netdev - Re: [PATCH v3 bpf-next] bpf: make verifier log more relevant by default

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Date:   Thu, 5 Nov 2020 13:22:12 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Benc <jbenc@...hat.com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v3 bpf-next] bpf: make verifier log more relevant by default

On Thu, Nov 5, 2020 at 8:02 AM Jiri Benc <jbenc@...hat.com> wrote:
>
> On Thu, 23 Apr 2020 12:58:50 -0700, Andrii Nakryiko wrote:
> > To make BPF verifier verbose log more releavant and easier to use to debug
> > verification failures, "pop" parts of log that were successfully verified.
> > This has effect of leaving only verifier logs that correspond to code branches
> > that lead to verification failure, which in practice should result in much
> > shorter and more relevant verifier log dumps. This behavior is made the
> > default behavior and can be overriden to do exhaustive logging by specifying
> > BPF_LOG_LEVEL2 log level.
>
> This patch broke the test_offload.py selftest:
>
> [...]
> Test TC offloads work...
> FAIL: Missing or incorrect message from netdevsim in verifier log
> [...]
>
> The selftest expects to receive "[netdevsim] Hello from netdevsim!" in
> the log (coming from nsim_bpf_verify_insn) but that part of the log is
> cleared by bpf_vlog_reset added by this patch.

Should we just drop check_verifier_log() checks?

>
> How can this be fixed? The log level 1 comes from the "verbose" keyword
> passed to tc, I don't think it should be increased to 2.
>
> On a related note, the selftest had to start failing after this commit.
> It's a bit surprising it did not get caught, is there a bug somewhere
> in the test matrix?

test_progs is the only test runner that's run continuously on every
patch. libbpf CI also runs test_maps and test_verifier. All the other
test binaries/scripts rely on humans to not forget about them. Which
works so-so, as you can see :)

>
> Thanks,
>
>  Jiri
>