From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH 00/22] add support for Clang LTO Date: Mon, 6 Jul 2020 11:39:33 -0700 Message-ID: <20200706183933.GE9247@paulmck-ThinkPad-P72> References: <20200701114027.GO4800@hirez.programming.kicks-ass.net> <20200701140654.GL9247@paulmck-ThinkPad-P72> <20200701150512.GH4817@hirez.programming.kicks-ass.net> <20200701160338.GN9247@paulmck-ThinkPad-P72> <20200702082040.GB4781@hirez.programming.kicks-ass.net> <20200702175948.GV9247@paulmck-ThinkPad-P72> <20200703131330.GX4800@hirez.programming.kicks-ass.net> <20200703144228.GF9247@paulmck-ThinkPad-P72> <20200706162633.GA13288@paulmck-ThinkPad-P72> <20200706182926.GH4800@hirez.programming.kicks-ass.net> Reply-To: paulmck@kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200706182926.GH4800@hirez.programming.kicks-ass.net> Sender: linux-kbuild-owner@vger.kernel.org To: Peter Zijlstra Cc: Marco Elver , Nick Desaulniers , Sami Tolvanen , Masahiro Yamada , Will Deacon , Greg Kroah-Hartman , Kees Cook , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , Linux Kbuild mailing list , LKML , linux-pci@vger.kernel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" List-Id: linux-arch.vger.kernel.org On Mon, Jul 06, 2020 at 08:29:26PM +0200, Peter Zijlstra wrote: > On Mon, Jul 06, 2020 at 09:26:33AM -0700, Paul E. McKenney wrote: > > > And perhaps more constructively, we do need to prioritize address and data > > dependencies over control dependencies. For one thing, there are a lot > > more address/data dependencies in existing code than there are control > > dependencies, and (sadly, perhaps more importantly) there are a lot more > > people who are convinced that address/data dependencies are important. > > If they do not consider their Linux OS running correctly :-) Many of them really do not care at all. In fact, some would consider Linux failing to run as an added bonus. > > For another (admittedly more theoretical) thing, the OOTA scenarios > > stemming from control dependencies are a lot less annoying than those > > from address/data dependencies. > > > > And address/data dependencies are as far as I know vulnerable to things > > like conditional-move instructions that can cause problems for control > > dependencies. > > > > Nevertheless, yes, control dependencies also need attention. > > Today I added one more \o/ Just make sure you continually check to make sure that compilers don't break it, along with the others you have added. ;-) Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:39754 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730051AbgGFSje (ORCPT ); Mon, 6 Jul 2020 14:39:34 -0400 Date: Mon, 6 Jul 2020 11:39:33 -0700 From: "Paul E. McKenney" Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200706183933.GE9247@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200701114027.GO4800@hirez.programming.kicks-ass.net> <20200701140654.GL9247@paulmck-ThinkPad-P72> <20200701150512.GH4817@hirez.programming.kicks-ass.net> <20200701160338.GN9247@paulmck-ThinkPad-P72> <20200702082040.GB4781@hirez.programming.kicks-ass.net> <20200702175948.GV9247@paulmck-ThinkPad-P72> <20200703131330.GX4800@hirez.programming.kicks-ass.net> <20200703144228.GF9247@paulmck-ThinkPad-P72> <20200706162633.GA13288@paulmck-ThinkPad-P72> <20200706182926.GH4800@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200706182926.GH4800@hirez.programming.kicks-ass.net> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Peter Zijlstra Cc: Marco Elver , Nick Desaulniers , Sami Tolvanen , Masahiro Yamada , Will Deacon , Greg Kroah-Hartman , Kees Cook , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , Linux Kbuild mailing list , LKML , linux-pci@vger.kernel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Message-ID: <20200706183933.HPW3TCe5t-8bVumOOdoBp0Or8KcPKN_hyuvQw43sLB8@z> On Mon, Jul 06, 2020 at 08:29:26PM +0200, Peter Zijlstra wrote: > On Mon, Jul 06, 2020 at 09:26:33AM -0700, Paul E. McKenney wrote: > > > And perhaps more constructively, we do need to prioritize address and data > > dependencies over control dependencies. For one thing, there are a lot > > more address/data dependencies in existing code than there are control > > dependencies, and (sadly, perhaps more importantly) there are a lot more > > people who are convinced that address/data dependencies are important. > > If they do not consider their Linux OS running correctly :-) Many of them really do not care at all. In fact, some would consider Linux failing to run as an added bonus. > > For another (admittedly more theoretical) thing, the OOTA scenarios > > stemming from control dependencies are a lot less annoying than those > > from address/data dependencies. > > > > And address/data dependencies are as far as I know vulnerable to things > > like conditional-move instructions that can cause problems for control > > dependencies. > > > > Nevertheless, yes, control dependencies also need attention. > > Today I added one more \o/ Just make sure you continually check to make sure that compilers don't break it, along with the others you have added. ;-) Thanx, Paul