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xtensa: fix type conversion in __get_user_[no]check 

__get_user_[no]check uses temporary buffer of type long to store result
of __get_user_size and do sign extension on it when necessary. This
doesn't work correctly for 64-bit data. Fix it by moving temporary
buffer/sign extension logic to __get_user_asm.

Don't do assignment of __get_user_bad result to (x) as it may not always
be integer-compatible now and issue warning even when it's going to be
optimized. Instead do (x) = 0; and call __get_user_bad separately.

Zero initialize __x in __get_user_asm and use '+' constraint for its
assembly argument, so that its value is preserved in error cases. This
may add at most 1 cycle to the fast path, but saves an instruction and
two padding bytes in the fixup section for each use of this macro and
works for both misaligned store and store exception.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
This commit is contained in:
Max Filippov 2019-10-10 20:55:35 -07:00
parent c043764296
commit c9c63f3c7a
1 changed files with 29 additions and 26 deletions
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55
arch/xtensa/include/asm/uaccess.h
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@ -172,19 +172,19 @@ __asm__ __volatile__( \
#define __get_user_nocheck(x, ptr, size) \ #define __get_user_nocheck(x, ptr, size) \
({ \ ({ \
long __gu_err, __gu_val; \ long __gu_err; \
__get_user_size(__gu_val, (ptr), (size), __gu_err); \ __get_user_size((x), (ptr), (size), __gu_err); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
__gu_err; \ __gu_err; \
}) })
#define __get_user_check(x, ptr, size) \ #define __get_user_check(x, ptr, size) \
({ \ ({ \
long __gu_err = -EFAULT, __gu_val = 0; \ long __gu_err = -EFAULT; \
const __typeof__(*(ptr)) *__gu_addr = (ptr); \ const __typeof__(*(ptr)) *__gu_addr = (ptr); \
if (access_ok(__gu_addr, size)) \ if (access_ok(__gu_addr, size)) \
__get_user_size(__gu_val, __gu_addr, (size), __gu_err); \ __get_user_size((x), __gu_addr, (size), __gu_err); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \ else \
(x) = 0; \
__gu_err; \ __gu_err; \
}) })
@ -208,7 +208,7 @@ do { \
} \ } \
break; \ break; \
} \ } \
default: (x) = __get_user_bad(); \ default: (x) = 0; __get_user_bad(); \
} \ } \
} while (0) } while (0)
@ -218,24 +218,27 @@ do { \
* __check_align_* macros still work. * __check_align_* macros still work.
*/ */
#define __get_user_asm(x_, addr_, err_, align, insn, cb) \ #define __get_user_asm(x_, addr_, err_, align, insn, cb) \
__asm__ __volatile__( \ do { \
__check_align_##align \ u32 __x = 0; \
"1: "insn" %[x], %[addr], 0 \n" \ __asm__ __volatile__( \
"2: \n" \ __check_align_##align \
" .section .fixup,\"ax\" \n" \ "1: "insn" %[x], %[addr], 0 \n" \
" .align 4 \n" \ "2: \n" \
" .literal_position \n" \ " .section .fixup,\"ax\" \n" \
"5: \n" \ " .align 4 \n" \
" movi %[tmp], 2b \n" \ " .literal_position \n" \
" movi %[x], 0 \n" \ "5: \n" \
" movi %[err], %[efault] \n" \ " movi %[tmp], 2b \n" \
" jx %[tmp] \n" \ " movi %[err], %[efault] \n" \
" .previous \n" \ " jx %[tmp] \n" \
" .section __ex_table,\"a\" \n" \ " .previous \n" \
" .long 1b, 5b \n" \ " .section __ex_table,\"a\" \n" \
" .previous" \ " .long 1b, 5b \n" \
:[err] "+r"(err_), [tmp] "=r"(cb), [x] "=r"(x_)\ " .previous" \
:[addr] "r"(addr_), [efault] "i"(-EFAULT)) :[err] "+r"(err_), [tmp] "=r"(cb), [x] "+r"(__x) \
:[addr] "r"(addr_), [efault] "i"(-EFAULT)); \
(x_) = (__force __typeof__(*(addr_)))__x; \
} while (0)
/* /*