Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933200AbdC2Vgt (ORCPT ); Wed, 29 Mar 2017 17:36:49 -0400 Received: from mail-io0-f178.google.com ([209.85.223.178]:34740 "EHLO mail-io0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932914AbdC2Vf7 (ORCPT ); Wed, 29 Mar 2017 17:35:59 -0400 MIME-Version: 1.0 In-Reply-To: References: <20170329203908.GA39222@beast> From: Linus Torvalds Date: Wed, 29 Mar 2017 14:35:57 -0700 X-Google-Sender-Auth: xat_Mya9YwgV7bm4w30GmjrvdSc Message-ID: Subject: Re: [PATCH] x86/fpu: move FPU state into separate cache To: Kees Cook Cc: "H. Peter Anvin" , LKML , Rik van Riel , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , "x86@kernel.org" , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Peter Zijlstra , Dave Hansen , Yu-cheng Yu , Masahiro Yamada , Borislav Petkov , Christian Borntraeger , Thomas Garnier , Brian Gerst , He Chen , Mathias Krause , Fenghua Yu , Piotr Luc , Kyle Huey , Len Brown , KVM , "kernel-hardening@lists.openwall.com" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 787 Lines: 20 On Wed, Mar 29, 2017 at 2:30 PM, Linus Torvalds wrote: > > 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. Side note: that approach would seem to have the added advantage that because "fpu" now is an array, it syntactically acts like a pointer in C, so now syntactically it's going to be equivalent to having a "struct fpu *" pointer element, but from an allocation and code generation standpoint it all is like allocating the fpu structure together with the task struct. Linus