/*-
+ * Copyright (c) 2024 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND
+ * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+ * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+ * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+ * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include <sys/cdefs.h>
+__COPYRIGHT("@(#) Copyright (c) 2024\
+ The NetBSD Foundation, inc. All rights reserved.");
+__RCSID("$NetBSD: t_unmount.c,v 1.4 2024/10/02 17:16:32 bad Exp $");
+
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <sys/vnode.h>
+
+#include <rump/rump.h>
+#include <rump/rumpvnode_if.h>
+#include <rump/rump_syscalls.h>
+
+#include <fs/tmpfs/tmpfs_args.h>
+
+#include <atf-c.h>
+#include <errno.h>
+#include <stdio.h>
+
+#include "h_macros.h"
+
+ATF_TC(async);
+ATF_TC_HEAD(async, tc)
+{
+	atf_tc_set_md_var(tc,
+	    "descr", "failed unmount of async fs should stay async");
+}
+
+#define MP "/mnt"
+
+ATF_TC_BODY(async, tc)
+{
+	struct tmpfs_args args;
+	struct vnode *vp;
+	extern struct vnode *rumpns_rootvnode;
+
+	RZ(rump_init());
+
+	memset(&args, 0, sizeof(args));
+	args.ta_version = TMPFS_ARGS_VERSION;
+	args.ta_root_mode = 0777;
+
+	/* create mount point and mount a tmpfs on it */
+	RL(rump_sys_mkdir(MP, 0777));
+	RL(rump_sys_mount(MOUNT_TMPFS, MP, MNT_ASYNC, &args, sizeof(args)));
+
+	/* make sure the tmpfs is busy */
+	RL(rump_sys_chdir(MP));
+
+	/* need a stable lwp for componentname */
+	RZ(rump_pub_lwproc_rfork(RUMP_RFCFDG));
+
+	/* get vnode of MP, unlocked */
+	RZ(rump_pub_namei(RUMP_NAMEI_LOOKUP, 0, MP, NULL, &vp, NULL));
+
+	/* make sure we didn't just get the root vnode */
+	ATF_REQUIRE_MSG((rumpns_rootvnode != vp), "drat! got the root vnode");
+
+	printf("mnt_iflag & IMNT_ONWORKLIST == %d\n",
+	    (vp->v_mount->mnt_iflag & IMNT_ONWORKLIST) != 0);
+
+	/* can't unmount a busy file system */
+	ATF_REQUIRE_ERRNO(EBUSY, rump_sys_unmount(MP, 0) == -1);
+
+	printf("mnt_iflag & IMNT_ONWORKLIST == %d\n",
+	    (vp->v_mount->mnt_iflag & IMNT_ONWORKLIST) != 0);
+
+
+	ATF_REQUIRE_MSG(((vp->v_mount->mnt_iflag & IMNT_ONWORKLIST) == 0),
+	    "mount point on syncer work list");
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, async);
+
+	return atf_no_error();
+}