netdev - Re: [RFC PATCH 15/17] selftests/bpf: Add verifier tests for dequeue prog

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Message-ID: <CAP01T760my2iTzM5qsYvsZb6wvJP02k7BGOEOP-pHPPHEbH5Rg@mail.gmail.com>
Date:   Thu, 14 Jul 2022 08:45:11 +0200
From:   Kumar Kartikeya Dwivedi <memxor@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Mykola Lysenko <mykolal@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Freysteinn Alfredsson <freysteinn.alfredsson@....se>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Shuah Khan <shuah@...nel.org>
Subject: Re: [RFC PATCH 15/17] selftests/bpf: Add verifier tests for dequeue prog

On Thu, 14 Jul 2022 at 07:38, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
>
> On Wed, Jul 13, 2022 at 4:15 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
> >
> > From: Kumar Kartikeya Dwivedi <memxor@...il.com>
> >
> > Test various cases of direct packet access (proper range propagation,
> > comparison of packet pointers pointing into separate xdp_frames, and
> > correct invalidation on packet drop (so that multiple packet pointers
> > are usable safely in a dequeue program)).
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
> > Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> > ---
>
> Consider writing these tests as plain C BPF code and put them in
> test_progs, is there anything you can't express in C and thus requires
> test_verifier?

Not really, but in general I like test_verifier because it stays
immune to compiler shenanigans.
So going forward should test_verifier tests be avoided, and normal C
tests (using SEC("?...")) be preferred for these cases?

>
> >  tools/testing/selftests/bpf/test_verifier.c   |  29 +++-
> >  .../testing/selftests/bpf/verifier/dequeue.c  | 160 ++++++++++++++++++
> >  2 files changed, 180 insertions(+), 9 deletions(-)
> >  create mode 100644 tools/testing/selftests/bpf/verifier/dequeue.c
> >
>
> [...]