From: Prarit Bhargava <prarit@redhat.com>
Date: Mon, 7 Feb 2011 14:40:16 -0500
Subject: [x86_64] vdso: fix gtod via export of sysctl_vsyscall
Message-id: <20110207144004.5565.63651.sendpatchset@prarit.bos.redhat.com>
Patchwork-id: 33095
O-Subject: [RHEL5 BZ 673616 PATCH] vdso: export sysctl_vsyscall
Bugzilla: 673616
RH-Acked-by: Amerigo Wang <amwang@redhat.com>

vdso kernel variables must be exported in vextern.h, o/w they are undefined
pointers.  In the case of calling vdso gettimeofday() in RHEL5 a missing
declaration leads to a segmentation fault.

The patch below was suggested by the reporter, and properly exports
sysctl_vsyscall which is missing from the original vdso backport.  I have
tested it on a few systems and confirmed that the patch results in a valid
gettimeofday().

Resolves BZ 673616.

P.

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/arch/x86_64/vdso/vclock_gettime.c b/arch/x86_64/vdso/vclock_gettime.c
index 5e15d01..3e586bf 100644
--- a/arch/x86_64/vdso/vclock_gettime.c
+++ b/arch/x86_64/vdso/vclock_gettime.c
@@ -105,7 +105,7 @@ static noinline int do_monotonic(struct timespec *ts)
 
 int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 {
-	if (likely(sysctl_vsyscall && (vdso_vxtime->mode != VXTIME_KVM)))
+	if (likely(vdso_sysctl_vsyscall && (vdso_vxtime->mode != VXTIME_KVM)))
 		switch (clock) {
 		case CLOCK_REALTIME:
 			return do_realtime(ts);
@@ -121,7 +121,7 @@ int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
 	long ret;
 
-	if (likely(sysctl_vsyscall && (vdso_vxtime->mode != VXTIME_KVM))) {
+	if (likely(vdso_sysctl_vsyscall && (vdso_vxtime->mode != VXTIME_KVM))) {
 		BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
 			     offsetof(struct timespec, tv_nsec) ||
 			     sizeof(*tv) != sizeof(struct timespec));
diff --git a/arch/x86_64/vdso/vextern.h b/arch/x86_64/vdso/vextern.h
index 680c7ca..8cf4051 100644
--- a/arch/x86_64/vdso/vextern.h
+++ b/arch/x86_64/vdso/vextern.h
@@ -16,3 +16,4 @@ VEXTERN(xtime_lock)
 VEXTERN(xtime)
 VEXTERN(sys_tz)
 VEXTERN(vgetcpu_mode)
+VEXTERN(sysctl_vsyscall)
diff --git a/include/asm-x86_64/vsyscall.h b/include/asm-x86_64/vsyscall.h
index dd90792..e9cb8e0 100644
--- a/include/asm-x86_64/vsyscall.h
+++ b/include/asm-x86_64/vsyscall.h
@@ -53,6 +53,7 @@ extern volatile unsigned long __jiffies;
 extern unsigned long __wall_jiffies;
 extern struct timezone __sys_tz;
 extern seqlock_t __xtime_lock;
+extern int __sysctl_vsyscall;
 
 /* kernel space (writeable) */
 extern struct vxtime_data vxtime;