Subject: Re: [PATCH bpf-next] selftests/bpf: Fix error reporting from sock_fields programs

From: Jakub Sitnicki <[email-masked]>
Date: Sun, 27 Feb 2022 17:16:24 +0100

On Fri, Feb 25, 2022 at 12:13 PM -08, Martin KaFai Lau wrote:
> On Fri, Feb 25, 2022 at 07:41:30PM +0100, Jakub Sitnicki wrote:
>> The helper macro that records an error in BPF programs that exercise sock
>> fields access has been indavertedly broken by adaptation work that happened
>> in commit b18c1f0aa477 ("bpf: selftest: Adapt sock_fields test to use skel
>> and global variables").
>> 
>> BPF_NOEXIST flag cannot be used to update BPF_MAP_TYPE_ARRAY. The operation
>> always fails with -EEXIST, which in turn means the error never gets
>> recorded, and the checks for errors always pass.
>> 
>> Revert the change in update flags.
>> 
>> Fixes: b18c1f0aa477 ("bpf: selftest: Adapt sock_fields test to use skel and global variables")
>> Signed-off-by: Jakub Sitnicki <[email-masked]>
>> ---
>>  tools/testing/selftests/bpf/progs/test_sock_fields.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/tools/testing/selftests/bpf/progs/test_sock_fields.c b/tools/testing/selftests/bpf/progs/test_sock_fields.c
>> index 246f1f001813..3e2e3ee51cc9 100644
>> --- a/tools/testing/selftests/bpf/progs/test_sock_fields.c
>> +++ b/tools/testing/selftests/bpf/progs/test_sock_fields.c
>> @@ -114,7 +114,7 @@ static void tpcpy(struct bpf_tcp_sock *dst,
>>  
>>  #define RET_LOG() ({						\
>>  	linum = __LINE__;					\
>> -	bpf_map_update_elem(&linum_map, &linum_idx, &linum, BPF_NOEXIST);	\
>> +	bpf_map_update_elem(&linum_map, &linum_idx, &linum, BPF_ANY);	\
> Acked-by: Martin KaFai Lau <[email-masked]>

Thanks for the quick review.

I need to follow up with a v2. Was too quick to send this patch out by
itself. Now that the error reporting works, the test sock_fields tests
are failing on little- and big-endian.