netdev - Question about seccomp / bpf

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Message-ID: <CANn89iL_XLb5C-+DY5PRhneZDJv585xfbLtiEVc3-ejzNNXaVg@mail.gmail.com>
Date:   Wed, 8 May 2019 14:21:52 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        netdev <netdev@...r.kernel.org>
Subject: Question about seccomp / bpf

Hi Alexei and Daniel

I have a question about seccomp.

It seems that after this patch, seccomp no longer needs a helper
(seccomp_bpf_load())

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bd4cf0ed331a275e9bf5a49e6d0fd55dffc551b8

Are we detecting that a particular JIT code needs to call at least one
function from the kernel at all ?

If the filter contains self-contained code (no call, just inline
code), then we could use any room in whole vmalloc space,
not only from the modules (which is something like 2GB total on x86_64)

Thanks.