linux-kernel - Re: [PATCH v5] RO/NX protection for loadable kernel modules

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Message-ID: <87skh29ru2.fsf@basil.nowhere.org>
Date:	Sun, 12 Jul 2009 11:24:37 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Siarhei Liakh <sliakh.lkml@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@....de>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-cris-kernel@...s.com
Subject: Re: [PATCH v5] RO/NX protection for loadable kernel modules

Rusty Russell <rusty@...tcorp.com.au> writes:
>
> (I like the idea of trying kmalloc and falling back, simply because it reduces 
> TLB pressure,

I implemented this for 32bit in 2.4, but I always had second thoughts
if that was really reducing TLB pressure.

x86 CPUs have separated TLBs for 2MB and 4K and they all have much
more 4K entries. So it might actually be worse to use the 2MB TLBs for
this.

> but that's probably best done after unification).

Trying kmalloc doesn't work on x86-64

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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