Re: selftest/bpf/test_verifier_log fails on v5.11-rc5

From: Ondrej Mosnacek <omosnace@redhat.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Moore <paul@paul-moore.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Jiri Olsa <jolsa@kernel.org>, Andrii Nakryiko <andrii@kernel.org>,
	bpf <bpf@vger.kernel.org>
Subject: Re: selftest/bpf/test_verifier_log fails on v5.11-rc5
Date: Mon, 1 Feb 2021 23:43:26 +0100	[thread overview]
Message-ID: <CAFqZXNsjzQ-2x4-szW5pBg77bzSK-RmwPvQSN+UaxJXqqZ_2qA@mail.gmail.com> (raw)
In-Reply-To: <YBhjOaoV2NqW3jFI@krava>

On Mon, Feb 1, 2021 at 9:23 PM Jiri Olsa <jolsa@redhat.com> wrote:
> On Mon, Feb 01, 2021 at 03:50:22PM +0100, Jiri Olsa wrote:
>
> SNIP
>
> > > >
> > > > with Arnaldo's fixes I see less struct duplications,
> > > > but still there's some
> > > >
> > > > >
> > > > > I uploaded the build log from linking part to:
> > > > >   http://people.redhat.com/~jolsa/build.out.gz
> > > >
> > > > however looks like we don't handle DW_FORM_implicit_const
> > > > when counting the byte offset.. it was used for some struct
> > > > members in my vmlinux, so we got zero for byte offset and
> > > > that created another unique struct
> > > >
> > > > with patch below I no longer see any struct duplication,
> > > > also test_verifier_log is working for me, but I could
> > > > not reproduce the error before
> > > >
> > > > I'll post full dwarves patch after some more testing
> > > >
> > > > also I wonder we could somehow use btf_check_all_metas
> > > > from kernel after we build BTF data, that'd help to catch
> > > > this earlier/easier ;-) I'll check on this
> > >
> > > Seems like a good idea indeed :-)
> > >
> > > I'm applying the patch below with your Signed-off-by, etc, ok?
> >
> > ok, thanks
>
> Paul, Ondrej,
>
> I put all the recent fixes and made a scratch build:
>   https://koji.fedoraproject.org/koji/taskinfo?taskID=61049457
>
> if you have a chance to test and check your issue was resolved,
> that'd be great

I just built the current master branch of dwarves (d783117162c0, which
includes Jirka's patch) [1] in COPR [2] and then rebuilt the kernel
with it [3]. With the new dwarves, the issue seems to be fixed -
/sys/kernel/btf/vmlinux is back to ~4MB and the selinux-testsuite BPF
subtest passes.

Thanks everyone for getting to the bottom of this! Hoping to see an
updated dwarves in rawhide soon ;)

[1] https://github.com/acmel/dwarves/
[2] https://copr.fedorainfracloud.org/coprs/omos/kernel-btf-test/build/1930103/
[3] https://copr.fedorainfracloud.org/coprs/omos/kernel-btf-test/build/1930104/

--
Ondrej Mosnacek
Software Engineer, Platform Security - SELinux kernel
Red Hat, Inc.