linux-kernel - Re: [PATCH seccomp 3/8] powerpc: Enable seccomp architecture tracking

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Message-ID: <87ft5ot56z.fsf@mpe.ellerman.id.au>
Date:   Thu, 05 Nov 2020 22:26:44 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     YiFei Zhu <zhuyifei1999@...il.com>
Cc:     Linux Containers <containers@...ts.linux-foundation.org>,
        linux-sh@...r.kernel.org, Tobin Feldman-Fitzthum <tobin@....com>,
        Hubertus Franke <frankeh@...ibm.com>,
        Jack Chen <jianyan2@...inois.edu>,
        linux-riscv@...ts.infradead.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        linux-s390@...r.kernel.org, YiFei Zhu <yifeifz2@...inois.edu>,
        linux-csky@...r.kernel.org, Tianyin Xu <tyxu@...inois.edu>,
        linux-xtensa@...ux-xtensa.org, Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>,
        Valentin Rothberg <vrothber@...hat.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Josep Torrellas <torrella@...inois.edu>,
        Will Drewry <wad@...omium.org>, linux-parisc@...r.kernel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Dimitrios Skarlatos <dskarlat@...cmu.edu>,
        David Laight <David.Laight@...lab.com>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        linuxppc-dev@...ts.ozlabs.org, Tycho Andersen <tycho@...ho.pizza>
Subject: Re: [PATCH seccomp 3/8] powerpc: Enable seccomp architecture tracking

YiFei Zhu <zhuyifei1999@...il.com> writes:
> On Wed, Nov 4, 2020 at 4:22 AM Michael Ellerman <mpe@...erman.id.au> wrote:
>> > +#ifdef __LITTLE_ENDIAN__
>>
>> As Kees mentioned this should (must?!) match the configured endian.
>>
>> But I think it would still be better to use the CONFIG symbol, which is
>> CONFIG_CPU_LITTLE_ENDIAN.
>
> My attempt here is to be consistent with asm/syscall.h
> syscall_get_arch [1]. Would it make sense to change that to
> CONFIG_CPU_LITTLE_ENDIAN then?
>
> [1] https://elixir.bootlin.com/linux/latest/source/arch/powerpc/include/asm/syscall.h#L116

Looking across the tree with have thousands of usages of
__LITTLE_ENDIAN__, so it's probably not worth converting to
CONFIG_CPU_LITTLE_ENDIAN.

>> > +# define SECCOMP_ARCH_NATIVE         (AUDIT_ARCH_PPC64 | __SECCOMP_ARCH_LE)
>>
>> You use __SECCOMP_ARCH_LE there, but previously you only defined
>> __SECCOMP_ARCH_LE_BIT.
>>
>> Is there some magic somewhere that defines __SECCOMP_ARCH_LE based on
>> __SECCOMP_ARCH_LE_BIT ?
>
> Oops, my bad here.

OK :)

>> > +# define SECCOMP_ARCH_NATIVE_NR              NR_syscalls
>> > +# define SECCOMP_ARCH_NATIVE_NAME    "ppc64"
>>
>> What's the name used for?
>
> This is used in the last patch in this series to report in procfs the
> name of each architecture tracked by the bitmap cache.

OK, yeah I think it would be better if the matched the uname -m values.

>> Usually we use "ppc64" for 64-bit big endian and "ppc64le" for 64-bit
>> little endian.
>>
>> And usually we use "ppc" for 32-bit.
>
> Ok.


cheers