3.2.55-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Linus Torvalds <torva...@linux-foundation.org> 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 <m...@halfdog.net> Tested-by: Borislav Petkov <b...@suse.de> Link: http://lkml.kernel.org/r/CA%2B55aFxQnY_PCG_n4=0w-VG=ylxl-yr7omxyy0wu2gcbaf3...@mail.gmail.com Signed-off-by: H. Peter Anvin <h...@zytor.com> [bwh: Backported to 3.2: adjust filename, context] Signed-off-by: Ben Hutchings <b...@decadent.org.uk> --- arch/x86/kernel/traps.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -582,12 +582,13 @@ void __math_state_restore(struct task_st /* 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( - 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" (safe_address)); + 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" (safe_address)); + } /* * Paranoid restore. send a SIGSEGV if we fail to restore the state. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
