linux-kernel - Re: [PATCH 2/2] arch: add pidfd and io

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Message-ID: <CAK8P3a1dVLdL_oM8iCGP1R0SG=4BrrsPSaTare5NN5WLxJb_Uw@mail.gmail.com>
Date:   Tue, 26 Mar 2019 09:40:57 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Paul Burton <paul.burton@...s.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michal Simek <monstr@...str.eu>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        "James E . J . Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
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        Firoz Khan <firoz.khan@...aro.org>,
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        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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Subject: Re: [PATCH 2/2] arch: add pidfd and io_uring syscalls everywhere

On Mon, Mar 25, 2019 at 6:37 PM Paul Burton <paul.burton@...s.com> wrote:
> On Mon, Mar 25, 2019 at 03:47:37PM +0100, Arnd Bergmann wrote:
> > Add the io_uring and pidfd_send_signal system calls to all architectures.
> >
> > These system calls are designed to handle both native and compat tasks,
> > so all entries are the same across architectures, only arm-compat and
> > the generic tale still use an old format.
> >
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > ---
> >%
> > diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
> > index c85502e67b44..c4a49f7d57bb 100644
> > --- a/arch/mips/kernel/syscalls/syscall_n64.tbl
> > +++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
> > @@ -338,3 +338,7 @@
> >  327  n64     rseq                            sys_rseq
> >  328  n64     io_pgetevents                   sys_io_pgetevents
> >  # 329 through 423 are reserved to sync up with other architectures
> > +424  common  pidfd_send_signal               sys_pidfd_send_signal
> > +425  common  io_uring_setup                  sys_io_uring_setup
> > +426  common  io_uring_enter                  sys_io_uring_enter
> > +427  common  io_uring_register               sys_io_uring_register
>
> Shouldn't these declare the ABI as "n64"?
>
> I don't see anywhere that it would actually change the generated code,
> but a comment at the top of the file says that every entry should use
> "n64" and so far they all do. Did you have something else in mind here?

You are right, the use of 'common' here is unintentional but harmless,
and I should have used 'n64' here.

We may decide to do things differently in the future, i.e. we could
have just a single global file for newly added system calls once
it turns out that the tables are consistent across all architectures,
but I'd probably go on with the separate identical entries for a bit
before changing that.

     Arnd