2 files changed, 143 insertions, 0 deletions

diff --git a/sys/dev/random/darn.c b/sys/dev/random/darn.c
new file mode 100644
index 000000000000..e42a4287a532
--- /dev/null
+++ b/sys/dev/random/darn.c
@@ -0,0 +1,142 @@
+/*-
+ * Copyright (c) 2018 Justin Hibbits
+ * Copyright (c) 2013 The FreeBSD Foundation
+ * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
+ * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Portions of this software were developed by Konstantin Belousov
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * 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
+ *    in this position and unchanged.
+ * 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 AUTHOR ``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 AUTHOR 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>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/conf.h>
+#include <sys/lock.h>
+#include <sys/malloc.h>
+#include <sys/module.h>
+#include <sys/random.h>
+#include <sys/systm.h>
+
+#include <machine/cpu.h>
+#include <machine/md_var.h>
+
+#include <dev/random/randomdev.h>
+
+/*
+ * Power ISA 3.0 adds a "darn" instruction (Deliver A Random Number).  The RNG
+ * backing this instruction conforms to NIST SP800-90B and SP800-90C at the
+ * point of hardware design, and provides a minimum of 0.5 bits of entropy per
+ * bit.
+ */
+
+#define	RETRY_COUNT	10
+
+static u_int random_darn_read(void *, u_int);
+
+static struct random_source random_darn = {
+	.rs_ident = "PowerISA DARN random number generator",
+	.rs_source = RANDOM_PURE_DARN,
+	.rs_read = random_darn_read
+};
+
+static inline int
+darn_rng_store(u_long *buf)
+{
+	u_long rndval;
+	int retry;
+
+	for (retry = RETRY_COUNT; retry > 0; --retry) {
+		/* "DARN %rN, 1" instruction */
+		/*
+		 * Arguments for DARN: rN and "L", where "L" can be one of:
+		 * 0 - 32-bit conditional random number
+		 * 1 - Conditional random number (conditioned to remove bias)
+		 * 2 - Raw random number	 (unprocessed, may include bias)
+		 * 3 - Reserved
+		 */
+	    	__asm __volatile(".long 0x7c0105e6 | (%0 << 21)" :
+	    	    "+r"(rndval));
+		if (rndval != ~0)
+			break;
+	}
+
+	*buf = rndval;
+	return (retry);
+}
+
+/* It is required that buf length is a multiple of sizeof(u_long). */
+static u_int
+random_darn_read(void *buf, u_int c)
+{
+	u_long *b, rndval;
+	u_int count;
+
+	KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
+	b = buf;
+	for (count = c; count > 0; count -= sizeof(*b)) {
+		if (darn_rng_store(&rndval) == 0)
+			break;
+		*b++ = rndval;
+	}
+	return (c - count);
+}
+
+static int
+darn_modevent(module_t mod, int type, void *unused)
+{
+	int error = 0;
+
+	switch (type) {
+	case MOD_LOAD:
+		if (cpu_features2 & PPC_FEATURE2_DARN) {
+			random_source_register(&random_darn);
+			printf("random: fast provider: \"%s\"\n", random_darn.rs_ident);
+		}
+		break;
+
+	case MOD_UNLOAD:
+		if (cpu_features2 & PPC_FEATURE2_DARN)
+			random_source_deregister(&random_darn);
+		break;
+
+	case MOD_SHUTDOWN:
+		break;
+
+	default:
+		error = EOPNOTSUPP;
+		break;
+
+	}
+
+	return (error);
+}
+
+DEV_MODULE(darn, darn_modevent, NULL);
+MODULE_VERSION(darn, 1);
+MODULE_DEPEND(darn, random_device, 1, 1, 1);
diff --git a/sys/dev/random/random_harvestq.c b/sys/dev/random/random_harvestq.c
index f064ab02b358..4f1494f96273 100644
--- a/sys/dev/random/random_harvestq.c
+++ b/sys/dev/random/random_harvestq.c
@@ -307,6 +307,7 @@ static const char *random_source_descr[ENTROPYSOURCE] = {
 	[RANDOM_PURE_VIRTIO] = "PURE_VIRTIO",
 	[RANDOM_PURE_BROADCOM] = "PURE_BROADCOM",
 	[RANDOM_PURE_CCP] = "PURE_CCP",
+	[RANDOM_PURE_DARN] = "PURE_DARN",
 	/* "ENTROPYSOURCE" */
 };