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authorH. Peter Anvin <hpa@linux.intel.com>2012-09-21 12:43:12 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2012-09-21 12:45:27 -0700
commit63bcff2a307b9bcc712a8251eb27df8b2e117967 (patch)
tree0a23a378d2c967edf63e9bb2b5df2288bf30859c /arch/x86/lib/copy_user_64.S
parenta052858fabb376b695f2c125633daa6728e0f284 (diff)
x86, smap: Add STAC and CLAC instructions to control user space access
When Supervisor Mode Access Prevention (SMAP) is enabled, access to userspace from the kernel is controlled by the AC flag. To make the performance of manipulating that flag acceptable, there are two new instructions, STAC and CLAC, to set and clear it. This patch adds those instructions, via alternative(), when the SMAP feature is enabled. It also adds X86_EFLAGS_AC unconditionally to the SYSCALL entry mask; there is simply no reason to make that one conditional. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Link: http://lkml.kernel.org/r/1348256595-29119-9-git-send-email-hpa@linux.intel.com
Diffstat (limited to 'arch/x86/lib/copy_user_64.S')
-rw-r--r--arch/x86/lib/copy_user_64.S7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index 5b2995f4557a..a30ca15be21c 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -17,6 +17,7 @@
#include <asm/cpufeature.h>
#include <asm/alternative-asm.h>
#include <asm/asm.h>
+#include <asm/smap.h>
/*
* By placing feature2 after feature1 in altinstructions section, we logically
@@ -130,6 +131,7 @@ ENDPROC(bad_from_user)
*/
ENTRY(copy_user_generic_unrolled)
CFI_STARTPROC
+ ASM_STAC
cmpl $8,%edx
jb 20f /* less then 8 bytes, go to byte copy loop */
ALIGN_DESTINATION
@@ -177,6 +179,7 @@ ENTRY(copy_user_generic_unrolled)
decl %ecx
jnz 21b
23: xor %eax,%eax
+ ASM_CLAC
ret
.section .fixup,"ax"
@@ -232,6 +235,7 @@ ENDPROC(copy_user_generic_unrolled)
*/
ENTRY(copy_user_generic_string)
CFI_STARTPROC
+ ASM_STAC
andl %edx,%edx
jz 4f
cmpl $8,%edx
@@ -246,6 +250,7 @@ ENTRY(copy_user_generic_string)
3: rep
movsb
4: xorl %eax,%eax
+ ASM_CLAC
ret
.section .fixup,"ax"
@@ -273,12 +278,14 @@ ENDPROC(copy_user_generic_string)
*/
ENTRY(copy_user_enhanced_fast_string)
CFI_STARTPROC
+ ASM_STAC
andl %edx,%edx
jz 2f
movl %edx,%ecx
1: rep
movsb
2: xorl %eax,%eax
+ ASM_CLAC
ret
.section .fixup,"ax"