linux-kernel - Re: [PATCH] selftests/x86: Update map_shadow

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Message-ID: <339cd90a9b77706bd65b6d45f49edf009a9d46a0.camel@intel.com>
Date:   Fri, 1 Sep 2023 22:51:23 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "Lutomirski, Andy" <luto@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "Mehta, Sohil" <sohil.mehta@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "broonie@...nel.org" <broonie@...nel.org>
Subject: Re: [PATCH] selftests/x86: Update map_shadow_stack syscall nr

On Fri, 2023-09-01 at 15:19 -0700, Sohil Mehta wrote:
> My suggestion is originating from the belief that at somepoint the
> community decided that all *new* system call numbers would be the
> consistent across architectures (except alpha). So that would mean
> syscall number 453 has to be reserved on others even if it is an
> x86-only syscall.
> 
> If we don't do this, and let say a generic sys_foo comes along which
> uses the next available syscall number 453 on other archs, it would
> lead
> to an inconsistency because 453 it is already used up on x86.
> 
> My memory of this is a bit hazy from my implementation of User
> Interrupts more than a couple of years back. Also, I couldn't find
> any
> handy documentation to support my belief. I'll try to dig more.

Putting reservations in sounds like a good idea in any case. I take it
you would like to send the patch? Otherwise let me know.