[PATCH 3.18 103/120] x86/vdso: Fix vDSO syscall fallback asm constraint regression

Greg Kroah-Hartman
2018-10-11T15:40:29Z

From: Andy Lutomirski <luto@kernel.org>

commit 02e425668f5c9deb42787d10001a3b605993ad15 upstream.

When I added the missing memory outputs, I failed to update the
index of the first argument (ebx) on 32-bit builds, which broke the
fallbacks. Somehow I must have screwed up my testing or gotten
lucky.

Add another test to cover gettimeofday() as well.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: 715bd9d12f84 ("x86/vdso: Fix asm constraints on vDSO syscall fallbacks")
Link: http://lkml.kernel.org/r/21bd45ab04b6d838278fa5bebfa9163eceffa13c.1538608971.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/vdso/vclock_gettime.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -140,11 +140,11 @@ notrace static long vdso_fallback_gettim

asm (
"mov %%ebx, %%edx \n"
- "mov %2, %%ebx \n"
+ "mov %[clock], %%ebx \n"
"call __kernel_vsyscall \n"
"mov %%edx, %%ebx \n"
: "=a" (ret), "=m" (*ts)
- : "0" (__NR_clock_gettime), "g" (clock), "c" (ts)
+ : "0" (__NR_clock_gettime), [clock] "g" (clock), "c" (ts)
: "memory", "edx");
return ret;
}
@@ -155,11 +155,11 @@ notrace static long vdso_fallback_gtod(s

asm (
"mov %%ebx, %%edx \n"
- "mov %2, %%ebx \n"
+ "mov %[tv], %%ebx \n"
"call __kernel_vsyscall \n"
"mov %%edx, %%ebx \n"
: "=a" (ret), "=m" (*tv), "=m" (*tz)
- : "0" (__NR_gettimeofday), "g" (tv), "c" (tz)
+ : "0" (__NR_gettimeofday), [tv] "g" (tv), "c" (tz)
: "memory", "edx");
return ret;
}