From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yu-cheng Yu Subject: Re: [PATCH v10 01/26] Documentation/x86: Add CET description Date: Tue, 12 May 2020 16:20:32 -0700 Message-ID: <5cc163ff9058d1b27778e5f0a016c88a3b1a1598.camel@intel.com> References: <20200429220732.31602-1-yu-cheng.yu@intel.com> <20200429220732.31602-2-yu-cheng.yu@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Dave Hansen , 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 , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz List-Id: linux-arch.vger.kernel.org On Wed, 2020-04-29 at 16:02 -0700, Yu-cheng Yu wrote: > On Wed, 2020-04-29 at 15:53 -0700, Dave Hansen wrote: > > On 4/29/20 3:07 PM, Yu-cheng Yu wrote: > > > +Note: > > > + There is no CET-enabling arch_prctl function. By design, CET is enabled > > > + automatically if the binary and the system can support it. > > > > I think Andy and I danced around this last time. Let me try to say it > > more explicitly. > > > > I want CET kernel enabling to able to be disconnected from the on-disk > > binary. I want a binary compiled with CET to be able to disable it, and > > I want a binary not compiled with CET to be able to enable it. I want > > different threads in a process to be able to each have different CET status. > > The kernel patches we have now can be modified to support this model. If after > discussion this is favorable, I will modify code accordingly. To turn on/off and to lock CET are application-level decisions. The kernel does not prevent any of those. Should there be a need to provide an arch_prctl() to turn on CET, it can be added without any conflict to this series. > > Which JITs was this tested with? I think as a bare minimum we need to > > know that this design can accommodate _a_ modern JIT. It would be > > horrible if the browser javascript engines couldn't use this design, for > > instance. > > JIT work is still in progress. When that is available I will test it. I found CET has been enabled in LLVM JIT, Mesa JIT as well as sljit which is used by jit. So the current model works with JIT. Yu-cheng From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga04.intel.com ([192.55.52.120]:19892 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726031AbgELXU3 (ORCPT ); Tue, 12 May 2020 19:20:29 -0400 Message-ID: <5cc163ff9058d1b27778e5f0a016c88a3b1a1598.camel@intel.com> Subject: Re: [PATCH v10 01/26] Documentation/x86: Add CET description From: Yu-cheng Yu Date: Tue, 12 May 2020 16:20:32 -0700 In-Reply-To: References: <20200429220732.31602-1-yu-cheng.yu@intel.com> <20200429220732.31602-2-yu-cheng.yu@intel.com> Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Dave Hansen , 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 , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang Message-ID: <20200512232032.6Uc0btw4AOETeQYiBm-ksI-ZUs0adBUrTupsvMPB-is@z> On Wed, 2020-04-29 at 16:02 -0700, Yu-cheng Yu wrote: > On Wed, 2020-04-29 at 15:53 -0700, Dave Hansen wrote: > > On 4/29/20 3:07 PM, Yu-cheng Yu wrote: > > > +Note: > > > + There is no CET-enabling arch_prctl function. By design, CET is enabled > > > + automatically if the binary and the system can support it. > > > > I think Andy and I danced around this last time. Let me try to say it > > more explicitly. > > > > I want CET kernel enabling to able to be disconnected from the on-disk > > binary. I want a binary compiled with CET to be able to disable it, and > > I want a binary not compiled with CET to be able to enable it. I want > > different threads in a process to be able to each have different CET status. > > The kernel patches we have now can be modified to support this model. If after > discussion this is favorable, I will modify code accordingly. To turn on/off and to lock CET are application-level decisions. The kernel does not prevent any of those. Should there be a need to provide an arch_prctl() to turn on CET, it can be added without any conflict to this series. > > Which JITs was this tested with? I think as a bare minimum we need to > > know that this design can accommodate _a_ modern JIT. It would be > > horrible if the browser javascript engines couldn't use this design, for > > instance. > > JIT work is still in progress. When that is available I will test it. I found CET has been enabled in LLVM JIT, Mesa JIT as well as sljit which is used by jit. So the current model works with JIT. Yu-cheng