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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Wed, 2 Oct 2019 09:31:01 +0200
Message-ID: <CAK8P3a1zLATC7rzYxSpAK-z=NJ1rw7-3ZgHqCOJUUf6b9HwK1A@mail.gmail.com>
Subject: Re: [RFC][PATCH] sysctl: Remove the sysctl system call
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Kees Cook <keescook@chromium.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
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        Cong Wang <xiyou.wangcong@gmail.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
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        Chee Nouk Phoon <cnphoon@altera.com>,
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        Greg Ungerer <gerg@uclinux.org>, Helge Deller <deller@gmx.de>,
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On Wed, Oct 2, 2019 at 12:54 AM Eric W. Biederman <ebiederm@xmission.com> wrote:
> Kees Cook <keescook@chromium.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