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: <b0ca952a-fd82-7833-ac82-ea8ecad48b53@zytor.com>
Date:   Wed, 12 May 2021 15:09:08 -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

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.

	-hpa