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

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Date:   Thu, 13 May 2021 17:38:02 -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 3:22 PM, Thomas Gleixner wrote:
>>
>> 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 :)
> 

FYI:

So in the process of breaking up and better document this patch, I have 
looked at the syscall_numbering_64 (and have rewritten it to be more 
complete.)

I found that running it under strace fails, as strace (possibly ptrace, 
possibly the strace binary) causes %rax = 2^32 to be clobbered to zero 
already...

More motivation, I guess.

	-hpa