[PATCH 10/22] x86,uaccess: Remove .fixup usage

Peter Zijlstra
2021-11-05T17:24:27Z

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_CLR.
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 CLR_AX.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/uaccess.h | 39 +++++++++++++++++----------------------
1 file changed, 17 insertions(+), 22 deletions(-)

--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -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