From: Ammar Faizi ammarfaizi2@gnuweeb.org
[ 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@gnuweeb.org Signed-off-by: Richard Weinberger richard@nod.at Signed-off-by: Sasha Levin sashal@kernel.org --- 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 891868756a51f..6d5269093f7ce 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 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 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; }