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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