From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: Re: [RFC PATCH v2 16/27] mm: Modify can_follow_write_pte/pmd for shadow stack Date: Tue, 17 Jul 2018 16:15:10 -0700 Message-ID: References: <20180710222639.8241-1-yu-cheng.yu@intel.com> <20180710222639.8241-17-yu-cheng.yu@intel.com> <1531328731.15351.3.camel@intel.com> <45a85b01-e005-8cb6-af96-b23ce9b5fca7@linux.intel.com> <1531868610.3541.21.camel@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1531868610.3541.21.camel@intel.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Yu-cheng Yu , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra List-Id: linux-arch.vger.kernel.org On 07/17/2018 04:03 PM, Yu-cheng Yu wrote: > We need to find a way to differentiate "someone can write to this PTE" > from "the write bit is set in this PTE". Please think about this: Should pte_write() tell us whether PTE.W=1, or should it tell us that *something* can write to the PTE, which would include PTE.W=0/D=1? From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com ([134.134.136.20]:40998 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730092AbeGQXuF (ORCPT ); Tue, 17 Jul 2018 19:50:05 -0400 Subject: Re: [RFC PATCH v2 16/27] mm: Modify can_follow_write_pte/pmd for shadow stack References: <20180710222639.8241-1-yu-cheng.yu@intel.com> <20180710222639.8241-17-yu-cheng.yu@intel.com> <1531328731.15351.3.camel@intel.com> <45a85b01-e005-8cb6-af96-b23ce9b5fca7@linux.intel.com> <1531868610.3541.21.camel@intel.com> From: Dave Hansen Message-ID: Date: Tue, 17 Jul 2018 16:15:10 -0700 MIME-Version: 1.0 In-Reply-To: <1531868610.3541.21.camel@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Yu-cheng Yu , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , "Ravi V. Shankar" , Vedvyas Shanbhogue Message-ID: <20180717231510.bi36sXQNDwLGo8V-7Y1MUYULATj7_9NgZt81xLIAsBg@z> On 07/17/2018 04:03 PM, Yu-cheng Yu wrote: > We need to find a way to differentiate "someone can write to this PTE" > from "the write bit is set in this PTE". Please think about this: Should pte_write() tell us whether PTE.W=1, or should it tell us that *something* can write to the PTE, which would include PTE.W=0/D=1?