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From: Andy Lutomirski <luto@amacapital.net>
Date: Wed, 29 Mar 2017 09:59:36 -0700
Message-ID: <CALCETrXrTTrGU_ttG9m-SLkhHmrCs7O01-avEgOxadiGnCKiyA@mail.gmail.com>
Subject: Re: [PATCH 1/1] get_nr_restart_syscall() should return
 __NR_ia32_restart_syscall if __USER32_CS
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Denys Vlasenko <dvlasenk@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        Ingo Molnar <mingo@redhat.com>,
        Jan Kratochvil <jan.kratochvil@redhat.com>,
        Pedro Alves <palves@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        X86 ML <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Wed, Mar 29, 2017 at 8:05 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> On 03/28, Oleg Nesterov wrote:
>>
>> On 03/28, Andy Lutomirski wrote:
>> >
>> > How about we store the syscall arch to be restored in task_struct
>> > along with restart_block?
>>
>> Yes, perhaps we will have to finally do this. Not really nice too.
>
> OK, how about the hack below?
>
> I do not want to a new member into task_struct/restart_block, so the
> patch below adds a sticky TS_COMPAT bit which logically is a member
> of "struct restart_block".

Okay, but I'd much rather we just added a helper that's called in the
few places that actually write to restart_block.

Or we just add the new syscall nr and see what breaks.  The answer
could well be nothing at all.

--Andy