linux-kernel - Re: [PATCH 2/3] powerpc: Add system call table generation support

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Date:   Mon, 24 Sep 2018 22:59:59 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Firoz Khan <firoz.khan@...aro.org>
Cc:     linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, linuxram@...ibm.com,
        leitao@...ian.org, Boqun Feng <boqun.feng@...il.com>,
        gregkh <gregkh@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Marcin Juszkiewicz <marcin.juszkiewicz@...aro.org>
Subject: Re: [PATCH 2/3] powerpc: Add system call table generation support

On Tue, Sep 18, 2018 at 2:15 PM Firoz Khan <firoz.khan@...aro.org> wrote:
>
> On 14 September 2018 at 15:31, Arnd Bergmann <arnd@...db.de> wrote:
> > On Fri, Sep 14, 2018 at 10:33 AM Firoz Khan <firoz.khan@...aro.org> wrote:
> >
> >> ---
> >>  arch/powerpc/kernel/syscalls/Makefile       |  51 ++++
> >>  arch/powerpc/kernel/syscalls/syscall_32.tbl | 378 ++++++++++++++++++++++++++++
> >>  arch/powerpc/kernel/syscalls/syscall_64.tbl | 372 +++++++++++++++++++++++++++
> >>  arch/powerpc/kernel/syscalls/syscallhdr.sh  |  37 +++
> >>  arch/powerpc/kernel/syscalls/syscalltbl.sh  |  38 +++
> >
> > I think you should only need a single .tbl  input file here.
>
> Yes, we can do that way also.As I mentioned, it will add
> more complexity in the script.
>
>  The script has to be smart enough to parse the
> .tbl if we add more thing in the .tble file. It need more
> logic in the scripts. This is not common. So if you keep
> separate .tbl we can avoid this.

But all three existing architectures (x86, s390 and arm) already
have the capability to parse the table and generate different output
from that.

> ABI flag is serving *nothing* in all other architecture including
> SPARC.

If you don't use it in sparc, I think that's a bug, see e.g.

#ifdef __32bit_syscall_numbers__
#define __NR_setresuid32        108 /* Linux Specific, sigvec under
SunOS          */
#else
#define __NR_setresuid          108 /* Linux Specific, sigvec under
SunOS          */
#endif

> But as I told in the cover letter, I followed x86/arm/
> s390 architecture's system table generation implementation.
> They are keeping ABI flag. In our case we can delete this
> flag completely from all architectures.
>
> Most of the architecture these 32/64 similarity is absent.
> So it would be better keep separate files to maintain a
> generic script across all architecture.

There are a couple of architectures that definitely need it:
ARM for oabi, x86 for x32, s390, parisc and sparc for compat,
asm-generic for compat, powerpc for compat and spu,
and arm64 if we want to share the arm32 syscall table
for compat mode later.

      Arnd