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

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Message-ID: <CAEf4BzaWuGnbduumDA1k=5Cm5nt0wfJtxb0yeyNZ+=PxFCP61Q@mail.gmail.com>
Date:   Mon, 27 Apr 2020 21:55:12 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Network Development <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 Sun, Apr 26, 2020 at 9:58 AM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Thu, Apr 23, 2020 at 1:04 PM Andrii Nakryiko <andriin@...com> 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.
> ...
> > On success, verbose log will only have a summary of number of processed
> > instructions, etc, but no branch tracing log. Having just a last succesful
> > branch tracing seemed weird and confusing. Having small and clean summary log
> > in success case seems quite logical and nice, though.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
>
> I think the behavior described in the last paragraph could be
> surprising to some folks who expected to see the verifier log for
> successfully loaded progs.
> May be worth mentioning this in Documentation/networking/filter.txt ?
> That doc needs some cleanup too.

Sure, I'll do a follow-up patch to mention this.

>
> Applied. Thanks