linux-kernel - Re: [PATCH 1/1] get_nr_restart_syscall() should return __NR_ia32_restart_syscall if __USER32

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Message-ID: <CALCETrXrTTrGU_ttG9m-SLkhHmrCs7O01-avEgOxadiGnCKiyA@mail.gmail.com>
Date:   Wed, 29 Mar 2017 09:59:36 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jan Kratochvil <jan.kratochvil@...hat.com>,
        Pedro Alves <palves@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] get_nr_restart_syscall() should return
 __NR_ia32_restart_syscall if __USER32_CS

On Wed, Mar 29, 2017 at 8:05 AM, Oleg Nesterov <oleg@...hat.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