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From: Ingo Molnar <mingo@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 1/4] x86/syscall: sign-extend system calls on entry to int
Date: Sun, 16 May 2021 09:48:19 +0200	[thread overview]
Message-ID: <YKDOQxRS+kX1WhQq@gmail.com> (raw)
In-Reply-To: <20210515011015.2707542-2-hpa@zytor.com>


* H. Peter Anvin <hpa@zytor.com> wrote:

> This is an ABI change, but is in fact a revert to the original x86-64
> ABI. The original assembly entry code would zero-extend the system
> call number; this patch uses sign extend to be explicit that this is
> treated as a signed number (although in practice it makes no
> difference, of course) and to avoid people getting the idea of
> "optimizing" it, as has happened on at least two(!) separate
> occasions.

The original x86-64 ABI as documented by AMD, as we (probably) never had 
this in Linux, right?

Sounds sensible to do this, assuming nothing relies on the weirdness.

Thanks,

	Ingo

  reply	other threads:[~2021-05-16  7:48 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-15  1:10 [RFC v3 PATCH 0/4] x86/syscall: use int for x86-64 system calls H. Peter Anvin
2021-05-15  1:10 ` [PATCH v3 1/4] x86/syscall: sign-extend system calls on entry to int H. Peter Anvin
2021-05-16  7:48   ` Ingo Molnar [this message]
2021-05-17 20:23     ` H. Peter Anvin
2021-05-15  1:10 ` [PATCH v3 2/4] x86/syscall: update and extend selftest syscall_numbering_64 H. Peter Anvin
2021-05-16  7:52   ` Ingo Molnar
2021-05-18  0:26     ` H. Peter Anvin
2021-05-18 15:04     ` H. Peter Anvin
2021-05-15  1:10 ` [PATCH v3 3/4] x86/syscall: treat out of range and gap system calls the same H. Peter Anvin
2021-05-15  1:10 ` [PATCH v3 4/4] x86/syscall: use int everywhere for system call numbers H. Peter Anvin
2021-05-15 15:37   ` Andy Lutomirski
2021-05-15 17:41     ` H. Peter Anvin
2021-05-15 17:42     ` H. Peter Anvin
     [not found]       ` <2ebf1bac-93c1-4b7f-add4-4ede3c149b52@www.fastmail.com>
2021-05-15 21:07         ` H. Peter Anvin

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