riscv: extable: add a dedicated uaccess handler

Inspired by commit 2e77a62cb3a6 ("arm64: extable: add a dedicated
uaccess handler"), do similar to riscv to add a dedicated uaccess
exception handler to update registers in exception context and
subsequently return back into the function which faulted, so we remove
the need for fixups specialized to each faulting instruction.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 22 insertions, 53 deletions

diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
index 40e6099af488..c701a5e57a2b 100644
--- a/arch/riscv/include/asm/uaccess.h
+++ b/arch/riscv/include/asm/uaccess.h
@@ -81,22 +81,14 @@ static inline int __access_ok(unsigned long addr, unsigned long size)
 
 #define __get_user_asm(insn, x, ptr, err)			\
 do {								\
-	uintptr_t __tmp;					\
 	__typeof__(x) __x;					\
 	__asm__ __volatile__ (					\
 		"1:\n"						\
-		"	" insn " %1, %3\n"			\
+		"	" insn " %1, %2\n"			\
 		"2:\n"						\
-		"	.section .fixup,\"ax\"\n"		\
-		"	.balign 4\n"				\
-		"3:\n"						\
-		"	li %0, %4\n"				\
-		"	li %1, 0\n"				\
-		"	jump 2b, %2\n"				\
-		"	.previous\n"				\
-			_ASM_EXTABLE(1b, 3b)			\
-		: "+r" (err), "=&r" (__x), "=r" (__tmp)		\
-		: "m" (*(ptr)), "i" (-EFAULT));			\
+		_ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 2b, %0, %1)	\
+		: "+r" (err), "=&r" (__x)			\
+		: "m" (*(ptr)));				\
 	(x) = __x;						\
 } while (0)
 
@@ -108,27 +100,18 @@ do {								\
 do {								\
 	u32 __user *__ptr = (u32 __user *)(ptr);		\
 	u32 __lo, __hi;						\
-	uintptr_t __tmp;					\
 	__asm__ __volatile__ (					\
 		"1:\n"						\
-		"	lw %1, %4\n"				\
+		"	lw %1, %3\n"				\
 		"2:\n"						\
-		"	lw %2, %5\n"				\
+		"	lw %2, %4\n"				\
 		"3:\n"						\
-		"	.section .fixup,\"ax\"\n"		\
-		"	.balign 4\n"				\
-		"4:\n"						\
-		"	li %0, %6\n"				\
-		"	li %1, 0\n"				\
-		"	li %2, 0\n"				\
-		"	jump 3b, %3\n"				\
-		"	.previous\n"				\
-			_ASM_EXTABLE(1b, 4b)			\
-			_ASM_EXTABLE(2b, 4b)			\
-		: "+r" (err), "=&r" (__lo), "=r" (__hi),	\
-			"=r" (__tmp)				\
-		: "m" (__ptr[__LSW]), "m" (__ptr[__MSW]),	\
-			"i" (-EFAULT));				\
+		_ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 3b, %0, %1)	\
+		_ASM_EXTABLE_UACCESS_ERR_ZERO(2b, 3b, %0, %1)	\
+		: "+r" (err), "=&r" (__lo), "=r" (__hi)		\
+		: "m" (__ptr[__LSW]), "m" (__ptr[__MSW]));	\
+	if (err)						\
+		__hi = 0;					\
 	(x) = (__typeof__(x))((__typeof__((x)-(x)))(		\
 		(((u64)__hi << 32) | __lo)));			\
 } while (0)
@@ -216,21 +199,14 @@ do {								\
 
 #define __put_user_asm(insn, x, ptr, err)			\
 do {								\
-	uintptr_t __tmp;					\
 	__typeof__(*(ptr)) __x = x;				\
 	__asm__ __volatile__ (					\
 		"1:\n"						\
-		"	" insn " %z3, %2\n"			\
+		"	" insn " %z2, %1\n"			\
 		"2:\n"						\
-		"	.section .fixup,\"ax\"\n"		\
-		"	.balign 4\n"				\
-		"3:\n"						\
-		"	li %0, %4\n"				\
-		"	jump 2b, %1\n"				\
-		"	.previous\n"				\
-			_ASM_EXTABLE(1b, 3b)			\
-		: "+r" (err), "=r" (__tmp), "=m" (*(ptr))	\
-		: "rJ" (__x), "i" (-EFAULT));			\
+		_ASM_EXTABLE_UACCESS_ERR(1b, 2b, %0)		\
+		: "+r" (err), "=m" (*(ptr))			\
+		: "rJ" (__x));					\
 } while (0)
 
 #ifdef CONFIG_64BIT
@@ -241,25 +217,18 @@ do {								\
 do {								\
 	u32 __user *__ptr = (u32 __user *)(ptr);		\
 	u64 __x = (__typeof__((x)-(x)))(x);			\
-	uintptr_t __tmp;					\
 	__asm__ __volatile__ (					\
 		"1:\n"						\
-		"	sw %z4, %2\n"				\
+		"	sw %z3, %1\n"				\
 		"2:\n"						\
-		"	sw %z5, %3\n"				\
+		"	sw %z4, %2\n"				\
 		"3:\n"						\
-		"	.section .fixup,\"ax\"\n"		\
-		"	.balign 4\n"				\
-		"4:\n"						\
-		"	li %0, %6\n"				\
-		"	jump 3b, %1\n"				\
-		"	.previous\n"				\
-			_ASM_EXTABLE(1b, 4b)			\
-			_ASM_EXTABLE(2b, 4b)			\
-		: "+r" (err), "=r" (__tmp),			\
+		_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), "i" (-EFAULT));	\
+		: "rJ" (__x), "rJ" (__x >> 32));		\
 } while (0)
 #endif /* CONFIG_64BIT */