linux-kernel - Re: [PATCH 0/5 v2] [GIT PULL] x86/jump label: Paranoid checks and 2 or 5 byte nops

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Date:	Thu, 02 Feb 2012 14:07:11 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jason Baron <jbaron@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 0/5 v2] [GIT PULL] x86/jump label: Paranoid checks and
 2 or 5 byte nops

On 02/02/2012 02:04 PM, Steven Rostedt wrote:
> commit 7bbd9688727dd30cd44b90b3c9c35f0f66af77ff
> Author: Steven Rostedt<srostedt@...hat.com>
> Date:   Thu Feb 2 16:55:43 2012 -0500
>
>      x86/jump labels: Handle initialization of enabled nops
>
>      When jump labels are initialized at boot up, they are compared
>      to the default_nop before switching to the ideal nop.
>
>      But if a jump label is enabled by default on start up, the
>      enabled code does not test against the default nop, only the
>      ideal nop. But as this jump label has not been converted to the
>      ideal nop, it fails the check, and will crash the box.
>
>      The enabled path needs to be aware of initialization too.
>
>      Reported-by: Ingo Molnar<mingo@...e.hu>
>      Signed-off-by: Steven Rostedt<rostedt@...dmis.org>
>

Would it make more sense to keep track of three states:

"Default"
"Enabled"
"Disabled"

	-?
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