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| author | Dan Williams <dan.j.williams@intel.com> | 2018-01-29 17:02:33 -0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2018-03-19 18:58:36 +0000 |
| commit | 507089d2b9540f698a9b8648207da02edeedfcf0 (patch) | |
| tree | d79f112efe22a049f9951c780bd60695b1c0d473 | |
| parent | b75b708ffa363a3e5500fdd3f377500a2be7fd31 (diff) | |
| download | linux-stable-507089d2b9540f698a9b8648207da02edeedfcf0.tar.gz linux-stable-507089d2b9540f698a9b8648207da02edeedfcf0.tar.bz2 linux-stable-507089d2b9540f698a9b8648207da02edeedfcf0.zip | |
x86: Introduce barrier_nospec
commit b3d7ad85b80bbc404635dca80f5b129f6242bc7a upstream.
Rename the open coded form of this instruction sequence from
rdtsc_ordered() into a generic barrier primitive, barrier_nospec().
One of the mitigations for Spectre variant1 vulnerabilities is to fence
speculative execution after successfully validating a bounds check. I.e.
force the result of a bounds check to resolve in the instruction pipeline
to ensure speculative execution honors that result before potentially
operating on out-of-bounds data.
No functional changes.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Andi Kleen <ak@linux.intel.com>
Suggested-by: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: kernel-hardening@lists.openwall.com
Cc: gregkh@linuxfoundation.org
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: alan@linux.intel.com
Link: https://lkml.kernel.org/r/151727415361.33451.9049453007262764675.stgit@dwillia2-desk3.amr.corp.intel.com
[bwh: Backported to 3.2: update rdtsc_barrier() instead of rdtsc_ordered()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | arch/x86/include/asm/system.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h index 41fda4d8710c..59567d16c617 100644 --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -478,6 +478,10 @@ static inline unsigned long array_index_mask_nospec(unsigned long index, /* Override the default implementation from linux/nospec.h. */ #define array_index_mask_nospec array_index_mask_nospec +/* Prevent speculative execution past this barrier. */ +#define barrier_nospec() alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, \ + "lfence", X86_FEATURE_LFENCE_RDTSC) + /** * read_barrier_depends - Flush all pending reads that subsequents reads * depend on. @@ -563,8 +567,7 @@ static inline unsigned long array_index_mask_nospec(unsigned long index, */ static __always_inline void rdtsc_barrier(void) { - alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC); - alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC); + barrier_nospec(); } /* |