linux-kernel - Re: [PATCH 1/4] x86: add __X32_COND

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Message-Id: <027BAF5D-1473-4A35-8A58-D80315D52073@amacapital.net>
Date:   Sat, 19 Sep 2020 10:39:32 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     hpa@...or.com
Cc:     Andy Lutomirski <luto@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Eric Biederman <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, kexec@...ts.infradead.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Christoph Hellwig <hch@....de>, Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH 1/4] x86: add __X32_COND_SYSCALL() macro


> On Sep 19, 2020, at 10:14 AM, hpa@...or.com wrote:
> 
> On September 19, 2020 9:23:22 AM PDT, Andy Lutomirski <luto@...nel.org> wrote:
>>> On Fri, Sep 18, 2020 at 10:35 PM Christoph Hellwig <hch@...radead.org>
>>> wrote:
>>> 
>>> On Fri, Sep 18, 2020 at 03:24:36PM +0200, Arnd Bergmann wrote:
>>>> sys_move_pages() is an optional syscall, and once we remove
>>>> the compat version of it in favor of the native one with an
>>>> in_compat_syscall() check, the x32 syscall table refers to
>>>> a __x32_sys_move_pages symbol that may not exist when the
>>>> syscall is disabled.
>>>> 
>>>> Change the COND_SYSCALL() definition on x86 to also include
>>>> the redirection for x32.
>>>> 
>>>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>>> 
>>> Adding the x86 maintainers and Brian Gerst.  Brian proposed another
>>> problem to the mess that most of the compat syscall handlers used by
>>> x32 here:
>>> 
>>>   https://lkml.org/lkml/2020/6/16/664
>>> 
>>> hpa didn't particularly like it, but with your and my pending series
>>> we'll soon use more native than compat syscalls for x32, so something
>>> will need to change..
>> 
>> I'm fine with either solution.
> 
> My main objection was naming. x64 is a widely used synonym for x86-64, and so that is confusing.
> 
> 

The way I deal with the syscall wrappers is that I assume the naming makes no sense whatsoever, and I go from there. With this perspective, the patches are neither an improvement nor a worsening of the current situation.

(Similarly, the last column of the tables is useless garbage.  My last attempt to fix that stalled.)