[tip:x86/cpufeature] x86, cpufeature: Add cpufeature flag for SMEP

[tip-bot for Fenghua Yu <fenghua.yu@intel.com>]

Commit-ID:  d0281a257f370b09c410e466571858b4e12869c9
Gitweb:     http://git.kernel.org/tip/d0281a257f370b09c410e466571858b4e12869c9
Author:     Fenghua Yu <fenghua.yu@intel.com>
AuthorDate: Tue, 17 May 2011 18:44:26 -0700
Committer:  H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Tue, 17 May 2011 20:56:59 -0700

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>
---
 arch/x86/include/asm/cpufeature.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

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__)