linux-kernel - Re: [PATCH v5 seccomp 5/5] seccomp/cache: Report cache data through /proc/pid/seccomp

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Date:   Thu, 17 Dec 2020 12:34:39 -0600
From:   YiFei Zhu <zhuyifei1999@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Containers <containers@...ts.linux-foundation.org>,
        YiFei Zhu <yifeifz2@...inois.edu>, bpf <bpf@...r.kernel.org>,
        Linux Kernel Mailing 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>,
        Jann Horn <jannh@...gle.com>,
        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 v5 seccomp 5/5] seccomp/cache: Report cache data through /proc/pid/seccomp_cache

On Thu, Dec 17, 2020 at 6:14 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> Should there be a dependency on SECCOMP_ARCH_NATIVE?
> Should all architectures that implement seccomp have this?
>
> E.g. mips does select HAVE_ARCH_SECCOMP_FILTER, but doesn't
> have SECCOMP_ARCH_NATIVE?
>
> (noticed with preliminary out-of-tree seccomp implementation for m68k,
>  which doesn't have SECCOMP_ARCH_NATIVE

Hi Geert

You are correct. This specific patch in this series was not applied,
and this was addressed in a follow up patch series [1]. MIPS does not
define SECCOMP_ARCH_NATIVE because the bitmap expects syscall numbers
to start from 0, whereas MIPS does not (defines
CONFIG_HAVE_SPARSE_SYSCALL_NR). The follow up patch makes it so that
any arch with HAVE_SPARSE_SYSCALL_NR (currently just MIPS) cannot have
CONFIG_SECCOMP_CACHE_DEBUG on, by the depend on clause.

I see that you are doing an out of tree seccomp implementation for
m68k. Assuming unchanged arch/xtensa/include/asm/syscall.h, something
like this to arch/m68k/include/asm/seccomp.h should make it work:

#define SECCOMP_ARCH_NATIVE        AUDIT_ARCH_M68K
#define SECCOMP_ARCH_NATIVE_NR        NR_syscalls
#define SECCOMP_ARCH_NATIVE_NAME    "m68k"

If the file does not exist already, arch/xtensa/include/asm/seccomp.h
is a good example of how the file should look like, and remember to
remove `generic-y += seccomp.h` from arch/m68k/include/asm/Kbuild.

[1] https://lore.kernel.org/lkml/cover.1605101222.git.yifeifz2@illinois.edu/T/

YiFei Zhu