summaryrefslogtreecommitdiffstats
path: root/arch/x86/lib/putuser.S
diff options
context:
space:
mode:
authorH. Peter Anvin <hpa@linux.intel.com>2012-09-21 21:43:12 +0200
committerH. Peter Anvin <hpa@linux.intel.com>2012-09-21 21:45:27 +0200
commit63bcff2a307b9bcc712a8251eb27df8b2e117967 (patch)
tree0a23a378d2c967edf63e9bb2b5df2288bf30859c /arch/x86/lib/putuser.S
parentx86, uaccess: Merge prototypes for clear_user/__clear_user (diff)
downloadlinux-63bcff2a307b9bcc712a8251eb27df8b2e117967.tar.xz
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.S8
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)