Re: [PATCH v3] arch/microblaze: add support for get_user() of size 8 bytes

[Linus Torvalds <torvalds@linux-foundation.org>]

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On Sun, Sep 1, 2019 at 7:10 PM Randy Dunlap <rdunlap@infradead.org> wrote:
>
> I guess we need a way to coerce that to call get_user_1(),
> such as a typecast.  This _seems_ to work (i.e., call get_user_1()):

No, I oversimplified.

Try this slightly modified patch instead.

                 Linus

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 arch/microblaze/include/asm/uaccess.h | 42 ++++++++---------------------------
 1 file changed, 9 insertions(+), 33 deletions(-)

diff --git a/arch/microblaze/include/asm/uaccess.h b/arch/microblaze/include/asm/uaccess.h
index bff2a71c828a..a1f206b90753 100644
--- a/arch/microblaze/include/asm/uaccess.h
+++ b/arch/microblaze/include/asm/uaccess.h
@@ -163,44 +163,15 @@ extern long __user_bad(void);
  * Returns zero on success, or -EFAULT on error.
  * On error, the variable @x is set to zero.
  */
-#define get_user(x, ptr)						\
-	__get_user_check((x), (ptr), sizeof(*(ptr)))
-
-#define __get_user_check(x, ptr, size)					\
-({									\
-	unsigned long __gu_val = 0;					\
-	const typeof(*(ptr)) __user *__gu_addr = (ptr);			\
-	int __gu_err = 0;						\
-									\
-	if (access_ok(__gu_addr, size)) {			\
-		switch (size) {						\
-		case 1:							\
-			__get_user_asm("lbu", __gu_addr, __gu_val,	\
-				       __gu_err);			\
-			break;						\
-		case 2:							\
-			__get_user_asm("lhu", __gu_addr, __gu_val,	\
-				       __gu_err);			\
-			break;						\
-		case 4:							\
-			__get_user_asm("lw", __gu_addr, __gu_val,	\
-				       __gu_err);			\
-			break;						\
-		default:						\
-			__gu_err = __user_bad();			\
-			break;						\
-		}							\
-	} else {							\
-		__gu_err = -EFAULT;					\
-	}								\
-	x = (__force typeof(*(ptr)))__gu_val;				\
-	__gu_err;							\
+#define get_user(x, ptr) ({				\
+	const typeof(*(ptr)) __user *__gu_ptr = (ptr);	\
+	access_ok(__gu_ptr, sizeof(*__gu_ptr)) ?	\
+		__get_user(x, __gu_ptr) : -EFAULT;	\
 })
 
 #define __get_user(x, ptr)						\
 ({									\
 	unsigned long __gu_val = 0;					\
-	/*unsigned long __gu_ptr = (unsigned long)(ptr);*/		\
 	long __gu_err;							\
 	switch (sizeof(*(ptr))) {					\
 	case 1:								\
@@ -212,6 +183,11 @@ extern long __user_bad(void);
 	case 4:								\
 		__get_user_asm("lw", (ptr), __gu_val, __gu_err);	\
 		break;							\
+	case 8:								\
+		__gu_err = __copy_from_user(&__gu_val, ptr, 8);		\
+		if (__gu_err)						\
+			__gu_err = -EFAULT;				\
+		break;							\
 	default:							\
 		/* __gu_val = 0; __gu_err = -EINVAL;*/ __gu_err = __user_bad();\
 	}								\