Re: Failure in test_local_storage at bpf-next

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: KP Singh <kpsingh@chromium.org>, bpf <bpf@vger.kernel.org>,
	Andrii Nakryiko <andriin@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <ast@kernel.org>
Subject: Re: Failure in test_local_storage at bpf-next
Date: Tue, 6 Oct 2020 21:44:02 -0700	[thread overview]
Message-ID: <CAEf4BzZ5WOwAkfqXpJCujkrcN-8DL2UvtiNpSiELBT7z99h5cg@mail.gmail.com> (raw)
In-Reply-To: <71e1203f-5864-f86d-e587-67d92183b89b@fb.com>

On Tue, Oct 6, 2020 at 9:31 PM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 10/6/20 6:23 PM, Andrii Nakryiko wrote:
> > On Tue, Oct 6, 2020 at 5:31 PM KP Singh <kpsingh@chromium.org> wrote:
> >>
> >> I noticed that test_local_storage is broken due to a BTF error at
> >> bpf-next [67ed375530e2 ("samples: bpf: Driver interrupt statistics in
> >> xdpsock")]
> >>
> >> ./test_progs -t test_local_storage
> >> libbpf: prog 'socket_post_create': relo #0: parsing [28] struct socket + 0:0.1 2
> >
> > This line is truncated, btw, please make sure you post the entire
> > output next time.
> >
> > But, this seems like a bug in Clang, it produced invalid access index
> > string "0:0.1", there shouldn't be any other separator except ':' in
> > those strings.
> >
> > Yonghong, can you please take a look? This seems to be a very recent
> > regression, I had to update to
> > 6c7d713cf5d9bb188f1e73452a256386f0288bf7 sha from not-too-outdated
> > version to repro this.
>
> Sorry. This indeed is a llvm regression. The guilty patch is
> https://reviews.llvm.org/D88855 which adds NPM (new pass manager)
> support for BPF. The patch just merged this morning, thanks for catching
> the bug so fast. Since NPM is not used by default and the code
> refactoring looks okay, so I did not run selftests. But, yah, it does
> change some semantics of the code...
>
> I just put a fix at https://reviews.llvm.org/D88942.
> Hopefully to merge soon.

No worries, thanks for a quick fix!

>
> >
> >> libbpf: prog 'socket_post_create': relo #0: failed to relocate: -22
> >> libbpf: failed to perform CO-RE relocations: -22
> >> libbpf: failed to load object 'local_storage'
> >> libbpf: failed to load BPF skeleton 'local_storage': -22
> >> test_test_local_storage:FAIL:skel_load lsm skeleton failed
> >>
> >> by changing it to use vmlinux.h with:
> >>
> >
> > [...]
> >
> >>
> >> clang --version
> >> clang version 12.0.0 (https://github.com/llvm/llvm-project.git
> >> 6c7d713cf5d9bb188f1e73452a256386f0288bf7)
> >> Target: x86_64-unknown-linux-gnu
> >> Thread model: posix
> >>
> >> pahole --version
> >> v1.18
> >>
> >> This error goes away if I comment out the lsm/socket_post_create or
> >> the lsm/socket_bind which makes me think that something in
> >> bpf_core_apply_relo does not like two programs in the same object
> >> having the same BTF type in its signature (but this just a guess, I
> >> did not investigate more).  I was wondering if anyone has any ideas
> >> what could be going on here.
> >>
> >> PS: While working on task local storage, I noted that some of the
> >> checks in this test were buggy and will send a patch to fix them as
> >> well.
> >>
> >> - KP