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| 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/lib/putuser.S | |
| parent | a052858fabb376b695f2c125633daa6728e0f284 (diff) | |
| download | linux-63bcff2a307b9bcc712a8251eb27df8b2e117967.tar.gz linux-63bcff2a307b9bcc712a8251eb27df8b2e117967.tar.bz2 linux-63bcff2a307b9bcc712a8251eb27df8b2e117967.zip | |
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/putuser.S')
| -rw-r--r-- | arch/x86/lib/putuser.S | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/lib/putuser.S b/arch/x86/lib/putuser.S index 7f951c8f76c4..fc6ba17a7eec 100644 --- a/arch/x86/lib/putuser.S +++ b/arch/x86/lib/putuser.S @@ -15,6 +15,7 @@ #include <asm/thread_info.h> #include <asm/errno.h> #include <asm/asm.h> +#include <asm/smap.h> /* @@ -31,7 +32,8 @@ #define ENTER CFI_STARTPROC ; \ GET_THREAD_INFO(%_ASM_BX) -#define EXIT ret ; \ +#define EXIT ASM_CLAC ; \ + ret ; \ CFI_ENDPROC .text @@ -39,6 +41,7 @@ ENTRY(__put_user_1) ENTER cmp TI_addr_limit(%_ASM_BX),%_ASM_CX jae bad_put_user + ASM_STAC 1: movb %al,(%_ASM_CX) xor %eax,%eax EXIT @@ -50,6 +53,7 @@ ENTRY(__put_user_2) sub $1,%_ASM_BX cmp %_ASM_BX,%_ASM_CX jae bad_put_user + ASM_STAC 2: movw %ax,(%_ASM_CX) xor %eax,%eax EXIT @@ -61,6 +65,7 @@ ENTRY(__put_user_4) sub $3,%_ASM_BX cmp %_ASM_BX,%_ASM_CX jae bad_put_user + ASM_STAC 3: movl %eax,(%_ASM_CX) xor %eax,%eax EXIT @@ -72,6 +77,7 @@ ENTRY(__put_user_8) sub $7,%_ASM_BX cmp %_ASM_BX,%_ASM_CX jae bad_put_user + ASM_STAC 4: mov %_ASM_AX,(%_ASM_CX) #ifdef CONFIG_X86_32 5: movl %edx,4(%_ASM_CX) |