x86, cpufeature: Add cpufeature flag for SMEP
Add support for newly documented SMEP (Supervisor Mode Execution Protection) CPU
feature flag.
SMEP prevents the CPU in kernel-mode to jump to an executable page
that has the user flag set in the PTE. This prevents the kernel from
executing user-space code accidentally or maliciously, so it for
example prevents kernel exploits from jumping to specially prepared
user-mode shell code.
[ hpa: added better description by Ingo Molnar ]
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
LKML-Reference: <1305683069-25394-2-git-send-email-fenghua.yu@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 7f2f7b1..8808cdb 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -195,6 +195,7 @@
/* Intel-defined CPU features, CPUID level 0x00000007:0 (ebx), word 9 */
#define X86_FEATURE_FSGSBASE (9*32+ 0) /* {RD/WR}{FS/GS}BASE instructions*/
+#define X86_FEATURE_SMEP (9*32+ 7) /* Supervisor Mode Execution Protection */
#define X86_FEATURE_ERMS (9*32+ 9) /* Enhanced REP MOVSB/STOSB */
#if defined(__KERNEL__) && !defined(__ASSEMBLY__)