x86/uaccess: utilize CONFIG_CC_HAS_ASM_GOTO_OUTPUT
Clang-11 shipped support for outputs to asm goto statments along the
fallthrough path. Double up some of the get_user() and related macros
to be able to take advantage of this extended GNU C extension. This
should help improve the generated code's performance for these accesses.
Cc: Bill Wendling <morbo@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 4c2f8bb..aa60c23 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -310,6 +310,55 @@
} \
} while (0)
+#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
+
+#ifdef CONFIG_X86_32
+#define __get_user_asm_u64(x, ptr, label) do { \
+ unsigned int __gu_low, __gu_high; \
+ const unsigned int __user *__gu_ptr; \
+ __gu_ptr = (const void __user *)(ptr); \
+ __get_user_asm(__gu_low, ptr, "l", "=r", label); \
+ __get_user_asm(__gu_high, ptr+1, "l", "=r", label); \
+ (x) = ((unsigned long long)__gu_high << 32) | __gu_low; \
+} while (0)
+#else
+#define __get_user_asm_u64(x, ptr, label) \
+ __get_user_asm(x, ptr, "q", "=r", label)
+#endif
+
+#define __get_user_size(x, ptr, size, label) \
+do { \
+ __chk_user_ptr(ptr); \
+ switch (size) { \
+ unsigned char x_u8__; \
+ case 1: \
+ __get_user_asm(x_u8__, ptr, "b", "=q", label); \
+ (x) = x_u8__; \
+ break; \
+ case 2: \
+ __get_user_asm(x, ptr, "w", "=r", label); \
+ break; \
+ case 4: \
+ __get_user_asm(x, ptr, "l", "=r", label); \
+ break; \
+ case 8: \
+ __get_user_asm_u64(x, ptr, label); \
+ break; \
+ default: \
+ (x) = __get_user_bad(); \
+ } \
+} while (0)
+
+#define __get_user_asm(x, addr, itype, ltype, label) \
+ asm_volatile_goto("\n" \
+ "1: mov"itype" %[umem],%[output]\n" \
+ _ASM_EXTABLE_UA(1b, %l2) \
+ : [output] ltype(x) \
+ : [umem] "m" (__m(addr)) \
+ : : label)
+
+#else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT
+
#ifdef CONFIG_X86_32
#define __get_user_asm_u64(x, ptr, retval) \
({ \
@@ -378,6 +427,8 @@
: [umem] "m" (__m(addr)), \
[efault] "i" (-EFAULT), "0" (err))
+#endif // CONFIG_CC_ASM_GOTO_OUTPUT
+
/* FIXME: this hack is definitely wrong -AK */
struct __large_struct { unsigned long buf[100]; };
#define __m(x) (*(struct __large_struct __user *)(x))
@@ -452,6 +503,14 @@
#define unsafe_put_user(x, ptr, label) \
__put_user_size((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), label)
+#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
+#define unsafe_get_user(x, ptr, err_label) \
+do { \
+ __inttype(*(ptr)) __gu_val; \
+ __get_user_size(__gu_val, (ptr), sizeof(*(ptr)), err_label); \
+ (x) = (__force __typeof__(*(ptr)))__gu_val; \
+} while (0)
+#else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT
#define unsafe_get_user(x, ptr, err_label) \
do { \
int __gu_err; \
@@ -460,6 +519,7 @@
(x) = (__force __typeof__(*(ptr)))__gu_val; \
if (unlikely(__gu_err)) goto err_label; \
} while (0)
+#endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT
/*
* We want the unsafe accessors to always be inlined and use
@@ -486,6 +546,11 @@
#define HAVE_GET_KERNEL_NOFAULT
+#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
+#define __get_kernel_nofault(dst, src, type, err_label) \
+ __get_user_size(*((type *)(dst)), (__force type __user *)(src), \
+ sizeof(type), err_label)
+#else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT
#define __get_kernel_nofault(dst, src, type, err_label) \
do { \
int __kr_err; \
@@ -495,6 +560,7 @@
if (unlikely(__kr_err)) \
goto err_label; \
} while (0)
+#endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT
#define __put_kernel_nofault(dst, src, type, err_label) \
__put_user_size(*((type *)(src)), (__force type __user *)(dst), \
