From: Jeff Burke <jburke@redhat.com>
Date: Mon, 20 Aug 2007 09:33:34 -0400
Subject: [x86_64] Switching to vsyscall64 causes oops
Message-id: 46C9982E.6020401@redhat.com
O-Subject: [RHEL5.2 PATCH] Bugzilla Bug 224541: oops in vsyscall_sysctl_change()
Bugzilla: 224541

Red Hat BZ#:
------
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=224541

Description:
------------
Attempt to switch vsyscall64 leads to oops in vsyscall_sysctl_change.
This patch touches two files:
 /arch/x86_64/kernel/vsyscall.c
 /arch/x86_64/kernel/vsyscall-xen.c

RHEL Version Found:
------------------
RHEL5 Beta, x86_64
2.6.23 RC3, x86_64

Upstream Status:
----------------
Original patch created by Vasily Averin <vvs@sw.ru> for RHEL5 RC1. it
was attached to the BZ. The issue _is_ in 2.6.23 RC3 and the latest
Fedora kernel also.

Test Status:
------------
This patch has been built into the RHEL5.1 2.6.18-38.el5 kernel. Tested
by me. It has also been built into the latest Fedora kernel and tested
by Jarod Wilson.

Test Case:
----------
Boot an x86_64 system with any RHEL5 kernel. Use the following commands:
 # cat /proc/sys/kernel/vsyscall64
 0
 # echo 1 > /proc/sys/kernel/vsyscall64

Actual results:
----------
Unable to handle kernel paging request at ffffc20000076c13 RIP:
 [<ffffffff80074226>] vsyscall_sysctl_change+0x9f/0xc1
PGD dfe9b067 PUD dfe9c067 PMD dfe9d067 PTE fffffffffff88163
Oops: 000b [1] SMP
last sysfs file: /class/vc/vcsa6/dev

Expected results:
----------
When switching vsyscall64 via proc or sysctl, system should _not_ oops

BREW scratch build:
-------------------
Local build, 2.6.18-38.el5.vsyscall.1

Thanks,
Jeff

Acked-by: Jarod Wilson <jwilson@redhat.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
---
 arch/x86_64/kernel/vsyscall-xen.c |    2 +-
 arch/x86_64/kernel/vsyscall.c     |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86_64/kernel/vsyscall-xen.c b/arch/x86_64/kernel/vsyscall-xen.c
index 18a5da0..0e422a2 100644
--- a/arch/x86_64/kernel/vsyscall-xen.c
+++ b/arch/x86_64/kernel/vsyscall-xen.c
@@ -45,7 +45,7 @@ seqlock_t __xtime_lock __section_xtime_lock = SEQLOCK_UNLOCKED;
 	({unsigned long v;  		\
 	extern char __vsyscall_0; 	\
 	  asm("" : "=r" (v) : "0" (x)); \
-	  ((v - VSYSCALL_FIRST_PAGE) + __pa_symbol(&__vsyscall_0)); })
+	  ((v - fix_to_virt(VSYSCALL_FIRST_PAGE)) + __pa_symbol(&__vsyscall_0)); })
 
 static __always_inline void timeval_normalize(struct timeval * tv)
 {
diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c
index 32decb0..cf6c5d1 100644
--- a/arch/x86_64/kernel/vsyscall.c
+++ b/arch/x86_64/kernel/vsyscall.c
@@ -50,7 +50,7 @@ int __vgetcpu_mode __section_vgetcpu_mode;
 	({unsigned long v;  		\
 	extern char __vsyscall_0; 	\
 	  asm("" : "=r" (v) : "0" (x)); \
-	  ((v - VSYSCALL_FIRST_PAGE) + __pa_symbol(&__vsyscall_0)); })
+	  ((v - fix_to_virt(VSYSCALL_FIRST_PAGE)) + __pa_symbol(&__vsyscall_0)); })
 
 static __always_inline void timeval_normalize(struct timeval * tv)
 {
-- 
1.5.3.5.645.gbb47