linux-kernel - Re: [PATCH] x86 : Add NX protection for kernel data on 64 bit

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Message-ID: <4D7E9F0C.2010504@zytor.com>
Date:	Mon, 14 Mar 2011 16:04:44 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	matthieu castet <castet.matthieu@...e.fr>
CC:	lkml <linux-kernel@...r.kernel.org>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Lin Ming <ming.m.lin@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] x86 : Add NX protection for kernel data on 64 bit

On 03/13/2011 11:37 AM, matthieu castet wrote:
> Cpu hotplug code read data in head_64.S (phys_base) before enabling NX, so when
> we enable NX on data, an triple fault happen because a reserved bit is set.
> It was fixed by allocating dedicated page table for ident mapping in trampoline.
> Now data can be protected by NX.
> 
> The Low kernel Mapping is also set to NX.
> 
> Finaly we preserve large page mapping by applying nx in free_init_pages only 
> when we switch to NX mode

The right way to do this is to have initial_page_table and keep it
around, just as we already do on 32 bits... yet another thing that can
be merged instead of coming up with a separate solution.

	-hpa
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