This is a note to let you know that I've just added the patch titled
x86: um: vdso: Add '%rcx' and '%r11' to the syscall clobber list
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-um-vdso-add-rcx-and-r11-to-the-syscall-clobber-l.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 78786ad050dbc6d0ac3ca514bfe9a8e97b372abb
Author: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
Date: Sat Dec 24 00:23:38 2022 +0700
x86: um: vdso: Add '%rcx' and '%r11' to the syscall clobber list
[ Upstream commit 5541992e512de8c9133110809f767bd1b54ee10d ]
The 'syscall' instruction clobbers '%rcx' and '%r11', but they are not
listed in the inline Assembly that performs the syscall instruction.
No real bug is found. It wasn't buggy by luck because '%rcx' and '%r11'
are caller-saved registers, and not used in the functions, and the
functions are never inlined.
Add them to the clobber list for code correctness.
Fixes: f1c2bb8b9964ed31de988910f8b1cfb586d30091 ("um: implement a x86_64 vDSO")
Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
Signed-off-by: Richard Weinberger <richard@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/um/vdso/um_vdso.c b/arch/x86/um/vdso/um_vdso.c
index 2112b8d146688..ff0f3b4b6c45e 100644
--- a/arch/x86/um/vdso/um_vdso.c
+++ b/arch/x86/um/vdso/um_vdso.c
@@ -17,8 +17,10 @@ int __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
{
long ret;
- asm("syscall" : "=a" (ret) :
- "0" (__NR_clock_gettime), "D" (clock), "S" (ts) : "memory");
+ asm("syscall"
+ : "=a" (ret)
+ : "0" (__NR_clock_gettime), "D" (clock), "S" (ts)
+ : "rcx", "r11", "memory");
return ret;
}
@@ -29,8 +31,10 @@ int __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
{
long ret;
- asm("syscall" : "=a" (ret) :
- "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
+ asm("syscall"
+ : "=a" (ret)
+ : "0" (__NR_gettimeofday), "D" (tv), "S" (tz)
+ : "rcx", "r11", "memory");
return ret;
}
