metag: checksum.h: fix carry in csum_tcpudp_nofold

In csum_tcpudp_nofold, add 1 if the carry bit is set after adding the
destination IP address (32 bits) to the checksum (16 bits).

The lack of carry handling for this particular addition meant that a
destination address of *.*.255.255 (e.g. certain broadcasts) sometimes
resulted in an incorrect checksum. This bug has been present in the Meta
port since the code was written in the 2.4 days.

Reported-by: Marcin Nowakowski <Marcin.Nowakowski@pure.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/metag/include/asm/checksum.h b/arch/metag/include/asm/checksum.h
index 999bf761a732..08dd1cc65799 100644
--- a/arch/metag/include/asm/checksum.h
+++ b/arch/metag/include/asm/checksum.h
@@ -64,7 +64,8 @@ static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
                                         __wsum sum)
 {
         unsigned long len_proto = (proto + len) << 8;
-        asm ("ADD    %0, %0, %1\n"
+        asm ("ADDS   %0, %0, %1\n"
+             "ADDCS  %0, %0, #1\n"
              "ADDS   %0, %0, %2\n"
              "ADDCS  %0, %0, #1\n"
              "ADDS   %0, %0, %3\n"