linux-kernel - Re: [PATCH V5] x86: NX protection for kernel data

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Date:	Tue, 13 Oct 2009 08:03:12 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	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>, Rusty Russell <rusty@...tcorp.com.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Howells <dhowells@...hat.com>,
	Aristeu Rozanski <aris@...hat.com>
Subject: Re: [PATCH V5] x86: NX protection for kernel data


* Arjan van de Ven <arjan@...radead.org> wrote:

> On Mon, 12 Oct 2009 21:03:17 -0400
> Siarhei Liakh <sliakh.lkml@...il.com> wrote:
> 
> > This patch expands functionality of CONFIG_DEBUG_RODATA to set main
> > (static) kernel data area as NX.
> > The following steps are taken to achieve this:
> > 1. Linker script is adjusted so .text always starts and ends on a
> > page boundary 2. Linker script is adjusted so .rodata and .data
> > always start and end on a page boundary
> > 3. void mark_nxdata_nx(void) added to arch/x86/mm/init.c with actual
> > functionality: NX is set for all pages from _etext through _end.
> > 4. mark_nxdata_nx() called from free_initmem() (after init has been
> > released) 5. free_init_pages() sets released memory NX in
> > arch/x86/mm/init.c
> > 
> > The patch have been developed for Linux 2.6.31-rc7 x86 by Siarhei
> > Liakh <sliakh.lkml@...il.com> and Xuxian Jiang <jiang@...ncsu.edu>.
> > 
> 
> I like doing this, but... maybe it is useful to have a diff of the 
> pagetable dump (PT_DUMP config option) to show the effect, in the 
> changelog. That'd be like the proof on the pudding...

That's a good suggestion. Siarhei Liakh, mind doing that?

Thanks,

	Ingo
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