linux-kernel - Re: [PATCH v3 5/6] parisc: wire up rseq system call

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Date:   Mon, 8 Oct 2018 14:25:16 +0530
From:   Firoz Khan <firoz.khan@...aro.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Helge Deller <deller@....de>, linux-parisc@...r.kernel.org,
        "James E . J . Bottomley" <jejb@...isc-linux.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        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>,
        Arnd Bergmann <arnd@...db.de>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Marcin Juszkiewicz <marcin.juszkiewicz@...aro.org>
Subject: Re: [PATCH v3 5/6] parisc: wire up rseq system call

Hi Geert,

On Mon, 8 Oct 2018 at 13:53, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Firoz,
>
> On Mon, Oct 8, 2018 at 8:49 AM Firoz Khan <firoz.khan@...aro.org> wrote:
> > On Mon, 8 Oct 2018 at 11:36, Helge Deller <deller@....de> wrote:
> > > On 08.10.2018 07:52, Firoz Khan wrote:
> > > > On Mon, 8 Oct 2018 at 11:11, Helge Deller <deller@....de> wrote:
> > > >> On 08.10.2018 07:16, Firoz Khan wrote:
> > > >>> Signed-off-by: Firoz Khan <firoz.khan@...aro.org>
> > > >>> ---
> > > >>>  arch/parisc/kernel/syscalls/syscall.tbl | 3 ++-
> > > >>>  1 file changed, 2 insertions(+), 1 deletion(-)
> > > >>>
> > > >>> diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
> > > >>> index 4e85293..4334bb7 100644
> > > >>> --- a/arch/parisc/kernel/syscalls/syscall.tbl
> > > >>> +++ b/arch/parisc/kernel/syscalls/syscall.tbl
> > > >>> @@ -349,4 +349,5 @@
> > > >>>  347     common  preadv2                         sys_preadv2                     compat_sys_preadv2
> > > >>>  348     common  pwritev2                        sys_pwritev2                    compat_sys_pwritev2
> > > >>>  349     common  statx                           sys_statx
> > > >>> -350  common  io_pgetevents                   sys_io_pgetevents               compat_sys_io_pgetevents
> > > >>> \ No newline at end of file
> > > >>> +350  common  io_pgetevents                   sys_io_pgetevents               compat_sys_io_pgetevents
> > > >>> +351  common  rseq                            sys_rseq                        compat_sys_rseq
> > > >>
> > > >> You can't add the rseq syscall for parisc yet.
> > > >> It needs additional code in the kernel for parisc which hasn't been tested yet.
> > > >> See my initial untested patch at https://patchwork.kernel.org/patch/10495209/
> > > >
> > > > Thanks for your update!
> > > >
> > > > When I compiled the kernel I got below warnings.
> > > >
> > > > <stdin>:696:2: warning: #warning syscall nfsservctl not implemented [-Wcpp]
> > > > <stdin>:1335:2: warning: #warning syscall rseq not implemented [-Wcpp]
> > > >
> > > > I added an IGNORE entry nfsservctl in script/checksyscalls.sh because this
> > > > syscall is gone. But we definitely have to keep rseq entry on parisc
> > > > architecture.
> > >
> > > I prefer to keep the warning for rseq for now.
> >
> > I'm fine with this.
> >
> > > It reminds me that we still may want the rseq syscall.
> > > If the warning is a problem, you may simply add the __IGNORE_rseq define.
> >
> > But I still feel to keep an IGNORE entry, so once you test your patch; we can
> > remove IGNORE entry and update the syscall.tbl.
>
> If the warning is bogus (e.g. obsolete syscall), an IGNORE entry
> should be added.

nfsservctl  look like an obsolete one, so I added an IGNORE entry in
script/checksyscalls.h

> If the warning is due to a not-yet-implemented feature, IMHO it should not be
> silenced, as that would give the false impression that the feature is
> present and
> implemented.

Helge had done some implementation for rseq but not tested. So we
either add an IGNORE
entry or leave the warning as it is.

Thanks
Firoz

>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds