netdev - Re: [PATCH bpf-next v4 00/11] Support kernel module function calls from eBPF

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Message-ID: <20210921045515.dpn64ok5sd7ezexp@apollo.localdomain>
Date:   Tue, 21 Sep 2021 10:25:15 +0530
From:   Kumar Kartikeya Dwivedi <memxor@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 00/11] Support kernel module function calls
 from eBPF

On Tue, Sep 21, 2021 at 05:59:22AM IST, Andrii Nakryiko wrote:
> On Mon, Sep 20, 2021 at 7:15 AM Kumar Kartikeya Dwivedi
> <memxor@...il.com> wrote:
> >
> > This set enables kernel module function calls, and also modifies verifier logic
> > to permit invalid kernel function calls as long as they are pruned as part of
> > dead code elimination. This is done to provide better runtime portability for
> > BPF objects, which can conditionally disable parts of code that are pruned later
> > by the verifier (e.g. const volatile vars, kconfig options). libbpf
> > modifications are made along with kernel changes to support module function
> > calls. The set includes gen_loader support for emitting kfunc relocations.
> >
> > It also converts TCP congestion control objects to use the module kfunc support
> > instead of relying on IS_BUILTIN ifdef.
> >
> > Changelog:
> > ----------
> > v3 -> v4
>
> Please use vmtest.sh locally to test everything. That should help to
> avoid breaking our CI ([0]):
>

I'll look into it. There were some problems getting it to run on Arch and
Fedora, so I instead tested in my own VM (GLIBC_2.33 not found).

Surprisingly, everything passed when I ran it before sending. e.g. I still
get this for the two failing tests in CI.

[root@(none) bpf]# ./test_progs -t ksyms_module_libbpf
#66 ksyms_module_libbpf:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
[root@(none) bpf]# ./test_progs -t module_attach
#81 module_attach:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

--
Kartikeya