linux-kernel - Re: [PATCH 3/6] seccomp: Implement constant action bitmaps

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Message-ID: <CABqSeAR+DO3=Gt1KAAYKTJd7k07sH+aQCkofXxm7nX2TXh=w6A@mail.gmail.com>
Date:   Thu, 24 Sep 2020 03:22:31 -0500
From:   YiFei Zhu <zhuyifei1999@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Jann Horn <jannh@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Will Drewry <wad@...omium.org>, bpf <bpf@...r.kernel.org>,
        YiFei Zhu <yifeifz2@...inois.edu>,
        Linux API <linux-api@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Hubertus Franke <frankeh@...ibm.com>,
        Andy Lutomirski <luto@...capital.net>,
        Valentin Rothberg <vrothber@...hat.com>,
        Dimitrios Skarlatos <dskarlat@...cmu.edu>,
        Jack Chen <jianyan2@...inois.edu>,
        Josep Torrellas <torrella@...inois.edu>,
        Tianyin Xu <tyxu@...inois.edu>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/6] seccomp: Implement constant action bitmaps

On Thu, Sep 24, 2020 at 3:15 AM Kees Cook <keescook@...omium.org> wrote:
> I was trying to be helpful: you hadn't seen the RFC, and it was missing
> the emulator piece, which I wanted to be small, so I put got it out the
> door today. I didn't want you to think you needed to port the larger
> emulator over, for example.

There's no architecture-dependent code in the emulator. It just has to
iterate through all the arch numbers. So I don't know what you are
referring to by "port ... over".
The logic is simple. If the emulator determines the filter must be an
allow for a given arch / syscall pair, then it is "cached by bitmap".

> I'm open to ideas, but I want to have a non-optional performance
> improvement as the first step. :)

How about "performance improvement by default"? It's not like most end
users / distros would turn off something that's enabled by default
when they upgrade to a new kernel.

YiFei Zhu