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authorLinus Torvalds <torvalds@linux-foundation.org>2014-01-11 19:15:52 -0800
committerH. Peter Anvin <hpa@zytor.com>2014-01-11 19:15:52 -0800
commit26bef1318adc1b3a530ecc807ef99346db2aa8b0 (patch)
treed7fe46fa037ee060ce9fced2ccc5014d5552f6ea /arch/x86
parent1739f09e33d8f66bf48ddbc3eca615574da6c4f6 (diff)
x86, fpu, amd: Clear exceptions in AMD FXSAVE workaround
Before we do an EMMS in the AMD FXSAVE information leak workaround we need to clear any pending exceptions, otherwise we trap with a floating-point exception inside this code. Reported-by: halfdog <me@halfdog.net> Tested-by: Borislav Petkov <bp@suse.de> Link: http://lkml.kernel.org/r/CA%2B55aFxQnY_PCG_n4=0w-VG=YLXL-yr7oMxyy0WU2gCBAf3ydg@mail.gmail.com Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/include/asm/fpu-internal.h13
1 files changed, 7 insertions, 6 deletions
diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index c49a613c645..cea1c76d49b 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -293,12 +293,13 @@ static inline int restore_fpu_checking(struct task_struct *tsk)
/* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception
is pending. Clear the x87 state here by setting it to fixed
values. "m" is a random variable that should be in L1 */
- alternative_input(
- ASM_NOP8 ASM_NOP2,
- "emms\n\t" /* clear stack tags */
- "fildl %P[addr]", /* set F?P to defined value */
- X86_FEATURE_FXSAVE_LEAK,
- [addr] "m" (tsk->thread.fpu.has_fpu));
+ if (unlikely(static_cpu_has(X86_FEATURE_FXSAVE_LEAK))) {
+ asm volatile(
+ "fnclex\n\t"
+ "emms\n\t"
+ "fildl %P[addr]" /* set F?P to defined value */
+ : : [addr] "m" (tsk->thread.fpu.has_fpu));
+ }
return fpu_restore_checking(&tsk->thread.fpu);
}