arm: switch to csum_and_copy_from_user()

Note that csum_partial_copy_from_user() is in assembler here,
so I'm leaving it alone and just providing the wrapper for
it.  When/if we go for switching arm to user_access_{begin,end}()
(doing domain switches in those), somebody well need to look
into that one.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/arm/include/asm/checksum.h

@@ -40,6 +40,20 @@ csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum);
 __wsum
 csum_partial_copy_from_user(const void __user *src, void *dst, int len, __wsum sum, int *err_ptr);
 
+#define _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
+static inline
+__wsum csum_and_copy_from_user (const void __user *src, void *dst,
+				      int len, __wsum sum, int *err_ptr)
+{
+	if (access_ok(src, len))
+		return csum_partial_copy_from_user(src, dst, len, sum, err_ptr);
+
+	if (len)
+		*err_ptr = -EFAULT;
+
+	return sum;
+}
+
 /*
  * 	Fold a partial checksum without adding pseudo headers
  */