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

From: H. Peter Anvin
Date: Sun Jul 19 2009 - 20:59:20 EST


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@xxxxxxxxx> and Xuxian Jiang <jiang@xxxxxxxxxxx>.
>

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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