linux-kernel - Re: [PATCH] x86: Reducing footprint of BIOS32 service mappings

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Message-ID: <4A63C00A.2070805@zytor.com>
Date:	Sun, 19 Jul 2009 17:53:30 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Siarhei Liakh <sliakh.lkml@...il.com>
CC:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Ingo Molnar <mingo@...e.hu>, James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@....de>, Thomas Gleixner <tglx@...utronix.de>,
	linux-cris-kernel@...s.com, Roland Dreier <rdreier@...co.com>
Subject: Re: [PATCH] x86: Reducing footprint of BIOS32 service mappings

Siarhei Liakh wrote:
> According to BIOS32 specification
> (http://members.datafast.net.au/dft0802/specs/bios32.pdf), at most two
> pages per BIOS32 service should be set executable and no pages need to
> be writeable. This patch modifies bios32_service() to set proper page
> access permissions at time of service discovery, as described in the
> specification.
> Further, hardcoded protection of memory area between 640k to 1Mb have
> been removed from static_protections(), since only pages mentioned
> above need to be executable, not whole BIOS region.
> 
> The patch have been developed for Linux 2.6.30 x86 by Siarhei Liakh
> <sliakh.lkml@...il.com> and Xuxian Jiang <jiang@...ncsu.edu>.
> 

Specifications mean little in the BIOS space, unfortunately.  Do we have
any notion about how many machines this has been tested on?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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