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

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Message-ID: <4DDC39F1.2060903@zytor.com>
Date:	Tue, 24 May 2011 16:06:25 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Dan Rosenberg <drosenberg@...curity.com>,
	Tony Luck <tony.luck@...il.com>, linux-kernel@...r.kernel.org,
	davej@...hat.com, kees.cook@...onical.com, davem@...emloft.net,
	eranian@...gle.com, torvalds@...ux-foundation.org,
	adobriyan@...il.com, penberg@...nel.org,
	Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Valdis.Kletnieks@...edu, pageexec@...email.hu
Subject: Re: [RFC][PATCH] Randomize kernel base address on boot

On 05/24/2011 02:16 PM, Ingo Molnar wrote:
> 
> On some systems holes can be pretty low as well - you'd have to research e820 
> maps submitted to lkml to see how common this is - but it's not terribly 
> common.
> 
> Some really old systems might have a hole between 15MB-16MB - but that's not an 
> issue if we load at 16 MB or higher.
> 

It definitely happens, and not just at 15-16 MiB either.

Doing this without actually consulting the memory map is dangerous as
hell; plus you have to verify that you're not clobbering anything else,
like the command line, initramfs or the linked list of data.

	-hpa
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