summaryrefslogtreecommitdiffstats
path: root/arch/x86/lib/putuser.S
diff options
context:
space:
mode:
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/putuser.S
parenta052858fabb376b695f2c125633daa6728e0f284 (diff)
downloadop-kernel-dev-63bcff2a307b9bcc712a8251eb27df8b2e117967.zip
op-kernel-dev-63bcff2a307b9bcc712a8251eb27df8b2e117967.tar.gz
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 7f951c8..fc6ba17 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)
OpenPOWER on IntegriCloud