From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55B13C433E0 for ; Mon, 6 Jul 2020 18:39:53 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id ACA28207BB for ; Mon, 6 Jul 2020 18:39:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="DxcjcPLX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ACA28207BB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-19221-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 27955 invoked by uid 550); 6 Jul 2020 18:39:46 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 27923 invoked from network); 6 Jul 2020 18:39:46 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594060773; bh=C73gOuGPht9dIixGPBoEUXES1WGxsODtcKpLKnFrDqc=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=DxcjcPLXo5KKl20GXi3gR8saz6u7T52XB2h7KY4zD+cFOdG6eQqu/eTW1KOIHVTH1 wju8yVd1Y7IK4dLVkNpXeViYSln0h7JZ5Y1n9IdBD6jdjIrKMxJo0PG6DWDkUmV68w 2PZAalihX+WlZ2m6xkVYthoCCWtQgQAL3RpYBP7s= Date: Mon, 6 Jul 2020 11:39:33 -0700 From: "Paul E. McKenney" 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)" Subject: Re: [PATCH 00/22] add support for Clang LTO 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200706182926.GH4800@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.9.4 (2018-02-28) 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