sparc: Add full proper error handling to strncpy_from_user().

Linus removed the end-of-address-space hackery from
fs/namei.c:do_getname() so we really have to validate these edge
conditions and cannot cheat any more (as x86 used to as well).

Move to a common C implementation like x86 did.  And if both
src and dst are sufficiently aligned we'll do word at a time
copies and checks as well.

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/include/asm/uaccess.h

@@ -5,4 +5,7 @@
 #else
 #include <asm/uaccess_32.h>
 #endif
+
+extern long strncpy_from_user(char *dest, const char __user *src, long count);
+
 #endif