From 69b7cc1189f913a712f9fa2f1a908e5d6f2de39a Mon Sep 17 00:00:00 2001
From: markj <markj@FreeBSD.org>
Date: Fri, 10 Mar 2017 18:51:47 +0000
Subject: MFC r313841, r313850: Prevent CPU migration when checking the DTrace
 nofault flag on x86.

---
 sys/cddl/dev/dtrace/amd64/dtrace_subr.c | 11 ++++++++++-
 sys/cddl/dev/dtrace/i386/dtrace_subr.c  | 11 ++++++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

(limited to 'sys/cddl')

diff --git a/sys/cddl/dev/dtrace/amd64/dtrace_subr.c b/sys/cddl/dev/dtrace/amd64/dtrace_subr.c
index df39d2e..717f455 100644
--- a/sys/cddl/dev/dtrace/amd64/dtrace_subr.c
+++ b/sys/cddl/dev/dtrace/amd64/dtrace_subr.c
@@ -41,7 +41,9 @@
 #include <sys/dtrace_impl.h>
 #include <sys/dtrace_bsd.h>
 #include <machine/clock.h>
+#include <machine/cpufunc.h>
 #include <machine/frame.h>
+#include <machine/psl.h>
 #include <vm/pmap.h>
 
 extern void dtrace_getnanotime(struct timespec *tsp);
@@ -384,6 +386,8 @@ dtrace_gethrestime(void)
 int
 dtrace_trap(struct trapframe *frame, u_int type)
 {
+	uint16_t nofault;
+
 	/*
 	 * A trap can occur while DTrace executes a probe. Before
 	 * executing the probe, DTrace blocks re-scheduling and sets
@@ -393,7 +397,12 @@ dtrace_trap(struct trapframe *frame, u_int type)
 	 *
 	 * Check if DTrace has enabled 'no-fault' mode:
 	 */
-	if ((cpu_core[curcpu].cpuc_dtrace_flags & CPU_DTRACE_NOFAULT) != 0) {
+	sched_pin();
+	nofault = cpu_core[curcpu].cpuc_dtrace_flags & CPU_DTRACE_NOFAULT;
+	sched_unpin();
+	if (nofault) {
+		KASSERT((read_rflags() & PSL_I) == 0, ("interrupts enabled"));
+
 		/*
 		 * There are only a couple of trap types that are expected.
 		 * All the rest will be handled in the usual way.
diff --git a/sys/cddl/dev/dtrace/i386/dtrace_subr.c b/sys/cddl/dev/dtrace/i386/dtrace_subr.c
index b70eab9..3801c1b 100644
--- a/sys/cddl/dev/dtrace/i386/dtrace_subr.c
+++ b/sys/cddl/dev/dtrace/i386/dtrace_subr.c
@@ -42,7 +42,9 @@
 #include <sys/dtrace_impl.h>
 #include <sys/dtrace_bsd.h>
 #include <machine/clock.h>
+#include <machine/cpufunc.h>
 #include <machine/frame.h>
+#include <machine/psl.h>
 #include <vm/pmap.h>
 
 extern uintptr_t 	kernelbase;
@@ -386,6 +388,8 @@ dtrace_gethrestime(void)
 int
 dtrace_trap(struct trapframe *frame, u_int type)
 {
+	uint16_t nofault;
+
 	/*
 	 * A trap can occur while DTrace executes a probe. Before
 	 * executing the probe, DTrace blocks re-scheduling and sets
@@ -395,7 +399,12 @@ dtrace_trap(struct trapframe *frame, u_int type)
 	 *
 	 * Check if DTrace has enabled 'no-fault' mode:
 	 */
-	if ((cpu_core[curcpu].cpuc_dtrace_flags & CPU_DTRACE_NOFAULT) != 0) {
+	sched_pin();
+	nofault = cpu_core[curcpu].cpuc_dtrace_flags & CPU_DTRACE_NOFAULT;
+	sched_unpin();
+	if (nofault) {
+		KASSERT((read_eflags() & PSL_I) == 0, ("interrupts enabled"));
+
 		/*
 		 * There are only a couple of trap types that are expected.
 		 * All the rest will be handled in the usual way.
-- 
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