2 files changed, 24 insertions, 14 deletions

diff --git a/sys/cddl/dev/dtrace/amd64/dtrace_subr.c b/sys/cddl/dev/dtrace/amd64/dtrace_subr.c
index effcff302b3a..5338772e3ccb 100644
--- a/sys/cddl/dev/dtrace/amd64/dtrace_subr.c
+++ b/sys/cddl/dev/dtrace/amd64/dtrace_subr.c
@@ -27,6 +27,10 @@
  * Use is subject to license terms.
  */
 
+/*
+ * Copyright (c) 2011, Joyent, Inc. All rights reserved.
+ */
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/types.h>
@@ -299,14 +303,15 @@ dtrace_safe_defer_signal(void)
 	}
 
 	/*
-	 * If we've executed the original instruction, but haven't performed
-	 * the jmp back to t->t_dtrace_npc or the clean up of any registers
-	 * used to emulate %rip-relative instructions in 64-bit mode, do that
-	 * here and take the signal right away. We detect this condition by
-	 * seeing if the program counter is the range [scrpc + isz, astpc).
+	 * If we have executed the original instruction, but we have performed
+	 * neither the jmp back to t->t_dtrace_npc nor the clean up of any
+	 * registers used to emulate %rip-relative instructions in 64-bit mode,
+	 * we'll save ourselves some effort by doing that here and taking the
+	 * signal right away.  We detect this condition by seeing if the program
+	 * counter is the range [scrpc + isz, astpc).
 	 */
-	if (t->t_dtrace_astpc - rp->r_pc <
-	    t->t_dtrace_astpc - t->t_dtrace_scrpc - isz) {
+	if (rp->r_pc >= t->t_dtrace_scrpc + isz &&
+	    rp->r_pc < t->t_dtrace_astpc) {
 #ifdef __amd64
 		/*
 		 * If there is a scratch register and we're on the
diff --git a/sys/cddl/dev/dtrace/i386/dtrace_subr.c b/sys/cddl/dev/dtrace/i386/dtrace_subr.c
index 3b416f093831..6fec4f6bf094 100644
--- a/sys/cddl/dev/dtrace/i386/dtrace_subr.c
+++ b/sys/cddl/dev/dtrace/i386/dtrace_subr.c
@@ -27,6 +27,10 @@
  * Use is subject to license terms.
  */
 
+/*
+ * Copyright (c) 2011, Joyent, Inc. All rights reserved.
+ */
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/types.h>
@@ -300,14 +304,15 @@ dtrace_safe_defer_signal(void)
 	}
 
 	/*
-	 * If we've executed the original instruction, but haven't performed
-	 * the jmp back to t->t_dtrace_npc or the clean up of any registers
-	 * used to emulate %rip-relative instructions in 64-bit mode, do that
-	 * here and take the signal right away. We detect this condition by
-	 * seeing if the program counter is the range [scrpc + isz, astpc).
+	 * If we have executed the original instruction, but we have performed
+	 * neither the jmp back to t->t_dtrace_npc nor the clean up of any
+	 * registers used to emulate %rip-relative instructions in 64-bit mode,
+	 * we'll save ourselves some effort by doing that here and taking the
+	 * signal right away.  We detect this condition by seeing if the program
+	 * counter is the range [scrpc + isz, astpc).
 	 */
-	if (t->t_dtrace_astpc - rp->r_pc <
-	    t->t_dtrace_astpc - t->t_dtrace_scrpc - isz) {
+	if (rp->r_pc >= t->t_dtrace_scrpc + isz &&
+	    rp->r_pc < t->t_dtrace_astpc) {
 #ifdef __amd64
 		/*
 		 * If there is a scratch register and we're on the