linux-kernel - Re: [PATCH 15/15] arch: add pkey and rseq syscall numbers everywhere

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Message-ID: <CAK8P3a1Xb4z-mbhBTPZ0Cpy0Hy_s2wwT-8UG9yO6AGbUTjdkyw@mail.gmail.com>
Date:   Tue, 15 Jan 2019 15:47:14 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     y2038 Mailman List <y2038@...ts.linaro.org>,
        Linux API <linux-api@...r.kernel.org>,
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Subject: Re: [PATCH 15/15] arch: add pkey and rseq syscall numbers everywhere

On Tue, Jan 15, 2019 at 12:52 PM Russell King - ARM Linux admin
<linux@...linux.org.uk> wrote:
>
> On Thu, Jan 10, 2019 at 05:24:35PM +0100, Arnd Bergmann wrote:
> > Most architectures define system call numbers for the rseq and pkey system
> > calls, even when they don't support the features, and perhaps never will.
> >
> > Only a few architectures are missing these, so just define them anyway
> > for consistency. If we decide to add them later to one of these, the
> > system call numbers won't get out of sync then.
>
> I was lambasted for adding the pkey syscalls for 32-bit ARM in 2016,
> which will probably never support it.  Why has the attitude towards
> this kind of thing now apparently become acceptable?

I was (and still am) a bit unsure about this one. A number of architectures
added the numbers that won't ever support them, but I wasn't sure if
any of those that didn't add them might need it later.

I tried to just go by the rule that anything that we list in
asm-generic/unistd.h
is probably important enough that we want to list it everywhere, even if
that includes a couple that we end up being rather architecture specific.

I'm happy to drop this patch if you or others feel that we're better off
without it though.

      Arnd