Re: [PATCH v6 0/2] lib: checksum: Fix issues with checksum tests

From: Guenter Roeck
Date: Sun Feb 11 2024 - 14:18:48 EST


On 2/7/24 16:22, Charlie Jenkins wrote:
The ip_fast_csum and csum_ipv6_magic tests did not have the data
types properly casted, and improperly misaligned data.

Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>

I sorted out most of the problems with this version, but I still get:

# test_csum_ipv6_magic: ASSERTION FAILED at lib/checksum_kunit.c:513
Expected ( u64)csum_result == ( u64)expected, but
( u64)csum_result == 16630 (0x40f6)
( u64)expected == 65535 (0xffff)
not ok 5 test_csum_ipv6_magic

on m68k:q800. This is suspicious because there is no 0xffff in
expected_csum_ipv6_magic[]. With some debugging information:

####### num_tests=86 i=84 expect array size=84
####### MAX_LEN=512 WORD_ALIGNMENT=4 magic data size=42

That means the loop

for (int i = 0; i < num_tests; i++) {
expected = (__force __sum16)expected_csum_ipv6_magic[i];

will access data beyond the end of the expected_csum_ipv6_magic[] array,
possibly because m68k doesn't pad struct csum_ipv6_magic_data to 44 bytes.

In this context, is the comment about proto having to be 0 really true ?
It seems to me that the calculated checksum must be identical on both
little and big endian systems. After all, they need to be able to talk
to each other.