linux-kernel - Re: i686 quirk for AMD Geode

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Message-ID: <a91053ef0911111823v52669d18p7e5812076a63f03e@mail.gmail.com>
Date:	Wed, 11 Nov 2009 18:23:14 -0800
From:	Matt Thrailkill <matt.thrailkill@...il.com>
To:	Willy Tarreau <w@....eu>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Pavel Machek <pavel@....cz>, Avi Kivity <avi@...hat.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Matteo Croce <technoboy85@...il.com>,
	Sven-Haegar Koch <haegar@...net.de>,
	linux-kernel@...r.kernel.org
Subject: Re: i686 quirk for AMD Geode

On Wed, Nov 11, 2009 at 1:32 AM, Willy Tarreau <w@....eu> wrote:
> All I can say is that executing a NOP results in no state change in
> the processor except the instruction pointer which points to the
> next instruction after execution. Since a NOP changes nothing, it
> cannot be used alone to provide any privilege, access to data or
> any such thing. Since it does not perform any jump, it cannot either
> be used to take back control of the execution flow. And it is certain
> that the next instruction after it will be executed, so if the NOP
> crosses a page boundary and completes on a non-executable one, the
> next instruction will trigger the PF.
>
> So I can't see how a NOP can be used to circumvent any protection.

So a nop(l) sled won't be a problem, right?
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