[PATCH 4/4] riscv: uaccess: use 'asm goto output' for get_user

Jisheng Zhang
2024-06-25T04:19:10Z

'asm goto output' generates noticeably better code since we don't need
to test the error etc, the exception just jumps to the error handling
directly.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
arch/riscv/include/asm/uaccess.h | 88 +++++++++++++++++++++++---------
1 file changed, 63 insertions(+), 25 deletions(-)

diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
index d8c44705b61d..d9c32b4f7d13 100644
--- a/arch/riscv/include/asm/uaccess.h
+++ b/arch/riscv/include/asm/uaccess.h
@@ -63,27 +63,54 @@
* call.
*/

-#define __get_user_asm(insn, x, ptr, err) \
+#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
+#define __get_user_asm(insn, x, ptr, label) \
+ asm_goto_output( \
+ "1:\n" \
+ " " insn " %0, %1\n" \
+ _ASM_EXTABLE_UACCESS_ERR(1b, %l2, %0) \
+ : "=&r" (x) \
+ : "m" (*(ptr)) : : label)
+#else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
+#define __get_user_asm(insn, x, ptr, label) \
do { \
- __typeof__(x) __x; \
+ long __gua_err = 0; \
__asm__ __volatile__ ( \
"1:\n" \
" " insn " %1, %2\n" \
"2:\n" \
_ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 2b, %0, %1) \
- : "+r" (err), "=&r" (__x) \
+ : "+r" (__gua_err), "=&r" (x) \
: "m" (*(ptr))); \
- (x) = __x; \
+ if (__gua_err) \
+ goto label; \
} while (0)
+#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */

#ifdef CONFIG_64BIT
-#define __get_user_8(x, ptr, err) \
- __get_user_asm("ld", x, ptr, err)
+#define __get_user_8(x, ptr, label) \
+ __get_user_asm("ld", x, ptr, label)
#else /* !CONFIG_64BIT */
-#define __get_user_8(x, ptr, err) \
+
+#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
+#define __get_user_8(x, ptr, label) \
+ asm_goto_output( \
+ "1:\n" \
+ " lw %0, %2\n" \
+ "2:\n" \
+ " lw %1, %3\n" \
+ _ASM_EXTABLE_UACCESS_ERR(1b, %l4, %0) \
+ _ASM_EXTABLE_UACCESS_ERR(2b, %l4, %0) \
+ : "=&r" (__lo), "=r" (__hi) \
+ : "m" (__ptr[__LSW]), "m" (__ptr[__MSW]) \
+ : : label)
+
+#else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
+#define __get_user_8(x, ptr, label) \
do { \
u32 __user *__ptr = (u32 __user *)(ptr); \
u32 __lo, __hi; \
+ long __gu8_err = 0; \
__asm__ __volatile__ ( \
"1:\n" \
" lw %1, %3\n" \
@@ -92,35 +119,51 @@ do { \
"3:\n" \
_ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 3b, %0, %1) \
_ASM_EXTABLE_UACCESS_ERR_ZERO(2b, 3b, %0, %1) \
- : "+r" (err), "=&r" (__lo), "=r" (__hi) \
+ : "+r" (__gu8_err), "=&r" (__lo), "=r" (__hi) \
: "m" (__ptr[__LSW]), "m" (__ptr[__MSW])); \
- if (err) \
+ if (__gu8_err) { \
__hi = 0; \
+ goto label; \
+ } \
(x) = (__typeof__(x))((__typeof__((x)-(x)))( \
(((u64)__hi << 32) | __lo))); \
} while (0)
+#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
+
#endif /* CONFIG_64BIT */

-#define __get_user_nocheck(x, __gu_ptr, __gu_err) \
+#define __get_user_nocheck(x, __gu_ptr, label) \
do { \
switch (sizeof(*__gu_ptr)) { \
case 1: \
- __get_user_asm("lb", (x), __gu_ptr, __gu_err); \
+ __get_user_asm("lb", (x), __gu_ptr, label); \
break; \
case 2: \
- __get_user_asm("lh", (x), __gu_ptr, __gu_err); \
+ __get_user_asm("lh", (x), __gu_ptr, label); \
break; \
case 4: \
- __get_user_asm("lw", (x), __gu_ptr, __gu_err); \
+ __get_user_asm("lw", (x), __gu_ptr, label); \
break; \
case 8: \
- __get_user_8((x), __gu_ptr, __gu_err); \
+ __get_user_8((x), __gu_ptr, label); \
break; \
default: \
BUILD_BUG(); \
} \
} while (0)

+#define __get_user_error(x, ptr, err) \
+do { \
+ __label__ __gu_failed; \
+ \
+ __get_user_nocheck(x, ptr, __gu_failed); \
+ err = 0; \
+ break; \
+__gu_failed: \
+ x = 0; \
+ err = -EFAULT; \
+} while (0)
+
/**
* __get_user: - Get a simple variable from user space, with less checking.
* @x: Variable to store result.
@@ -145,13 +188,16 @@ do { \
({ \
const __typeof__(*(ptr)) __user *__gu_ptr = (ptr); \
long __gu_err = 0; \
+ __typeof__(x) __gu_val; \
\
__chk_user_ptr(__gu_ptr); \
\
__enable_user_access(); \
- __get_user_nocheck(x, __gu_ptr, __gu_err); \
+ __get_user_error(__gu_val, __gu_ptr, __gu_err); \
__disable_user_access(); \
\
+ (x) = __gu_val; \
+ \
__gu_err; \
})

@@ -336,13 +382,7 @@ unsigned long __must_check clear_user(void __user *to, unsigned long n)
}

#define __get_kernel_nofault(dst, src, type, err_label) \
-do { \
- long __kr_err = 0; \
- \
- __get_user_nocheck(*((type *)(dst)), (type *)(src), __kr_err); \
- if (unlikely(__kr_err)) \
- goto err_label; \
-} while (0)
+ __get_user_nocheck(*((type *)(dst)), (type *)(src), err_label);

#define __put_kernel_nofault(dst, src, type, err_label) \
__put_user_nocheck(*((type *)(src)), (type *)(dst), err_label);
@@ -364,11 +404,9 @@ static inline void user_access_restore(unsigned long enabled) { }
__put_user_nocheck(x, (ptr), label);

#define unsafe_get_user(x, ptr, label) do { \
- long __kr_err = 0; \
__inttype(*(ptr)) __gu_val; \
- __get_user_nocheck(__gu_val, (ptr), __kr_err); \
+ __get_user_nocheck(__gu_val, (ptr), label); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
- if (__kr_err) goto label; \
} while (0)

/*
--
2.43.0