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Date: Thu, 5 Jan 2017 11:00:20 -0800
From: Thomas Garnier <thgarnie@...gle.com>
To: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Ingo Molnar <mingo@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	"H . Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>, Borislav Petkov <bp@...en8.de>, 
	Andy Lutomirski <luto@...nel.org>, Dave Hansen <dave@...1.net>, Chen Yucong <slaoub@...il.com>, 
	Paul Gortmaker <paul.gortmaker@...driver.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Masahiro Yamada <yamada.masahiro@...ionext.com>, 
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Anna-Maria Gleixner <anna-maria@...utronix.de>, 
	Boris Ostrovsky <boris.ostrovsky@...cle.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, 
	Michael Ellerman <mpe@...erman.id.au>, Juergen Gross <jgross@...e.com>, 
	Richard Weinberger <richard@....at>, "the arch/x86 maintainers" <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Kernel Hardening <kernel-hardening@...ts.openwall.com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC] x86/mm/KASLR: Remap GDTs at fixed location

On Thu, Jan 5, 2017 at 10:56 AM, Arjan van de Ven <arjan@...ux.intel.com> wrote:
> On 1/5/2017 8:40 AM, Thomas Garnier wrote:
>>
>> Well, it happens only when KASLR memory randomization is enabled. Do
>> you think it should have a separate config option?
>
>
> no I would want it a runtime option.... "sgdt from ring 3" is going away
> with UMIP (and is already possibly gone in virtual machines, see
> https://lwn.net/Articles/694385/) and for those cases it would be a shame
> to lose the randomization
>

That's correct. When UMIP is enabled, we should disable fixed location
for both GDT and IDT. Glad to do that when UMIP support is added.

-- 
Thomas

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