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Message-ID: <CALCETrVudF5-buAHqGd3y1g8X3mnf6tmB5Av50k9WFL-yrbZmQ@mail.gmail.com>
Date: Wed, 29 Mar 2017 14:35:16 -0700
From: Andy Lutomirski <luto@...capital.net>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Kees Cook <keescook@...omium.org>, "H. Peter Anvin" <hpa@...or.com>,
LKML <linux-kernel@...r.kernel.org>, Rik van Riel <riel@...hat.com>,
Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
"x86@...nel.org" <x86@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Peter Zijlstra <peterz@...radead.org>, Dave Hansen <dave.hansen@...ux.intel.com>,
Yu-cheng Yu <yu-cheng.yu@...el.com>, Masahiro Yamada <yamada.masahiro@...ionext.com>,
Borislav Petkov <bp@...e.de>, Christian Borntraeger <borntraeger@...ibm.com>,
Thomas Garnier <thgarnie@...gle.com>, Brian Gerst <brgerst@...il.com>,
He Chen <he.chen@...ux.intel.com>, Mathias Krause <minipli@...glemail.com>,
Fenghua Yu <fenghua.yu@...el.com>, Piotr Luc <piotr.luc@...el.com>, Kyle Huey <me@...ehuey.com>,
Len Brown <len.brown@...el.com>, KVM <kvm@...r.kernel.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH] x86/fpu: move FPU state into separate cache
On Wed, Mar 29, 2017 at 2:30 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Wed, Mar 29, 2017 at 2:09 PM, Kees Cook <keescook@...omium.org> wrote:
>>
>> They're adjacent already, which poses a problem for the struct layout
>> randomization plugin, since adjacency may no longer be true (after
>> layout randomization). T
>
> What?
>
> The layout randomization can't change anything, if you just make the
> adjacency be done explicitly instead of by having the thing be a fixed
> member.
>
> The trivial model might be to just declare the fpu part as an unsized
> array at the end:
>
> /* Floating point and extended processor state */
> struct fpu fpu[];
>
> because there is no way in hell that any randomization code can move
> those kinds of unsized arrays around. If it does, the gcc plugin is
> such unbelievable garbage that it would be insane to depend on such
> shit in the first place.
>
Randomization also needs to leave thread_info at the beginning. Can it do that?
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