netdev - Re: [PATCH bpf-next v3 00/10] Support kernel module function calls from eBPF

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Date:   Wed, 15 Sep 2021 23:33:01 +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 v3 00/10] Support kernel module function calls
 from eBPF

On Wed, Sep 15, 2021 at 09:34:21PM IST, Andrii Nakryiko wrote:
> On Tue, Sep 14, 2021 at 10:09 PM 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:
> > ----------
> > v2 -> v3:
> > v2: https://lore.kernel.org/bpf/20210914123750.460750-1-memxor@gmail.com
> >
> >  * Fix issues pointed out by Kernel Test Robot
> >  * Fix find_kfunc_desc to also take offset into consideration when comparing
>
> See [0]:
>
>
>   [  444.075332] mod kfunc i=42
>   [  444.075383] mod kfunc i=42
>   [  444.075522] mod kfunc i=42
>   [  444.075578] mod kfunc i=42
>   [  444.075631] mod kfunc i=42
>   [  444.075683] mod kfunc i=42
>   [  444.075735] mod kfunc i=42
>   [  444.0
> This step has been truncated due to its large size. Download the full
> logs from the
> menu once the workflow run has completed.
>
>   [0] https://github.com/kernel-patches/bpf/runs/3606513281?check_suite_focus=true
>

I'll change it to not use printk in the next spin (maybe just set a variable).
This probably blew up because of parallel test_progs stuff, since it would be
called for each sys_enter as long the raw_tp prog is attached.

--
Kartikeya