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: <486B4C98-FFD1-40B9-B7AF-5323DE07A0FE@zytor.com>
Date:   Thu, 13 May 2021 20:23:17 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Andy Lutomirski <andy@...ux.luto.us>,
        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

Yeah. Also, x32 long is 32 bits...

On May 13, 2021 8:18:37 PM PDT, Andy Lutomirski <andy@...ux.luto.us> wrote:
>On 5/13/21 5:38 PM, H. Peter Anvin wrote:
>> 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.
>> 
>
>Indeed.
>
>I would love to go back in time and switch to long, but there are
>plenty
>of things that use int now.  I suppose we could try to make it long for
>real, but seccomp has u32 baked into its ABI.

-- 
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