netdev - Re: bpf indirect calls

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Date:   Sun, 27 Oct 2019 13:15:21 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     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>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: bpf indirect calls

Alexei Starovoitov <alexei.starovoitov@...il.com> writes:

> On Sun, Oct 20, 2019 at 3:58 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>> Great! I think it's probably more productive for everyone involved if I
>> just wait for you to get around to this, rather than try my own hand at
>> this. I'll go hash out the userspace management semantics of chain calls
>> in the meantime (using my kernel support patch), since that will surely
>> be needed anyway.
>
> No problem. Indirect calls are next on my todo list.
> Shouldn't take long.

Awesome!

> Right now I'm hacking accelerated kretprobes for tracing.
> I've shared first rough draft of patches with few folks and they
> quickly pointed out that the same logic can be used to
> create arbitrary call chains.
> To make kretprobe+bpf fast I'm replacing:
>   call foo
> with
>   prologue
>   capture args
>   call foo
>   capture return
>   call bpf_prog
>   epilogue
> That "call foo" can be anything. Including another bpf prog.
> Patches are too rough for public review.
> I hope to get them cleaned up by the end of next week.
>
> Jesper request to capture both struct xdp_md and return
> value after prog returns will be possible soon.
> xdpdump before and after xdp prog.. here I come :)

Sounds promising! Looking forward to seeing where this is going :)

-Toke