sw64: fix floating point register corruption

Sunway inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5GFS3

--------------------------------

When csum_partial_copy_from_user is called in an interrupt,
__copy_from_user will modify floating point register f10-f15
without restore register value. This will cause the value of
the userspace register to be corrupted. Use memcpy() instead
when called from kernel space.
Signed-off-by: NZhou Xuemei <zhouxuemei@wxiat.com>
Signed-off-by: NGu Zitao <guzitao@wxiat.com>

arch/sw_64/lib/csum_partial_copy.c

@@ -61,7 +61,11 @@ csum_partial_cfu_dest_aligned(const unsigned long __user *src,
 	unsigned long checksum = ~0U;
 	int err = 0;
 
-	err = __copy_from_user(dst, src, len+8);
+	if (likely(!uaccess_kernel()))
+		err = __copy_from_user(dst, src, len + 8);
+	else
+		memcpy(dst, src, len + 8);
+
 	while (len > 0) {
 		word = *dst;
 		checksum += word;
@@ -89,7 +93,10 @@ csum_partial_cfu_dest_unaligned(const unsigned long __user *src,
 	unsigned long checksum = ~0U;
 	int err = 0;
 
-	err = __copy_from_user(dst, src, len+8);
+	if (likely(!uaccess_kernel()))
+		err = __copy_from_user(dst, src, len + 8);
+	else
+		memcpy(dst, src, len + 8);
 
 	dst = (unsigned long *)((unsigned long)dst & (~7UL));
 	word = *dst;