The type of sum in csum_tcpudp_nofold is "unsigned int", so when we a…

…ssign

to it in an asm() block, and we're running on a system with 64-bit
registers, it is vitally important that we sign extend it correctly before
returning to C.  Otherwise the stray high bits will be preserved into
csum_fold, and on the SB-1 processor, 32-bit arithmetic on a non
sign-extended register will yield surprising results.
    
This caused incorrect checksums in some UDP packets for NFS root.  The
problem was mild when using a 10.0.1.x IP address, but severe when
using 192.168.1.x.
    
Signed-off-by: Daniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-mips/checksum.h

@@ -150,7 +150,7 @@ static inline unsigned int csum_tcpudp_nofold(unsigned long saddr,
 	"	daddu	%0, %4		\n"
 	"	dsll32	$1, %0, 0	\n"
 	"	daddu	%0, $1		\n"
-	"	dsrl32	%0, %0, 0	\n"
+	"	dsra32	%0, %0, 0	\n"
 #endif
 	"	.set	pop"
 	: "=r" (sum)