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

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Message-ID: <20110529124702.GE26627@elte.hu>
Date:	Sun, 29 May 2011 14:47:02 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dan Rosenberg <drosenberg@...curity.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Tony Luck <tony.luck@...il.com>,
	linux-kernel@...r.kernel.org, davej@...hat.com,
	kees.cook@...onical.com, davem@...emloft.net, eranian@...gle.com,
	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


* H. Peter Anvin <hpa@...or.com> wrote:

> On 05/28/2011 05:18 AM, Ingo Molnar wrote:
> > 
> > Having half a megabyte of '__init buffer' at the beginning or end 
> > of the kernel image is no big deal, it's more than enough for 
> > good randomization and makes the whole thing image-loader 
> > invariant: we can freely shift the 'real' kernel image within 
> > this larger boundary without consulting RAM maps.
> 
> Sure, but you're also blowing any attempt at PMD alignment to 
> kingdom come.

Do you mean we'd not start at a 2MB boundary and thus would waste on 
average an about 0.125 worth of huge-TLB cache entry?

That does not look like a very big issue to me - but maybe i'm 
missing something and you mean something else.

Thanks,

	Ingo
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