linux-kernel - Re: [RFC][PATCH] Randomize kernel base address on boot

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Message-ID: <4DE5360D.5070809@zytor.com>
Date:	Tue, 31 May 2011 11:40:13 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Matthew Garrett <mjg@...hat.com>
CC:	Dan Rosenberg <drosenberg@...curity.com>,
	Tony Luck <tony.luck@...il.com>, linux-kernel@...r.kernel.org,
	kees.cook@...onical.com, davej@...hat.com,
	torvalds@...ux-foundation.org, adobriyan@...il.com,
	eranian@...gle.com, penberg@...nel.org, davem@...emloft.net,
	Arjan van de Ven <arjan@...radead.org>,
	Valdis.Kletnieks@...edu, Andrew Morton <akpm@...ux-foundation.org>,
	pageexec@...email.hu, Ingo Molnar <mingo@...e.hu>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [RFC][PATCH] Randomize kernel base address on boot

On 05/31/2011 09:52 AM, Matthew Garrett wrote:
> On Thu, May 26, 2011 at 04:39:27PM -0400, Dan Rosenberg wrote:
> 
>> 1. I'm nearly finished a first draft of code to parse the BIOS E820
>> memory map to determine where it's safe to place the randomized kernel.
>> This code accounts for overlapping regions, as well as potential
>> conflicts in region types (free vs. reserved, etc.), in favor of
>> non-free types.  The end result is, I'll have a reasonable upper bound.
> 
> The BIOS E820 map, or the kernel representation? In either case, this 
> isn't going to work well with EFI. There are regions that will be marked 
> as available in the E820 map that we *mustn't* touch until we've entered 
> EFI virtual mode.
> 
> (This is, clearly, insane).
> 

I believe we could (should!) mark them reserved, not available, in the
E820 map and free them later.

	-hpa
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