[PATCH 2/4] riscv: uaccess: use input constraints for ptr of __put_user

Jisheng Zhang
2024-06-25T04:19:07Z

I believe the output constraints "=m" is not necessary, because
the instruction itself is "write", we don't need the compiler
to "write" for us. So tell compiler we read from memory instead
of writing.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
arch/riscv/include/asm/uaccess.h | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
index 09d4ca37522c..84b084e388a7 100644
--- a/arch/riscv/include/asm/uaccess.h
+++ b/arch/riscv/include/asm/uaccess.h
@@ -186,11 +186,11 @@ do { \
__typeof__(*(ptr)) __x = x; \
__asm__ __volatile__ ( \
"1:\n" \
- " " insn " %z2, %1\n" \
+ " " insn " %z1, %2\n" \
"2:\n" \
_ASM_EXTABLE_UACCESS_ERR(1b, 2b, %0) \
- : "+r" (err), "=m" (*(ptr)) \
- : "rJ" (__x)); \
+ : "+r" (err) \
+ : "rJ" (__x), "m"(*(ptr))); \
} while (0)

#ifdef CONFIG_64BIT
@@ -203,16 +203,16 @@ do { \
u64 __x = (__typeof__((x)-(x)))(x); \
__asm__ __volatile__ ( \
"1:\n" \
- " sw %z3, %1\n" \
+ " sw %z1, %3\n" \
"2:\n" \
- " sw %z4, %2\n" \
+ " sw %z2, %4\n" \
"3:\n" \
_ASM_EXTABLE_UACCESS_ERR(1b, 3b, %0) \
_ASM_EXTABLE_UACCESS_ERR(2b, 3b, %0) \
- : "+r" (err), \
- "=m" (__ptr[__LSW]), \
- "=m" (__ptr[__MSW]) \
- : "rJ" (__x), "rJ" (__x >> 32)); \
+ : "+r" (err) \
+ : "rJ" (__x), "rJ" (__x >> 32), \
+ "m" (__ptr[__LSW]), \
+ "m" (__ptr[__MSW])); \
} while (0)
#endif /* CONFIG_64BIT */

--
2.43.0