Re: [PATCH bpf-next v2 15/18] libbpf: add skip_invalid and attach_tracing for tracing_multi

[Menglong Dong <menglong.dong@linux.dev>]

On Wednesday, July 16, 2025 1:23 AM Andrii Nakryiko <andrii.nakryiko@gmail.com> write:
[......]
> 
> The right answer here is you need to know what's attachable and what's
> not, instead of just ignoring attachment failures somewhere deep
> inside libbpf API. Filter and check before you try to attach. There is
> /sys/kernel/tracing/available_filter_functions and some similar
> blacklist file, consult that, filter out stuff that's not attachable.
> 
> We won't be adding libbpf APIs just to make some selftests easier to
> write by being sloppy.
> 
> >
> > This should be a common use case. And let me do more research to see if
> > we can do such filter out of the libbpf.
> 
> I have similar issues with retsnoop ([0]) and do just fine without
> abusing libbpf API.
> 
>   [0] https://github.com/anakryiko/retsnoop/blob/master/src/mass_attacher.c#L749

Thank you for the reference, and I think it will work to do such
filtering in the selftests.