Re: [tip:x86/core 1/1] arch/x86/um/../lib/csum-partial_64.c:98:12: error: implicit declaration of function 'load_unaligned_zeropad'

Eric Dumazet
2021-11-25T04:10:59Z

On Wed, Nov 24, 2021 at 8:00 PM Eric Dumazet <edumazet@google.com> wrote:

>
> It is an issue in general, not in standard cases because network
> headers are aligned.
>
> I think it came when I folded csum_partial() and do_csum(), I forgot
> to ror() the seed.
>
> I suspect the following would help:
>
> diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c
> index 1eb8f2d11f7c785be624eba315fe9ca7989fd56d..ee7b0e7a6055bcbef42d22f7e1d8f52ddbd6be6d
> 100644
> --- a/arch/x86/lib/csum-partial_64.c
> +++ b/arch/x86/lib/csum-partial_64.c
> @@ -41,6 +41,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
> if (unlikely(odd)) {
> if (unlikely(len == 0))
> return sum;
> + temp64 = ror32((__force u64)sum, 8);
> temp64 += (*(unsigned char *)buff << 8);
> len--;
> buff++;
>
>

It is a bit late here, I will test the following later this week.

We probably can remove one conditional jump at the end of the function

diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c
index 1eb8f2d11f7c785be624eba315fe9ca7989fd56d..15986ad42ed5ccb8241ff467a34188cf901ec98e
100644
--- a/arch/x86/lib/csum-partial_64.c
+++ b/arch/x86/lib/csum-partial_64.c
@@ -41,9 +41,11 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
if (unlikely(odd)) {
if (unlikely(len == 0))
return sum;
+ temp64 = ror32((__force u64)sum, 8);
temp64 += (*(unsigned char *)buff << 8);
len--;
buff++;
+ odd = 8;
}

while (unlikely(len >= 64)) {
@@ -129,10 +131,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
#endif
}
result = add32_with_carry(temp64 >> 32, temp64 & 0xffffffff);
- if (unlikely(odd)) {
- result = from32to16(result);
- result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
- }
+ ror32(result, odd);
return (__force __wsum)result;
}
EXPORT_SYMBOL(csum_partial);