On Sun, Feb 11, 2024 at 08:08:37AM -0800, Guenter Roeck wrote:
> 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@xxxxxxxxxxxx>
> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
> arch/mips/include/asm/checksum.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/mips/include/asm/checksum.h b/arch/mips/include/asm/checksum.h
> index 4044eaf989ac..0921ddda11a4 100644
> --- a/arch/mips/include/asm/checksum.h
> +++ b/arch/mips/include/asm/checksum.h
> @@ -241,7 +241,8 @@ 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);
> }
> --
> 2.39.2
>
Thank you for looking into this. It fixed the failure on my mips64el
qemu setup.
Reviewed-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
