Re: [PATCH bpf-next 1/2] selftests/bpf: Move verifier failure tests out of test_global_percpu_data

[Leon Hwang]

On 2026/9/7 13:46, Thiébaud Weksteen wrote:
> On Fri, Sep 4, 2026 at 4:07 PM Leon Hwang <leon.hwang@xxxxxxxxx> wrote:
>>
>> On 4/9/26 11:19, Thiébaud Weksteen wrote:
>>> Commit 4c9241bd731a ("selftests/bpf: Add tests to verify global percpu
>>> data") added test_global_percpu_data.c to LSKELS_EXTRA. Later, in commit
>>> 1ed2294b31fc ("selftests/bpf: Test verifier log for global percpu data")
>>> two verifier failure tests were added (verifier_strncmp and
>>> verifier_snprintf), both marked as non-autoload (SEC("?kprobe")).
>>>
>>> When bpftool generates light skeletons, non-autoloaded programs are
>>> skipped during loading, causing the loader program to store subsequent
>>> program FDs into incorrect skeleton struct fields (e.g. dump_percpu_data's
>>> FD was stored into verifier_strncmp's descriptor).
>>
>> IIUC, patch 2 will fix the issue totally.
>>
>> Better to add a subtest to verify both the issue and the fix?
> 
> Thanks for the review. That's right, patch 2 will fix the issue:
> bpftool will fail to build any program that is set up that way. That's
> why patch 1 is necessary; otherwise, the existing test would fail.
> 
> Just checking your suggestion: what I can do is add a new test to make
> sure that dump_percpu_data is set up as expected (fd > 0). I can write
> a new test_global_percpu_data_iter_lskel, that is similar to
> test_global_percpu_data_iter, but for lskel?
> 
> I can also write a test to ensure that bpftool fails when light
> skeletons are set up with autoload=false?
> 

imo, the rejection of autoload=false prog when generating light skeleton
is not friendly for users. Users should not care about mixing
autoload=false progs with autoload=true progs, even for light skeletons.

The users-friendly way is to skip those autoload=false progs when
generating light skeletons.

So, this is a bpftool issue. A selftest is unnecessary. You can verify
both the issue and the fix manually. Probably, paste the verification
result in the patch message.

Thanks,
Leon