diff options
| author | H. Peter Anvin <hpa@linux.intel.com> | 2012-09-21 12:43:12 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2012-09-21 12:45:27 -0700 |
| commit | 63bcff2a307b9bcc712a8251eb27df8b2e117967 (patch) | |
| tree | 0a23a378d2c967edf63e9bb2b5df2288bf30859c /arch/x86/include/asm/fpu-internal.h | |
| parent | a052858fabb376b695f2c125633daa6728e0f284 (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/include/asm/fpu-internal.h')
| -rw-r--r-- | arch/x86/include/asm/fpu-internal.h | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h index 75f4c6d6a331..0fe13583a028 100644 --- a/arch/x86/include/asm/fpu-internal.h +++ b/arch/x86/include/asm/fpu-internal.h @@ -126,8 +126,9 @@ static inline int fxsave_user(struct i387_fxsave_struct __user *fx) /* See comment in fxsave() below. */ #ifdef CONFIG_AS_FXSAVEQ - asm volatile("1: fxsaveq %[fx]\n\t" - "2:\n" + asm volatile(ASM_STAC "\n" + "1: fxsaveq %[fx]\n\t" + "2: " ASM_CLAC "\n" ".section .fixup,\"ax\"\n" "3: movl $-1,%[err]\n" " jmp 2b\n" @@ -136,8 +137,9 @@ static inline int fxsave_user(struct i387_fxsave_struct __user *fx) : [err] "=r" (err), [fx] "=m" (*fx) : "0" (0)); #else - asm volatile("1: rex64/fxsave (%[fx])\n\t" - "2:\n" + asm volatile(ASM_STAC "\n" + "1: rex64/fxsave (%[fx])\n\t" + "2: " ASM_CLAC "\n" ".section .fixup,\"ax\"\n" "3: movl $-1,%[err]\n" " jmp 2b\n" |