x86: Introduce barrier_nospec
commit b3d7ad85b8
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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/10/head
parent
4820d42835
commit
437ac7b686
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@ -48,6 +48,10 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
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/* Override the default implementation from linux/nospec.h. */
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#define array_index_mask_nospec array_index_mask_nospec
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/* Prevent speculative execution past this barrier. */
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#define barrier_nospec() alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, \
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"lfence", X86_FEATURE_LFENCE_RDTSC)
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#ifdef CONFIG_X86_PPRO_FENCE
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#define dma_rmb() rmb()
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#else
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@ -214,8 +214,7 @@ static __always_inline unsigned long long rdtsc_ordered(void)
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* that some other imaginary CPU is updating continuously with a
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* time stamp.
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*/
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alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
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"lfence", X86_FEATURE_LFENCE_RDTSC);
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barrier_nospec();
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return rdtsc();
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}
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