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x86: um: vdso: Add '%rcx' and '%r11' to the syscall clobber list 

[ Upstream commit 5541992e51 ]

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: f1c2bb8b99 ("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>
This commit is contained in:
Ammar Faizi 2022-12-24 00:23:38 +07:00 committed by Greg Kroah-Hartman
parent 44b713a242
commit 28ebc1164a
1 changed files with 8 additions and 4 deletions
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12
arch/x86/um/vdso/um_vdso.c
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@ -17,8 +17,10 @@ int __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
{ {
long ret; long ret;
asm("syscall" : "=a" (ret) : asm("syscall"
"0" (__NR_clock_gettime), "D" (clock), "S" (ts) : "memory"); : "=a" (ret)
: "0" (__NR_clock_gettime), "D" (clock), "S" (ts)
: "rcx", "r11", "memory");
return ret; return ret;
} }
@ -29,8 +31,10 @@ int __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
{ {
long ret; long ret;
asm("syscall" : "=a" (ret) : asm("syscall"
"0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory"); : "=a" (ret)
: "0" (__NR_gettimeofday), "D" (tv), "S" (tz)
: "rcx", "r11", "memory");
return ret; return ret;
} }