netdev - Re: [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF programs after each other

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Message-ID: <f9d5f717-51fe-7d03-6348-dbaf0b9db434@solarflare.com>
Date:   Tue, 15 Oct 2019 17:30:11 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>,
        "John Fastabend" <john.fastabend@...il.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Marek Majkowski <marek@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        Alan Maguire <alan.maguire@...cle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        "David Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF
 programs after each other

On 14/10/2019 19:48, Toke Høiland-Jørgensen wrote:
> So that will end up with a single monolithic BPF program being loaded
> (from the kernel PoV), right? That won't do; we want to be able to go
> back to the component programs, and manipulate them as separate kernel
> objects.
Why's that?  (Since it also applies to the static-linking PoC I'm
 putting together.)  What do you gain by having the components be
 kernel-visible?
(Bad analogy time: the kernel doesn't care about the .o files you
 linked together to make a userspace executable; any debugging you
 do on that relies on other userspace infrastructure — loading
 symbol tables into a debugger — to interpret things.)

-Ed