linux-kernel - Re: [RFC v2 PATCH 7/7] x86/entry: use int for syscall number; handle all invalid syscall nrs

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Message-ID: <C2397A4D-8709-43F9-9967-51538B2B87FE@zytor.com>
Date:   Wed, 12 May 2021 15:24:50 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2 PATCH 7/7] x86/entry: use int for syscall number; handle all invalid syscall nrs

Yes, indeed. I hope my reply to Ingo clarifies it as I'm going to try to wordsmith that into a better piece of text.

On May 12, 2021 3:22:05 PM PDT, Thomas Gleixner <tglx@...utronix.de> wrote:
>On Wed, May 12 2021 at 15:09, H. Peter Anvin wrote:
>> On 5/12/21 11:34 AM, Thomas Gleixner wrote:
>>>>
>>>> That is intentional, as (again) system calls are int.
>>> 
>>> They are 'int' kernel internally, but _NOT_ at the user space
>visible
>>> side. Again: man syscall
>>> 
>>>      syscall(long number,...);
>>> 
>>> So that results in a user ABI change.
>>> 
>>>> As stated in my reply to Ingo, I'll clean the various descriptions
>and
>>>> try to capture the discussion better.
>>> 
>>> If we agree to go there then this wants to be a seperate commit
>which
>>> does nothing else than changing this behaviour.
>>> 
>>
>> Good idea.
>>
>> As far as this being a user ABI change, this is actually a revert to
>the 
>> original x86-64 ABI; see my message to Ingo.
>
>I'm not against that change, but it has to be well justified and the
>reasoning wants to be in the changelog. You know the drill :)
>
>Thanks,
>
>        tglx

-- 
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