netdev - Re: [PATCH bpf-next v8 00/10] Introduce unstable CT lookup helpers

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Date:   Sat, 19 Feb 2022 17:13:20 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexander Egorenkov <egorenar@...ux.ibm.com>
Cc:     Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Alexander.Egorenkov@....com, Andrii Nakryiko <andrii@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>, bpf <bpf@...r.kernel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Florian Westphal <fw@...len.de>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        john fastabend <john.fastabend@...il.com>,
        Martin Lau <kafai@...com>,
        Maxim Mikityanskiy <maximmi@...dia.com>,
        Networking <netdev@...r.kernel.org>,
        netfilter-devel@...r.kernel.org,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Song Liu <songliubraving@...com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Yonghong Song <yhs@...com>
Subject: Re: [PATCH bpf-next v8 00/10] Introduce unstable CT lookup helpers

On Fri, Feb 18, 2022 at 11:39 PM Alexander Egorenkov
<egorenar@...ux.ibm.com> wrote:
>
>
> Hi Kartikeya,
>
> sorry if i wasn't clear in my first message but just to be sure
> we have no misunderstandings :)
>
> .BTF sections work on s390x with linux-next and nf_conntrack as well if
> the corresponding .BTF section is a part of the kernel module itself.
> I tested it myself by building a linux-next kernel and testing it with a
> KVM guest, i'm able to load nf_conntrack and it works.
>
> In contrast, in the case where the corresponding .BTF section is separate
> from the kernel module nf_conntrack, it fails with the message i
> provided in the first email.
>
> Therefore, my question is, does BTF for kernel modules work if the
> corresponding BTF section is NOT a part of the kernel module but instead
> is stored within the corresponding debuginfo file
> /usr/lib/debug/lib/modules/*/kernel/net/netfilter/nf_conntrack.ko.debug ?

No, it doesn't. .BTF has to be part of the module's .ko ELF file.
DWARF can be stripped out, it's only needed for generating BTF during
the build process.

It actually would be great to have an option to generate BTF without
leaving any DWARF, but that's a separate topic.

>
> Thanks
> Regards
> Alex
>
>
>