linux-kernel - Re: Reading /dev/mem by dd

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Date:	Fri, 13 Nov 2009 00:29:35 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Krzysztof Halasa <khc@...waw.pl>
Cc:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Andi Kleen <andi@...stfloor.org>,
	Robert Hancock <hancockrwd@...il.com>,
	"Anton D. Kachalov" <mouse@...c.ru>, linux-kernel@...r.kernel.org
Subject: Re: Reading /dev/mem by dd

On Thu, Nov 12, 2009 at 10:07:22PM +0100, Krzysztof Halasa wrote:
> "Henrique de Moraes Holschuh" <hmh@....eng.br> writes:
> 
> > In this case, the problem seems to be access over /dev/mem to stuff the
> > kernel is already taking care of.
> 
> Not sure if local APIC counts as "PCI space and the BIOS code and data
> regions" but:
> 
> $ grep STRICT_DEVMEM -A 15 arch/x86/Kconfig.debug
> config STRICT_DEVMEM
>         bool "Filter access to /dev/mem"
>         ---help---
> 

Yes, having this option turned on an access to LAPIC/IO_APIC
space will be forbidden.

	-- Cyrill
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