From: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
[ 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>
---
arch/x86/um/vdso/um_vdso.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
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;
}
--
2.39.2
