linux-kernel - Re: [RFC PATCH seccomp 2/2] seccomp/cache: Cache filter results that allow syscalls

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Message-ID: <CABqSeAQDpJZdAD42myca=3BAGAJ9VyDjvEiXfcH+p3m4eo_vBw@mail.gmail.com>
Date:   Mon, 21 Sep 2020 18:08:00 -0500
From:   YiFei Zhu <zhuyifei1999@...il.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     Linux Containers <containers@...ts.linux-foundation.org>,
        YiFei Zhu <yifeifz2@...inois.edu>, bpf <bpf@...r.kernel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Dimitrios Skarlatos <dskarlat@...cmu.edu>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Hubertus Franke <frankeh@...ibm.com>,
        Jack Chen <jianyan2@...inois.edu>,
        Josep Torrellas <torrella@...inois.edu>,
        Kees Cook <keescook@...omium.org>,
        Tianyin Xu <tyxu@...inois.edu>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Valentin Rothberg <vrothber@...hat.com>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        Aleksa Sarai <cyphar@...har.com>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH seccomp 2/2] seccomp/cache: Cache filter results that
 allow syscalls

On Mon, Sep 21, 2020 at 5:58 PM Jann Horn <jannh@...gle.com> wrote:
> > I do agree that an immutable bitmask is faster and easier to reason
> > about its correctness. However, I did not find the "code to statically
> > evaluate the filter for all syscall numbers" while reading seccomp.c.
> > Would you give me a pointer to that and I will see how to best make
> > use of it?
>
> I'm talking about the code you're adding in the other patch ("[RFC
> PATCH seccomp 1/2] seccomp/cache: Add "emulator" to check if filter is
> arg-dependent"). Sorry, that was a bit unclear.

I see, building an immutable accept bitmask when preparing and then
just use that when running it. I guess if the arch number issue is
resolved this should be more doable. Will do.

YiFei Zhu