From: Arnd Bergmann

Sent: 16 February 2022 13:13

These two architectures implement 8-byte get_user() through
a memcpy() into a four-byte variable, which won't fit.

Use a temporary 64-bit variable instead here, and use a double
cast the way that risc-v and openrisc do to avoid compile-time
warnings.

...

 	case 4:								\
-		__get_user_asm("lw", (ptr), __gu_val, __gu_err);	\
+		__get_user_asm("lw", (ptr), x, __gu_err);		\
 		break;							\
-	case 8:								\
-		__gu_err = __copy_from_user(&__gu_val, ptr, 8);		\
-		if (__gu_err)						\
-			__gu_err = -EFAULT;				\
+	case 8: {							\
+		__u64 __x = 0;						\
+		__gu_err = raw_copy_from_user(&__x, ptr, 8) ?		\
+							-EFAULT : 0;	\
+		(x) = (typeof(x))(typeof((x) - (x)))__x;		\
 		break;							\

Wouldn't it be better to just fetch two 32bit values:
Something like (for LE - nios2 is definitely LE:
		__u32 val_lo, val_hi;
		__get_user_asm("lw", (ptr), val_lo, __gu_err);
		__get_user_asm("lw", (ptr) + 4, val_hi, __gu_err);
		x = val_lo | val_hi << 32;
		break;

	David

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