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
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 20e5f7b..9c28950 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -14,6 +14,7 @@
#include <asm/segment.h>
#include <asm/irqflags.h>
#include <asm/asm.h>
+#include <asm/smap.h>
#include <linux/linkage.h>
#include <linux/err.h>
@@ -146,8 +147,10 @@
SAVE_ARGS 0,1,0
/* no need to do an access_ok check here because rbp has been
32bit zero extended */
+ ASM_STAC
1: movl (%rbp),%ebp
_ASM_EXTABLE(1b,ia32_badarg)
+ ASM_CLAC
orl $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
CFI_REMEMBER_STATE
@@ -301,8 +304,10 @@
/* no need to do an access_ok check here because r8 has been
32bit zero extended */
/* hardware stack frame is complete now */
+ ASM_STAC
1: movl (%r8),%r9d
_ASM_EXTABLE(1b,ia32_badarg)
+ ASM_CLAC
orl $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
CFI_REMEMBER_STATE
@@ -365,6 +370,7 @@
END(ia32_cstar_target)
ia32_badarg:
+ ASM_CLAC
movq $-EFAULT,%rax
jmp ia32_sysret
CFI_ENDPROC
diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index 75f4c6d..0fe1358 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -126,8 +126,9 @@
/* 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 @@
: [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"
diff --git a/arch/x86/include/asm/futex.h b/arch/x86/include/asm/futex.h
index 71ecbcb..f373046 100644
--- a/arch/x86/include/asm/futex.h
+++ b/arch/x86/include/asm/futex.h
@@ -9,10 +9,13 @@
#include <asm/asm.h>
#include <asm/errno.h>
#include <asm/processor.h>
+#include <asm/smap.h>
#define __futex_atomic_op1(insn, ret, oldval, uaddr, oparg) \
- asm volatile("1:\t" insn "\n" \
- "2:\t.section .fixup,\"ax\"\n" \
+ asm volatile("\t" ASM_STAC "\n" \
+ "1:\t" insn "\n" \
+ "2:\t" ASM_CLAC "\n" \
+ "\t.section .fixup,\"ax\"\n" \
"3:\tmov\t%3, %1\n" \
"\tjmp\t2b\n" \
"\t.previous\n" \
@@ -21,12 +24,14 @@
: "i" (-EFAULT), "0" (oparg), "1" (0))
#define __futex_atomic_op2(insn, ret, oldval, uaddr, oparg) \
- asm volatile("1:\tmovl %2, %0\n" \
+ asm volatile("\t" ASM_STAC "\n" \
+ "1:\tmovl %2, %0\n" \
"\tmovl\t%0, %3\n" \
"\t" insn "\n" \
"2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \
"\tjnz\t1b\n" \
- "3:\t.section .fixup,\"ax\"\n" \
+ "3:\t" ASM_CLAC "\n" \
+ "\t.section .fixup,\"ax\"\n" \
"4:\tmov\t%5, %1\n" \
"\tjmp\t3b\n" \
"\t.previous\n" \
@@ -122,8 +127,10 @@
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
return -EFAULT;
- asm volatile("1:\t" LOCK_PREFIX "cmpxchgl %4, %2\n"
- "2:\t.section .fixup, \"ax\"\n"
+ asm volatile("\t" ASM_STAC "\n"
+ "1:\t" LOCK_PREFIX "cmpxchgl %4, %2\n"
+ "2:\t" ASM_CLAC "\n"
+ "\t.section .fixup, \"ax\"\n"
"3:\tmov %3, %0\n"
"\tjmp 2b\n"
"\t.previous\n"
diff --git a/arch/x86/include/asm/smap.h b/arch/x86/include/asm/smap.h
index 3989c24..8d3120f 100644
--- a/arch/x86/include/asm/smap.h
+++ b/arch/x86/include/asm/smap.h
@@ -58,13 +58,13 @@
#ifdef CONFIG_X86_SMAP
-static inline void clac(void)
+static __always_inline void clac(void)
{
/* Note: a barrier is implicit in alternative() */
alternative(ASM_NOP3, __stringify(__ASM_CLAC), X86_FEATURE_SMAP);
}
-static inline void stac(void)
+static __always_inline void stac(void)
{
/* Note: a barrier is implicit in alternative() */
alternative(ASM_NOP3, __stringify(__ASM_STAC), X86_FEATURE_SMAP);
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 2c7df3d..b92ece1 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -9,6 +9,7 @@
#include <linux/string.h>
#include <asm/asm.h>
#include <asm/page.h>
+#include <asm/smap.h>
#define VERIFY_READ 0
#define VERIFY_WRITE 1
@@ -192,9 +193,10 @@
#ifdef CONFIG_X86_32
#define __put_user_asm_u64(x, addr, err, errret) \
- asm volatile("1: movl %%eax,0(%2)\n" \
+ asm volatile(ASM_STAC "\n" \
+ "1: movl %%eax,0(%2)\n" \
"2: movl %%edx,4(%2)\n" \
- "3:\n" \
+ "3: " ASM_CLAC "\n" \
".section .fixup,\"ax\"\n" \
"4: movl %3,%0\n" \
" jmp 3b\n" \
@@ -205,9 +207,10 @@
: "A" (x), "r" (addr), "i" (errret), "0" (err))
#define __put_user_asm_ex_u64(x, addr) \
- asm volatile("1: movl %%eax,0(%1)\n" \
+ asm volatile(ASM_STAC "\n" \
+ "1: movl %%eax,0(%1)\n" \
"2: movl %%edx,4(%1)\n" \
- "3:\n" \
+ "3: " ASM_CLAC "\n" \
_ASM_EXTABLE_EX(1b, 2b) \
_ASM_EXTABLE_EX(2b, 3b) \
: : "A" (x), "r" (addr))
@@ -379,8 +382,9 @@
} while (0)
#define __get_user_asm(x, addr, err, itype, rtype, ltype, errret) \
- asm volatile("1: mov"itype" %2,%"rtype"1\n" \
- "2:\n" \
+ asm volatile(ASM_STAC "\n" \
+ "1: mov"itype" %2,%"rtype"1\n" \
+ "2: " ASM_CLAC "\n" \
".section .fixup,\"ax\"\n" \
"3: mov %3,%0\n" \
" xor"itype" %"rtype"1,%"rtype"1\n" \
@@ -412,8 +416,9 @@
} while (0)
#define __get_user_asm_ex(x, addr, itype, rtype, ltype) \
- asm volatile("1: mov"itype" %1,%"rtype"0\n" \
- "2:\n" \
+ asm volatile(ASM_STAC "\n" \
+ "1: mov"itype" %1,%"rtype"0\n" \
+ "2: " ASM_CLAC "\n" \
_ASM_EXTABLE_EX(1b, 2b) \
: ltype(x) : "m" (__m(addr)))
@@ -443,8 +448,9 @@
* aliasing issues.
*/
#define __put_user_asm(x, addr, err, itype, rtype, ltype, errret) \
- asm volatile("1: mov"itype" %"rtype"1,%2\n" \
- "2:\n" \
+ asm volatile(ASM_STAC "\n" \
+ "1: mov"itype" %"rtype"1,%2\n" \
+ "2: " ASM_CLAC "\n" \
".section .fixup,\"ax\"\n" \
"3: mov %3,%0\n" \
" jmp 2b\n" \
@@ -454,8 +460,9 @@
: ltype(x), "m" (__m(addr)), "i" (errret), "0" (err))
#define __put_user_asm_ex(x, addr, itype, rtype, ltype) \
- asm volatile("1: mov"itype" %"rtype"0,%1\n" \
- "2:\n" \
+ asm volatile(ASM_STAC "\n" \
+ "1: mov"itype" %"rtype"0,%1\n" \
+ "2: " ASM_CLAC "\n" \
_ASM_EXTABLE_EX(1b, 2b) \
: : ltype(x), "m" (__m(addr)))
diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h
index 8a1b6f9..2a923bd 100644
--- a/arch/x86/include/asm/xsave.h
+++ b/arch/x86/include/asm/xsave.h
@@ -74,8 +74,9 @@
if (unlikely(err))
return -EFAULT;
- __asm__ __volatile__("1: .byte " REX_PREFIX "0x0f,0xae,0x27\n"
- "2:\n"
+ __asm__ __volatile__(ASM_STAC "\n"
+ "1: .byte " REX_PREFIX "0x0f,0xae,0x27\n"
+ "2: " ASM_CLAC "\n"
".section .fixup,\"ax\"\n"
"3: movl $-1,%[err]\n"
" jmp 2b\n"
@@ -97,8 +98,9 @@
u32 lmask = mask;
u32 hmask = mask >> 32;
- __asm__ __volatile__("1: .byte " REX_PREFIX "0x0f,0xae,0x2f\n"
- "2:\n"
+ __asm__ __volatile__(ASM_STAC "\n"
+ "1: .byte " REX_PREFIX "0x0f,0xae,0x2f\n"
+ "2: " ASM_CLAC "\n"
".section .fixup,\"ax\"\n"
"3: movl $-1,%[err]\n"
" jmp 2b\n"
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a5fbc3c..cd43e52 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1113,7 +1113,8 @@
/* Flags to clear on syscall */
wrmsrl(MSR_SYSCALL_MASK,
- X86_EFLAGS_TF|X86_EFLAGS_DF|X86_EFLAGS_IF|X86_EFLAGS_IOPL);
+ X86_EFLAGS_TF|X86_EFLAGS_DF|X86_EFLAGS_IF|
+ X86_EFLAGS_IOPL|X86_EFLAGS_AC);
}
unsigned long kernel_eflags;
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 69babd8..ce87e3d 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -56,6 +56,7 @@
#include <asm/ftrace.h>
#include <asm/percpu.h>
#include <asm/asm.h>
+#include <asm/smap.h>
#include <linux/err.h>
/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */
@@ -465,7 +466,8 @@
* System call entry. Up to 6 arguments in registers are supported.
*
* SYSCALL does not save anything on the stack and does not change the
- * stack pointer.
+ * stack pointer. However, it does mask the flags register for us, so
+ * CLD and CLAC are not needed.
*/
/*
@@ -884,6 +886,7 @@
*/
.p2align CONFIG_X86_L1_CACHE_SHIFT
common_interrupt:
+ ASM_CLAC
XCPT_FRAME
addq $-0x80,(%rsp) /* Adjust vector to [-256,-1] range */
interrupt do_IRQ
@@ -1023,6 +1026,7 @@
*/
.macro apicinterrupt num sym do_sym
ENTRY(\sym)
+ ASM_CLAC
INTR_FRAME
pushq_cfi $~(\num)
.Lcommon_\sym:
@@ -1077,6 +1081,7 @@
*/
.macro zeroentry sym do_sym
ENTRY(\sym)
+ ASM_CLAC
INTR_FRAME
PARAVIRT_ADJUST_EXCEPTION_FRAME
pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
@@ -1094,6 +1099,7 @@
.macro paranoidzeroentry sym do_sym
ENTRY(\sym)
+ ASM_CLAC
INTR_FRAME
PARAVIRT_ADJUST_EXCEPTION_FRAME
pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
@@ -1112,6 +1118,7 @@
#define INIT_TSS_IST(x) PER_CPU_VAR(init_tss) + (TSS_ist + ((x) - 1) * 8)
.macro paranoidzeroentry_ist sym do_sym ist
ENTRY(\sym)
+ ASM_CLAC
INTR_FRAME
PARAVIRT_ADJUST_EXCEPTION_FRAME
pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
@@ -1131,6 +1138,7 @@
.macro errorentry sym do_sym
ENTRY(\sym)
+ ASM_CLAC
XCPT_FRAME
PARAVIRT_ADJUST_EXCEPTION_FRAME
subq $ORIG_RAX-R15, %rsp
@@ -1149,6 +1157,7 @@
/* error code is on the stack already */
.macro paranoiderrorentry sym do_sym
ENTRY(\sym)
+ ASM_CLAC
XCPT_FRAME
PARAVIRT_ADJUST_EXCEPTION_FRAME
subq $ORIG_RAX-R15, %rsp
diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index 5b2995f..a30ca15 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 @@
*/
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 @@
decl %ecx
jnz 21b
23: xor %eax,%eax
+ ASM_CLAC
ret
.section .fixup,"ax"
@@ -232,6 +235,7 @@
*/
ENTRY(copy_user_generic_string)
CFI_STARTPROC
+ ASM_STAC
andl %edx,%edx
jz 4f
cmpl $8,%edx
@@ -246,6 +250,7 @@
3: rep
movsb
4: xorl %eax,%eax
+ ASM_CLAC
ret
.section .fixup,"ax"
@@ -273,12 +278,14 @@
*/
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 cacddc7..6a4f43c 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 @@
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 b33b1fb..156b9c8 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 @@
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 @@
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 @@
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 @@
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 @@
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 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 @@
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 @@
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 @@
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 @@
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 1781b2f..98f6d6b6 100644
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -42,10 +42,11 @@
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 @@
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 @@
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 @@
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 @@
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 @@
#else
__copy_user_zeroing(to, from, n);
#endif
+ clac();
return n;
}
EXPORT_SYMBOL(__copy_from_user_ll_nocache);
@@ -675,6 +684,7 @@
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 @@
#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 e5b130b..05928aa 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -18,6 +18,7 @@
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 @@
: [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 @@
for (c = 0, zero_len = len; zerorest && zero_len; --zero_len)
if (__put_user_nocheck(c, to++, sizeof(char)))
break;
+ clac();
return len;
}