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

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Message-ID: <CAN+4W8gcquJRkZw+Knt=vqwR4YM8w5RbRNO-XyfE+DAyiEWANw@mail.gmail.com>
Date: Wed, 7 May 2025 10:14:02 +0100
From: Lorenz Bauer <lmb@...valent.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>, 
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 2/3] selftests: bpf: add a test for mmapable
 vmlinux BTF

On Tue, May 6, 2025 at 10:39 PM Andrii Nakryiko
<andrii.nakryiko@...il.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.

> > +       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.