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: <87mtsz619u.ffs@nanos.tec.linutronix.de>
Date:   Thu, 13 May 2021 00:22:05 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "H. Peter Anvin" <hpa@...or.com>, 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

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