linux-kernel - Re: [RFC][PATCH] sysctl: Remove the sysctl system call

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Date:   Wed, 2 Oct 2019 09:31:01 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Kees Cook <keescook@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andi Kleen <andi@...stfloor.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Apelete Seketeli <apelete@...eteli.net>,
        Chee Nouk Phoon <cnphoon@...era.com>,
        Chris Zankel <chris@...kel.net>,
        Christian Ruppert <christian.ruppert@...lis.com>,
        Greg Ungerer <gerg@...inux.org>, Helge Deller <deller@....de>,
        Hongliang Tao <taohl@...ote.com>,
        Huacai Chen <chenhc@...ote.com>,
        Jonas Jensen <jonas.jensen@...il.com>,
        Josh Boyer <jwboyer@...il.com>, Jun Nie <jun.nie@...aro.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Ley Foon Tan <lftan@...era.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Max Filippov <jcmvbkbc@...il.com>,
        Olof Johansson <olof@...om.net>,
        Paul Burton <paul.burton@...s.com>,
        Phil Edworthy <phil.edworthy@...esas.com>,
        Pierrick Hascoet <pierrick.hascoet@...lis.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Roland Stigge <stigge@...com.de>,
        Vineet Gupta <vgupta@...opsys.com>
Subject: Re: [RFC][PATCH] sysctl: Remove the sysctl system call

On Wed, Oct 2, 2019 at 12:54 AM Eric W. Biederman <ebiederm@...ssion.com> wrote:
> Kees Cook <keescook@...omium.org> writes:
> > On Tue, Oct 01, 2019 at 01:36:32PM -0500, Eric W. Biederman wrote:
> >
> > I think you can actually take this further and remove (or at least
> > empty) the uapi/linux/sysctl.h file too.
>
> I copied everyone who had put this into a defconfig and I will wait a
> little more to see if anyone screams.  I think it is a safe guess that
> several of the affected configurations are dead (or at least
> unmaintained) as I received 17 bounces when copying everyone.

Looking at the arm defconfigs:

> arch/arm/configs/axm55xx_defconfig:CONFIG_SYSCTL_SYSCALL=y

No notable work on this platform since it got sold to Intel in 2014.
I think they still use it but not with mainline kernels that lack support
for most drivers and the later chips.

> arch/arm/configs/keystone_defconfig:CONFIG_SYSCTL_SYSCALL=y

Not that old either, but this hardware is mostly obsoleted by newer variants
that we support with the arm64 defconfig.

> arch/arm/configs/lpc32xx_defconfig:CONFIG_SYSCTL_SYSCALL=y
> arch/arm/configs/moxart_defconfig:CONFIG_SYSCTL_SYSCALL=y

Ancient hardware, but still in active use. These tend to have very little
RAM, but they both enable CONFIG_PROC_FS.

> arch/arm/configs/qcom_defconfig:CONFIG_SYSCTL_SYSCALL=y
> arch/arm/configs/zx_defconfig:CONFIG_SYSCTL_SYSCALL=y

These are for older Qualcomm and LG chips that tend to be used
with Android rather than the defconfig here. Maybe double-check
if the official android-common tree enables SYSCTL_SYSCALL.

      Arnd