linux-kernel - Re: [PATCH RFC] x86: remove toolchain check for X32 ABI capability

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Message-ID: <1992c9cf-739e-d98f-85c0-bbcf7df123ea@kernel.org>
Date:   Tue, 8 Jun 2021 10:26:30 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Fangrui Song <maskray@...gle.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "H . J . Lu" <hjl.tools@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Brian Gerst <brgerst@...il.com>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Chao Yu <chao@...nel.org>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        Ingo Molnar <mingo@...hat.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jethro Beekman <jethro@...tanix.com>,
        Kees Cook <keescook@...omium.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Sasha Levin <sashal@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Takashi Iwai <tiwai@...e.com>,
        ALSA Development Mailing List <alsa-devel@...a-project.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>
Subject: Re: [PATCH RFC] x86: remove toolchain check for X32 ABI capability

Hi Masahiro,

On 6/7/2021 12:39 AM, Masahiro Yamada wrote:
> On Sun, Feb 28, 2021 at 3:49 PM Nathan Chancellor <nathan@...nel.org> wrote:
>>
>> On Sun, Feb 28, 2021 at 12:15:16PM +0900, Masahiro Yamada wrote:
>>> On Sun, Feb 28, 2021 at 3:41 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>>>>
>>>> This commit reverts 0bf6276392e9 ("x32: Warn and disable rather than
>>>> error if binutils too old").
>>>>
>>>> The help text in arch/x86/Kconfig says enabling the X32 ABI support
>>>> needs binutils 2.22 or later. This is met because the minimal binutils
>>>> version is 2.23 according to Documentation/process/changes.rst.
>>>>
>>>> I would not say I am not familiar with toolchain configuration, but
>>>
>>> I mean:
>>> I would not say I am familiar ...
>>> That is why I added RFC.
>>>
>>> I appreciate comments from people who are familiar
>>> with toolchains (binutils, llvm).
>>>
>>> If this change is not safe,
>>> we can move this check to Kconfig at least.
>>
>> Hi Masahiro,
>>
>> As Fangrui pointed out, there are two outstanding issues with x32 with
>> LLVM=1, both seemingly related to LLVM=1.
> 
> Is this still a problem for Clang built Linux?
> 
> 
> 
>> https://github.com/ClangBuiltLinux/linux/issues/514
> 
> I am not tracking the status.
> What was the conclusion?

This appears to no longer be reproducible so I closed it.

>> https://github.com/ClangBuiltLinux/linux/issues/1141
> 
> 
> This got marked "unreproducible"

I just had a look at this and it is still reproducible (see the bug for 
details).

>> Additionally, there appears to be one from Arnd as well but that one has
>> received no triage yet.
>>
>> https://github.com/ClangBuiltLinux/linux/issues/1205
> 
> Same as well.

Yeah, I cannot reproduce this.

It seems like a Kconfig test would still be best for the issue above, if 
it is not too much to maintain.

Cheers,
Nathan