linux-kernel - Re: [PATCH prototype] [0/8] Predictive bitmaps for ELF executables

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Date:	Mon, 24 Mar 2008 17:24:28 +0100
From:	Pavel Machek <pavel@....cz>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Nicholas Miell <nmiell@...cast.net>,
	Ulrich Drepper <drepper@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH prototype] [0/8] Predictive bitmaps for ELF executables

On Sun 2008-03-23 18:08:27, Andi Kleen wrote:
> > Is this good idea? Attacker can send you binary with the bitmap
> > inverted, it is now slow on your system and signature matches.
> 
> The first run will fix up any missing bits in the bitmap. Right 
> now it cannot get rid of unnecessary pages though unless you
> disable early_fault.
> 
> > ...might be important for benchmarks... 'here, see, Oracle is slow.
> > Feel free to verify the signature'.
> > 
> > ...ok, I guess it is not too serious, because it is similar to
> > fragmentation....
> 
> It is actually far better than fragmentation because the bitmap
> loader does IO always in big chunks -- not much seeking will go on. 
> The only problem is some wasted mmeory and more IO bandwidth
> usage (but typically binaries are not bigger than a few MB so 
> it's not too dramatic)
> 
> So in summary I don't think it's an issue.

Agreed.

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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