linux-kernel - Re: [PATCH v3 seccomp 2/5] seccomp/cache: Add "emulator" to check if filter is constant allow

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Date:   Thu, 1 Oct 2020 06:28:32 -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>,
        kernel list <linux-kernel@...r.kernel.org>,
        Aleksa Sarai <cyphar@...har.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andy Lutomirski <luto@...capital.net>,
        David Laight <David.Laight@...lab.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>,
        Tycho Andersen <tycho@...ho.pizza>,
        Valentin Rothberg <vrothber@...hat.com>,
        Will Drewry <wad@...omium.org>
Subject: Re: [PATCH v3 seccomp 2/5] seccomp/cache: Add "emulator" to check if
 filter is constant allow

On Wed, Sep 30, 2020 at 5:24 PM Jann Horn <jannh@...gle.com> wrote:
> If you did the architecture enablement for X86 later in the series,
> you could move this part over into that patch, that'd be cleaner.

As in, patch 1: bitmap check logic. patch 2: emulator. patch 3: enable for x86?

> > + * Tis struct is ordered to minimize padding holes.
>
> I think this comment can probably go away, there isn't really much
> trickery around padding holes in the struct as it is now.

Oh right, I was trying the locks and adding bits to indicate if
certain arches are primed, then I undid that.

> > +                       set_bit(nr, bitmap);
>
> set_bit() is atomic, but since we only do this at filter setup, before
> the filter becomes globally visible, we don't need atomicity here. So
> this should probably use __set_bit() instead.

Right

YiFei Zhu