From 28ebc1164a45db27261ad8440dcbe9238beaf32a Mon Sep 17 00:00:00 2001 From: Ammar Faizi Date: Sat, 24 Dec 2022 00:23:38 +0700 Subject: [PATCH] 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 Signed-off-by: Richard Weinberger Signed-off-by: Sasha Levin --- 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 2112b8d14668..ff0f3b4b6c45 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; }