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

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Message-ID: <817ecb6f0907191802g4fd0970dj9e8327d44cf7e5a@mail.gmail.com>
Date:	Sun, 19 Jul 2009 21:02:47 -0400
From:	Siarhei Liakh <sliakh.lkml@...il.com>
To:	"H. Peter Anvin" <hpa@...or.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

For now I have only tested it on my home system and qemu. Actuallym in
both cases, I had to compile kernel with only CONFIG_PCI_GOBIOS=y,
since Kernel prefers other ways to access PCI when possible (with
CONFIG_PCI_GOANY=y).

On Sun, Jul 19, 2009 at 8:53 PM, H. Peter Anvin<hpa@...or.com> wrote:
> 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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