Re: [PATCH bpf-next v3 2/3] selftests: bpf: add a test for mmapable vmlinux BTF

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Wed, May 7, 2025 at 2:14 AM Lorenz Bauer <lmb@isovalent.com> wrote:
>
> On Tue, May 6, 2025 at 10:39 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
>
> > > +       raw_data = mmap(NULL, end, PROT_READ, MAP_PRIVATE, fd, 0);
> > > +       if (!ASSERT_NEQ(raw_data, MAP_FAILED, "mmap_btf"))
> >
> > ASSERT_OK_PTR()?
>
> Don't think that mmap follows libbpf_get_error conventions? I'd keep
> it as it is.

ASSERT_OK_PTR() isn't libbpf specific (and libbpf is actually
returning a NULL or valid pointer for all public APIs, since libbpf
1.0). But if you look at the implementation, "an OK" pointer is a
non-NULL pointer that is also not a small negative value. NULL is a
bad pointer, -1 (MAP_FAILED) is a bad pointer, and so on. So it's a
pretty universal check for anything pointer-related. Please do use
OK_PTR, it's semantically better in tests

>
> > > +       btf = btf__new_split(raw_data, btf_size, base);
> > > +       if (!ASSERT_NEQ(btf, NULL, "parse_btf"))
> >
> > ASSERT_OK_PTR()
>
> Ack.
>
> > Do you intend to add more subtests? if not, why even using a subtest structure
>
> The original intention was to add kmod support, but that didn't pan
> out, see my discussion with Alexei. I can drop the subtest if you
> want, but I'd probably keep the helper as it is.

yeah, let's drop the subtest, it's a bit easier to work with
non-subtest tests, IMO