The type of sum in csum_tcpudp_nofold is "unsigned int", so when we assign
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>
diff --git a/include/asm-mips/checksum.h b/include/asm-mips/checksum.h
index 2ff53db..b09f897 100644
--- a/include/asm-mips/checksum.h
+++ b/include/asm-mips/checksum.h
@@ -150,7 +150,7 @@
" 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)