MIPS: Add 'memory' clobber to csum_ipv6_magic() inline assembler

[ Upstream commit d55347bfe4e66dce2e1e7501e5492f4af3e315f8 ]

After 'lib: checksum: Use aligned accesses for ip_fast_csum and
csum_ipv6_magic tests' was applied, the test_csum_ipv6_magic unit test
started failing for all mips platforms, both little and bit endian.
Oddly enough, adding debug code into test_csum_ipv6_magic() made the
problem disappear.

The gcc manual says:

"The "memory" clobber tells the compiler that the assembly code performs
 memory reads or writes to items other than those listed in the input
 and output operands (for example, accessing the memory pointed to by one
 of the input parameters)
"

This is definitely the case for csum_ipv6_magic(). Indeed, adding the
'memory' clobber fixes the problem.

Cc: Charlie Jenkins <charlie@rivosinc.com>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/mips/include/asm/checksum.h b/arch/mips/include/asm/checksum.h
index 5f80c28f525346b77284740fe7e61a4aec7ae225..6c837a256cf66c3b76291986d0ef60a982a90623 100644 (file)
--- a/arch/mips/include/asm/checksum.h
+++ b/arch/mips/include/asm/checksum.h
@@ -242,7 +242,8 @@ static __inline__ __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
        "       .set    pop"
        : "=&r" (sum), "=&r" (tmp)
        : "r" (saddr), "r" (daddr),
-         "0" (htonl(len)), "r" (htonl(proto)), "r" (sum));
+         "0" (htonl(len)), "r" (htonl(proto)), "r" (sum)
+       : "memory");
 
        return csum_fold(sum);
 }