m68k: Provide __{get,put}_kernel_nofault

Allow non-faulting access to kernel addresses without overriding the
address space.  Implemented by passing the instruction name to the
low-level assembly macros as an argument, and force the use of the
normal move instructions for kernel access.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Link: https://lore.kernel.org/r/20210916070405.52750-6-hch@lst.deSigned-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/include/asm/uaccess.h

@@ -39,9 +39,9 @@ static inline int access_ok(const void __user *addr,
 #define	MOVES	"move"
 #endif
 
-#define __put_user_asm(res, x, ptr, bwl, reg, err)	\
+#define __put_user_asm(inst, res, x, ptr, bwl, reg, err) \
 asm volatile ("\n"					\
-	"1:	"MOVES"."#bwl"	%2,%1\n"		\
+	"1:	"inst"."#bwl"	%2,%1\n"		\
 	"2:\n"						\
 	"	.section .fixup,\"ax\"\n"		\
 	"	.even\n"				\
@@ -57,13 +57,13 @@ asm volatile ("\n"					\
 	: "+d" (res), "=m" (*(ptr))			\
 	: #reg (x), "i" (err))
 
-#define __put_user_asm8(res, x, ptr)				\
+#define __put_user_asm8(inst, res, x, ptr)			\
 do {								\
 	const void *__pu_ptr = (const void __force *)(ptr);	\
 								\
 	asm volatile ("\n"					\
-		"1:	"MOVES".l %2,(%1)+\n"			\
-		"2:	"MOVES".l %R2,(%1)\n"			\
+		"1:	"inst".l %2,(%1)+\n"			\
+		"2:	"inst".l %R2,(%1)\n"			\
 		"3:\n"						\
 		"	.section .fixup,\"ax\"\n"		\
 		"	.even\n"				\
@@ -94,16 +94,16 @@ do {								\
 	__chk_user_ptr(ptr);						\
 	switch (sizeof (*(ptr))) {					\
 	case 1:								\
-		__put_user_asm(__pu_err, __pu_val, ptr, b, d, -EFAULT);	\
+		__put_user_asm(MOVES, __pu_err, __pu_val, ptr, b, d, -EFAULT); \
 		break;							\
 	case 2:								\
-		__put_user_asm(__pu_err, __pu_val, ptr, w, r, -EFAULT);	\
+		__put_user_asm(MOVES, __pu_err, __pu_val, ptr, w, r, -EFAULT); \
 		break;							\
 	case 4:								\
-		__put_user_asm(__pu_err, __pu_val, ptr, l, r, -EFAULT);	\
+		__put_user_asm(MOVES, __pu_err, __pu_val, ptr, l, r, -EFAULT); \
 		break;							\
 	case 8:								\
-		__put_user_asm8(__pu_err, __pu_val, ptr);		\
+		__put_user_asm8(MOVES, __pu_err, __pu_val, ptr);	\
 		break;							\
 	default:							\
 		BUILD_BUG();						\
@@ -113,10 +113,10 @@ do {								\
 #define put_user(x, ptr)	__put_user(x, ptr)
 
 
-#define __get_user_asm(res, x, ptr, type, bwl, reg, err) ({		\
+#define __get_user_asm(inst, res, x, ptr, type, bwl, reg, err) ({	\
 	type __gu_val;							\
 	asm volatile ("\n"						\
-		"1:	"MOVES"."#bwl"	%2,%1\n"			\
+		"1:	"inst"."#bwl"	%2,%1\n"			\
 		"2:\n"							\
 		"	.section .fixup,\"ax\"\n"			\
 		"	.even\n"					\
@@ -134,7 +134,7 @@ do {								\
 	(x) = (__force typeof(*(ptr)))(__force unsigned long)__gu_val;	\
 })
 
-#define __get_user_asm8(res, x, ptr)					\
+#define __get_user_asm8(inst, res, x, ptr) 				\
 do {									\
 	const void *__gu_ptr = (const void __force *)(ptr);		\
 	union {								\
@@ -143,8 +143,8 @@ do {									\
 	} __gu_val;							\
 									\
 	asm volatile ("\n"						\
-		"1:	"MOVES".l	(%2)+,%1\n"			\
-		"2:	"MOVES".l	(%2),%R1\n"			\
+		"1:	"inst".l (%2)+,%1\n"				\
+		"2:	"inst".l (%2),%R1\n"				\
 		"3:\n"							\
 		"	.section .fixup,\"ax\"\n"			\
 		"	.even\n"					\
@@ -172,16 +172,16 @@ do {									\
 	__chk_user_ptr(ptr);						\
 	switch (sizeof(*(ptr))) {					\
 	case 1:								\
-		__get_user_asm(__gu_err, x, ptr, u8, b, d, -EFAULT);	\
+		__get_user_asm(MOVES, __gu_err, x, ptr, u8, b, d, -EFAULT); \
 		break;							\
 	case 2:								\
-		__get_user_asm(__gu_err, x, ptr, u16, w, r, -EFAULT);	\
+		__get_user_asm(MOVES, __gu_err, x, ptr, u16, w, r, -EFAULT); \
 		break;							\
 	case 4:								\
-		__get_user_asm(__gu_err, x, ptr, u32, l, r, -EFAULT);	\
+		__get_user_asm(MOVES, __gu_err, x, ptr, u32, l, r, -EFAULT); \
 		break;							\
 	case 8:								\
-		__get_user_asm8(__gu_err, x, ptr);			\
+		__get_user_asm8(MOVES, __gu_err, x, ptr);		\
 		break;							\
 	default:							\
 		BUILD_BUG();						\
@@ -330,16 +330,19 @@ __constant_copy_to_user(void __user *to, const void *from, unsigned long n)
 
 	switch (n) {
 	case 1:
-		__put_user_asm(res, *(u8 *)from, (u8 __user *)to, b, d, 1);
+		__put_user_asm(MOVES, res, *(u8 *)from, (u8 __user *)to,
+				b, d, 1);
 		break;
 	case 2:
-		__put_user_asm(res, *(u16 *)from, (u16 __user *)to, w, r, 2);
+		__put_user_asm(MOVES, res, *(u16 *)from, (u16 __user *)to,
+				w, r, 2);
 		break;
 	case 3:
 		__constant_copy_to_user_asm(res, to, from, tmp, 3, w, b,);
 		break;
 	case 4:
-		__put_user_asm(res, *(u32 *)from, (u32 __user *)to, l, r, 4);
+		__put_user_asm(MOVES, res, *(u32 *)from, (u32 __user *)to,
+				l, r, 4);
 		break;
 	case 5:
 		__constant_copy_to_user_asm(res, to, from, tmp, 5, l, b,);
@@ -388,6 +391,66 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 #define INLINE_COPY_FROM_USER
 #define INLINE_COPY_TO_USER
 
+#define HAVE_GET_KERNEL_NOFAULT
+
+#define __get_kernel_nofault(dst, src, type, err_label)			\
+do {									\
+	type *__gk_dst = (type *)(dst);					\
+	type *__gk_src = (type *)(src);					\
+	int __gk_err = 0;						\
+									\
+	switch (sizeof(type)) {						\
+	case 1:								\
+		__get_user_asm("move", __gk_err, *__gk_dst, __gk_src,	\
+				u8, b, d, -EFAULT);			\
+		break;							\
+	case 2:								\
+		__get_user_asm("move", __gk_err, *__gk_dst, __gk_src,	\
+				u16, w, r, -EFAULT);			\
+		break;							\
+	case 4:								\
+		__get_user_asm("move", __gk_err, *__gk_dst, __gk_src,	\
+				u32, l, r, -EFAULT);			\
+		break;							\
+	case 8:								\
+		__get_user_asm8("move", __gk_err, *__gk_dst, __gk_src);	\
+		break;							\
+	default:							\
+		BUILD_BUG();						\
+	}								\
+	if (unlikely(__gk_err))						\
+		goto err_label;						\
+} while (0)
+
+#define __put_kernel_nofault(dst, src, type, err_label)			\
+do {									\
+	type __pk_src = *(type *)(src);					\
+	type *__pk_dst = (type *)(dst);					\
+	int __pk_err = 0;						\
+									\
+	switch (sizeof(type)) {						\
+	case 1:								\
+		__put_user_asm("move", __pk_err, __pk_src, __pk_dst,	\
+				b, d, -EFAULT);				\
+		break;							\
+	case 2:								\
+		__put_user_asm("move", __pk_err, __pk_src, __pk_dst,	\
+				w, r, -EFAULT);				\
+		break;							\
+	case 4:								\
+		__put_user_asm("move", __pk_err, __pk_src, __pk_dst,	\
+				l, r, -EFAULT);				\
+		break;							\
+	case 8:								\
+		__put_user_asm8("move", __pk_err, __pk_src, __pk_dst);	\
+		break;							\
+	default:							\
+		BUILD_BUG();						\
+	}								\
+	if (unlikely(__pk_err))						\
+		goto err_label;						\
+} while (0)
+
 #define user_addr_max() \
 	(uaccess_kernel() ? ~0UL : TASK_SIZE)