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x86/uaccess: Remove .fixup usage

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For the !CC_AS_ASM_GOTO_OUTPUT (aka. the legacy codepath), remove the
.fixup usage by employing both EX_TYPE_EFAULT_REG and EX_FLAG_CLEAR.
Like was already done for X86_32's version of __get_user_asm_u64() use
the "a" register for output, specifically so we can use CLEAR_AX.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20211110101325.485154848@infradead.org
This commit is contained in:
Peter Zijlstra
2021-11-10 11:01:12 +01:00
parent 4c132d1d84
commit 99641e094d
1 changed files with 17 additions and 22 deletions
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39
arch/x86/include/asm/uaccess.h
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@@ -351,24 +351,22 @@ do { \
"1: movl %[lowbits],%%eax\n" \
"2: movl %[highbits],%%edx\n" \
"3:\n" \
".section .fixup,\"ax\"\n" \
"4: mov %[efault],%[errout]\n" \
" xorl %%eax,%%eax\n" \
" xorl %%edx,%%edx\n" \
" jmp 3b\n" \
".previous\n" \
_ASM_EXTABLE_UA(1b, 4b) \
_ASM_EXTABLE_UA(2b, 4b) \
_ASM_EXTABLE_TYPE_REG(1b, 3b, EX_TYPE_EFAULT_REG | \
EX_FLAG_CLEAR_AX_DX, \
%[errout]) \
_ASM_EXTABLE_TYPE_REG(2b, 3b, EX_TYPE_EFAULT_REG | \
EX_FLAG_CLEAR_AX_DX, \
%[errout]) \
: [errout] "=r" (retval), \
[output] "=&A"(x) \
: [lowbits] "m" (__m(__ptr)), \
[highbits] "m" __m(((u32 __user *)(__ptr)) + 1), \
[efault] "i" (-EFAULT), "0" (retval)); \
"0" (retval)); \
})
#else
#define __get_user_asm_u64(x, ptr, retval) \
__get_user_asm(x, ptr, retval, "q", "=r")
__get_user_asm(x, ptr, retval, "q")
#endif
#define __get_user_size(x, ptr, size, retval) \
@@ -379,14 +377,14 @@ do { \
__chk_user_ptr(ptr); \
switch (size) { \
case 1: \
__get_user_asm(x_u8__, ptr, retval, "b", "=q"); \
__get_user_asm(x_u8__, ptr, retval, "b"); \
(x) = x_u8__; \
break; \
case 2: \
__get_user_asm(x, ptr, retval, "w", "=r"); \
__get_user_asm(x, ptr, retval, "w"); \
break; \
case 4: \
__get_user_asm(x, ptr, retval, "l", "=r"); \
__get_user_asm(x, ptr, retval, "l"); \
break; \
case 8: \
__get_user_asm_u64(x, ptr, retval); \
@@ -396,20 +394,17 @@ do { \
} \
} while (0)
#define __get_user_asm(x, addr, err, itype, ltype) \
#define __get_user_asm(x, addr, err, itype) \
asm volatile("\n" \
"1: mov"itype" %[umem],%[output]\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"3: mov %[efault],%[errout]\n" \
" xorl %k[output],%k[output]\n" \
" jmp 2b\n" \
".previous\n" \
_ASM_EXTABLE_UA(1b, 3b) \
_ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG | \
EX_FLAG_CLEAR_AX, \
%[errout]) \
: [errout] "=r" (err), \
[output] ltype(x) \
[output] "=a" (x) \
: [umem] "m" (__m(addr)), \
[efault] "i" (-EFAULT), "0" (err))
"0" (err))
#endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT