aboutsummaryrefslogtreecommitdiff
path: root/arch/x86
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2014-01-11 19:15:52 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-15 15:28:53 -0800
commite23fe36a8cf5faa57d0c45868a3f7679c4f07cb0 (patch)
treed65d491b6c9f639cb6825ca44f929ef77ac0fc0f /arch/x86
parent7b2252e993e29974eb0d017156db989173ec31aa (diff)
downloadlinaro-lsk-e23fe36a8cf5faa57d0c45868a3f7679c4f07cb0.tar.gz
x86, fpu, amd: Clear exceptions in AMD FXSAVE workaround
commit 26bef1318adc1b3a530ecc807ef99346db2aa8b0 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 e25cc33ec54..e72b2e41499 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -295,12 +295,13 @@ 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);
}