Date: Sun, 12 Jul 2009 08:32:27 -0700
From: Arjan van de Ven <arjan@infradead.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>, Siarhei Liakh <sliakh.lkml@gmail.com>,
       linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org,
       James Morris <jmorris@namei.org>,
       Andrew Morton <akpm@linux-foundation.org>, Andi Kleen <ak@muc.de>,
       Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
       linux-cris-kernel@axis.com
Subject: Re: [PATCH v5] RO/NX protection for loadable kernel modules
Message-ID: <20090712083227.39939849@infradead.org>
In-Reply-To: <200907121928.28887.rusty@rustcorp.com.au>
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	<200907121410.39874.rusty@rustcorp.com.au>
	<20090712004524.2f0c4e57@infradead.org>
	<200907121928.28887.rusty@rustcorp.com.au>
Organization: Intel
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On Sun, 12 Jul 2009 19:28:27 +0930
Rusty Russell <rusty@rustcorp.com.au> wrote:

> On Sun, 12 Jul 2009 05:15:24 pm Arjan van de Ven wrote:
> > Rusty Russell <rusty@rustcorp.com.au> wrote:
> > > (I like the idea of trying kmalloc and falling back, simply
> > > because it reduces TLB pressure, but that's probably best done
> > > after unification).
> >
> > or using a non-power-of-two get_free_pages() thing...
> >
> > some architectures will need to know that memory needs to be
> > executable at allocation time so that it can be put in an
> > executable address range etc...
> 
> Yes, maybe that's better than kmalloc.  On my laptop I have 105
> modules loaded, with 3778464 total length: I'm wasting 206944 bytes
> on unused tails of pages.  But that's only 0.06% of my memory.
>

105 is also a sign that you picked a somewhat suboptimal config...
that's of course your choice but it's a choice that has a small price,
if you don't want to pay that price, changing the config to not be
entirely insane is a good answer as well ;-)


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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