linux-kernel - Re: [patch] x86_64: fix is_at

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Message-Id: <200607311054.38585.ak@suse.de>
Date:	Mon, 31 Jul 2006 10:54:38 +0200
From:	Andi Kleen <ak@...e.de>
To:	Chuck Ebbert <76306.1226@...puserve.com>
Cc:	Albert Cahalan <acahalan@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch] x86_64: fix is_at_popf() for compat tasks

On Monday 31 July 2006 09:22, Chuck Ebbert wrote:
> When testing for the REX instruction prefix, first check
> for a 32-bit task because in compat mode the REX prefix is an
> increment instruction.

is_compat_task doesn't actually say that a task is in compat mode
(it refers to the Linux compat layer, not x86-64 compat mode)

A better test would be regs->cs == __USER32_CS, but in theory
there could be other code segments in LDT. I guess that can 
be ignored though.

-Andi
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