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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>, Jonathan Corbet <corbet@lwn.net>,
	Thomas Gleixner <tglx@kernel.org>
Subject: Re: [PATCH] x86: Start removing X86_X32_ABI
Message-ID: <20260526204306.0YTo1ClU@linutronix.de>
References: <20260523093734.A3AR7reJ@linutronix.de>
 <10BF3F18-4709-43D6-979C-49067707F1C1@zytor.com>
 <20260526104051.MmQQ03a8@linutronix.de>
 <5FC3AA08-47C8-46CE-9758-20ECDE6CE018@zytor.com>
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In-Reply-To: <5FC3AA08-47C8-46CE-9758-20ECDE6CE018@zytor.com>

On 2026-05-26 08:54:56 [-0700], H. Peter Anvin wrote:
> No, because you don't want the same system call number to have
> different meaning on different kernels, potentially succeed with
> totally the wrong meaning.

My point is that if you rip out x32 entirely there is no point in
reversing the syscall numbers since you can't use x32 anyway.

> System call numbers or even mechanisms are in no wise tied to the ELF
> type. An x86-64 binary can issue x86-64, x32 or i386 system calls,
> even from 64-bit mode!

Hmm. Judging from compat_elf_check_arch() it looks like it is
restricted. 

But *why* have syscalls if nothing else works? It is not that you have a
natural environment where these things work and in a later kernel they
behave differently. It just not working.

Sebastian