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authorLinus Torvalds <torvalds@linux-foundation.org>2014-01-11 19:15:52 -0800
committerWilly Tarreau <w@1wt.eu>2014-05-19 07:54:23 +0200
commit00659c4e9ddd25ac81c2ce1490dd0d2b12ff1f1e (patch)
tree27ea875dd14c608f4107e315592bb94062dd0622
parentb3dc3e65760a6e83e7b028d11620b9c9fa30982e (diff)
downloadlinux-linaro-stable-00659c4e9ddd25ac81c2ce1490dd0d2b12ff1f1e.tar.gz
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> (cherry picked from commit 26bef1318adc1b3a530ecc807ef99346db2aa8b0) [wt: in 2.6.32, patch applies to arch/x86/include/asm/i387.h. There's no static_cpu_has() so we use boot_cpu_has() like other kernels do with gcc3. ] Signed-off-by: Willy Tarreau <w@1wt.eu>
-rw-r--r--arch/x86/include/asm/i387.h13
1 files changed, 7 insertions, 6 deletions
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index 0b20bbb758f2..cb42fad1f6fd 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -242,12 +242,13 @@ clear_state:
/* 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. safe_address is a random variable that should be in L1 */
- alternative_input(
- GENERIC_NOP8 GENERIC_NOP2,
- "emms\n\t" /* clear stack tags */
- "fildl %[addr]", /* set F?P to defined value */
- X86_FEATURE_FXSAVE_LEAK,
- [addr] "m" (safe_address));
+ if (unlikely(boot_cpu_has(X86_FEATURE_FXSAVE_LEAK))) {
+ asm volatile(
+ "fnclex\n\t"
+ "emms\n\t"
+ "fildl %[addr]" /* set F?P to defined value */
+ : : [addr] "m" (safe_address));
+ }
end:
task_thread_info(tsk)->status &= ~TS_USEDFPU;
}