linux-kernel - Re: [PATCH] bpf: validate bpf_func when BPF

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Date:   Wed, 11 Sep 2019 14:07:38 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        Yonghong Song <yhs@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kees Cook <keescook@...omium.org>, Martin Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH] bpf: validate bpf_func when BPF_JIT is enabled

On Wed, Sep 11, 2019 at 5:09 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> Björn Töpel <bjorn.topel@...el.com> writes:
> > I ran the "xdp_rxq_info" sample with and without Sami's patch:
>
> Thanks for doing this!

Yes, thanks for testing this Björn!

> Or (1/22998700 - 1/23923874) * 10**9 == 1.7 nanoseconds of overhead.
>
> I guess that is not *too* bad; but it's still chipping away at
> performance; anything we could do to lower the overhead?

The check is already rather minimal, but I could move this to a static
inline function to help ensure the compiler doesn't generate an
additional function call for this. I'm also fine with gating this
behind a separate config option, but I'm not sure if that's worth it.
Any thoughts?

Sami