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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
parenta052858fabb376b695f2c125633daa6728e0f284 (diff)
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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')
-rw-r--r--arch/x86/lib/copy_user_64.S7
-rw-r--r--arch/x86/lib/copy_user_nocache_64.S3
-rw-r--r--arch/x86/lib/getuser.S10
-rw-r--r--arch/x86/lib/putuser.S8
-rw-r--r--arch/x86/lib/usercopy_32.c13
-rw-r--r--arch/x86/lib/usercopy_64.c3
6 files changed, 42 insertions, 2 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"
diff --git a/arch/x86/lib/copy_user_nocache_64.S b/arch/x86/lib/copy_user_nocache_64.S
index cacddc7163eb..6a4f43c2d9e6 100644
--- a/arch/x86/lib/copy_user_nocache_64.S
+++ b/arch/x86/lib/copy_user_nocache_64.S
@@ -15,6 +15,7 @@
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/asm.h>
+#include <asm/smap.h>
.macro ALIGN_DESTINATION
#ifdef FIX_ALIGNMENT
@@ -48,6 +49,7 @@
*/
ENTRY(__copy_user_nocache)
CFI_STARTPROC
+ ASM_STAC
cmpl $8,%edx
jb 20f /* less then 8 bytes, go to byte copy loop */
ALIGN_DESTINATION
@@ -95,6 +97,7 @@ ENTRY(__copy_user_nocache)
decl %ecx
jnz 21b
23: xorl %eax,%eax
+ ASM_CLAC
sfence
ret
diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
index b33b1fb1e6d4..156b9c804670 100644
--- a/arch/x86/lib/getuser.S
+++ b/arch/x86/lib/getuser.S
@@ -33,6 +33,7 @@
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/asm.h>
+#include <asm/smap.h>
.text
ENTRY(__get_user_1)
@@ -40,8 +41,10 @@ ENTRY(__get_user_1)
GET_THREAD_INFO(%_ASM_DX)
cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
jae bad_get_user
+ ASM_STAC
1: movzb (%_ASM_AX),%edx
xor %eax,%eax
+ ASM_CLAC
ret
CFI_ENDPROC
ENDPROC(__get_user_1)
@@ -53,8 +56,10 @@ ENTRY(__get_user_2)
GET_THREAD_INFO(%_ASM_DX)
cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
jae bad_get_user
+ ASM_STAC
2: movzwl -1(%_ASM_AX),%edx
xor %eax,%eax
+ ASM_CLAC
ret
CFI_ENDPROC
ENDPROC(__get_user_2)
@@ -66,8 +71,10 @@ ENTRY(__get_user_4)
GET_THREAD_INFO(%_ASM_DX)
cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
jae bad_get_user
+ ASM_STAC
3: mov -3(%_ASM_AX),%edx
xor %eax,%eax
+ ASM_CLAC
ret
CFI_ENDPROC
ENDPROC(__get_user_4)
@@ -80,8 +87,10 @@ ENTRY(__get_user_8)
GET_THREAD_INFO(%_ASM_DX)
cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
jae bad_get_user
+ ASM_STAC
4: movq -7(%_ASM_AX),%_ASM_DX
xor %eax,%eax
+ ASM_CLAC
ret
CFI_ENDPROC
ENDPROC(__get_user_8)
@@ -91,6 +100,7 @@ bad_get_user:
CFI_STARTPROC
xor %edx,%edx
mov $(-EFAULT),%_ASM_AX
+ ASM_CLAC
ret
CFI_ENDPROC
END(bad_get_user)
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)
diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c
index 1781b2f950e2..98f6d6b68f5a 100644
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -42,10 +42,11 @@ do { \
int __d0; \
might_fault(); \
__asm__ __volatile__( \
+ ASM_STAC "\n" \
"0: rep; stosl\n" \
" movl %2,%0\n" \
"1: rep; stosb\n" \
- "2:\n" \
+ "2: " ASM_CLAC "\n" \
".section .fixup,\"ax\"\n" \
"3: lea 0(%2,%0,4),%0\n" \
" jmp 2b\n" \
@@ -626,10 +627,12 @@ survive:
return n;
}
#endif
+ stac();
if (movsl_is_ok(to, from, n))
__copy_user(to, from, n);
else
n = __copy_user_intel(to, from, n);
+ clac();
return n;
}
EXPORT_SYMBOL(__copy_to_user_ll);
@@ -637,10 +640,12 @@ EXPORT_SYMBOL(__copy_to_user_ll);
unsigned long __copy_from_user_ll(void *to, const void __user *from,
unsigned long n)
{
+ stac();
if (movsl_is_ok(to, from, n))
__copy_user_zeroing(to, from, n);
else
n = __copy_user_zeroing_intel(to, from, n);
+ clac();
return n;
}
EXPORT_SYMBOL(__copy_from_user_ll);
@@ -648,11 +653,13 @@ EXPORT_SYMBOL(__copy_from_user_ll);
unsigned long __copy_from_user_ll_nozero(void *to, const void __user *from,
unsigned long n)
{
+ stac();
if (movsl_is_ok(to, from, n))
__copy_user(to, from, n);
else
n = __copy_user_intel((void __user *)to,
(const void *)from, n);
+ clac();
return n;
}
EXPORT_SYMBOL(__copy_from_user_ll_nozero);
@@ -660,6 +667,7 @@ EXPORT_SYMBOL(__copy_from_user_ll_nozero);
unsigned long __copy_from_user_ll_nocache(void *to, const void __user *from,
unsigned long n)
{
+ stac();
#ifdef CONFIG_X86_INTEL_USERCOPY
if (n > 64 && cpu_has_xmm2)
n = __copy_user_zeroing_intel_nocache(to, from, n);
@@ -668,6 +676,7 @@ unsigned long __copy_from_user_ll_nocache(void *to, const void __user *from,
#else
__copy_user_zeroing(to, from, n);
#endif
+ clac();
return n;
}
EXPORT_SYMBOL(__copy_from_user_ll_nocache);
@@ -675,6 +684,7 @@ EXPORT_SYMBOL(__copy_from_user_ll_nocache);
unsigned long __copy_from_user_ll_nocache_nozero(void *to, const void __user *from,
unsigned long n)
{
+ stac();
#ifdef CONFIG_X86_INTEL_USERCOPY
if (n > 64 && cpu_has_xmm2)
n = __copy_user_intel_nocache(to, from, n);
@@ -683,6 +693,7 @@ unsigned long __copy_from_user_ll_nocache_nozero(void *to, const void __user *fr
#else
__copy_user(to, from, n);
#endif
+ clac();
return n;
}
EXPORT_SYMBOL(__copy_from_user_ll_nocache_nozero);
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index e5b130bc2d0e..05928aae911e 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -18,6 +18,7 @@ unsigned long __clear_user(void __user *addr, unsigned long size)
might_fault();
/* no memory constraint because it doesn't change any memory gcc knows
about */
+ stac();
asm volatile(
" testq %[size8],%[size8]\n"
" jz 4f\n"
@@ -40,6 +41,7 @@ unsigned long __clear_user(void __user *addr, unsigned long size)
: [size8] "=&c"(size), [dst] "=&D" (__d0)
: [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr),
[zero] "r" (0UL), [eight] "r" (8UL));
+ clac();
return size;
}
EXPORT_SYMBOL(__clear_user);
@@ -82,5 +84,6 @@ copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
for (c = 0, zero_len = len; zerorest && zero_len; --zero_len)
if (__put_user_nocheck(c, to++, sizeof(char)))
break;
+ clac();
return len;
}