linux-kernel - Re: [PATCH 2/6] arch: x86: Wrap TIF

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Message-ID: <874kpqjin3.fsf@collabora.com>
Date:   Wed, 29 Jul 2020 14:11:44 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Christoph Hellwig <hch@....de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...omium.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel@...labora.com
Subject: Re: [PATCH 2/6] arch: x86: Wrap TIF_IA32 checks

Andy Lutomirski <luto@...nel.org> writes:

> On Tue, Jul 28, 2020 at 9:46 PM Gabriel Krisman Bertazi
> <krisman@...labora.com> wrote:
>>
>> Andy Lutomirski <luto@...nel.org> writes:
>>
>> > On Tue, Jul 28, 2020 at 1:22 PM Gabriel Krisman Bertazi
>> > <krisman@...labora.com> wrote:
>> >>
>> >> In preparation to remove TIF_IA32, add wrapper that check the process
>> >> has IA32 ABI without using the flag directly.
>> >
>> > Thank you for doing this, but let's please do it right.  There is,
>> > fundamentally, no such thing as a "process with IA32 ABI".
>>
>> Hi Andy,
>>
>> Thanks a lot for your review.
>>
>> As you can see, I'm learning my way here. Can you clarify "there is no
>> such a thing as a 'process with IA32 ABI'"?  I'm not sure if I confused
>> the terminology or if (more worrisome for me) I got the concepts wrong.
>>
>> My understanding is that TIF_IA32 marks a thread that is running under
>> the 32-bit compat mode, which would be running a 32-bit process (as in
>> compiled with -m32, for instance), while TIF_X32 marks a process running
>> under the X32 ABI.  Each process would have only one of these
>> "personalities". This is what I meant by a process with IA32 ABI (which
>> is wrong in any case).  Is there more to it, or is the problem the
>> terminology I used?
>
> There's more to it.

Thanks again for the explanation!

>> I don't have any comments on the other things you mentioned, except that
>> I need to go through them and better understand your suggestions.  Would
>> you prefer me to rework this patch series with what you suggested or is
>> this something you want to take over and do yourself?  Both ways are
>> fine by me.
>
> Please rework it :)  I have seriously limited bandwidth right now.

Will do.

-- 
Gabriel Krisman Bertazi