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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 B0397C433DF for ; Thu, 25 Jun 2020 08:28:52 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7BC70207E8 for ; Thu, 25 Jun 2020 08:28:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="JfYKQRD6"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="KLWf/lD9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7BC70207E8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=6TXWM5hSghYrjUnZh6G7O2JDizm7384QVn04GpbzRDE=; b=JfYKQRD6AbMXNNK0X005mdYE3 AKA8xjXkVAKNbP+m3PBw5FB1MQw8qvx3yUWmvycrUKDc+wcUiDQGJL+AC37TrePlq67Ej/vI2aihh jW0ZVkWJ5tsGsc/JZJSc1boqkAsGrVXHmYsTex5svIKCDK8oSKyN3dE7XIfXDU3zPtRDyMQho3ccZ NUTzMtG7o99q5tyjCvJoUIsfsI6+S4Ruv8SLRcTKrBOm99CMGSe51NWRkwdwEBHNrIf6ig91d3Jc/ Nuk5Q+FCTnlggAAsFcHnxgTLVmtzfY5mGY4uOhOyjOaU2u9H5DCUUwHT+kS9WNdbgX+yG6U6kl2jw 2Ku4Wr91Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1joNE4-0001n7-D5; Thu, 25 Jun 2020 08:27:16 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1joNE0-0001lx-TH for linux-arm-kernel@lists.infradead.org; Thu, 25 Jun 2020 08:27:13 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AC6FB207E8; Thu, 25 Jun 2020 08:27:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593073632; bh=GncOVRnsRbmrObVuGed/d33M2KDkzxTcEILATAJbLBA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KLWf/lD9VcylMACtq8p1wJiRL0bWr2kYSku0VKCkfSWkCAqHKhXHxHOSwvWTS7j3l w9u9NiMdpF5uccefpWlPwAM4Q9i0V+Qe7aZAsJdNvHebMPPRWYp9leOEenbVEgwE27 4Y8WoUS9Iu/d8VHbgPuJp11WLopn88ZGoDVDvOts= Date: Thu, 25 Jun 2020 09:27:06 +0100 From: Will Deacon To: Sami Tolvanen Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200625082706.GA7584@willie-the-truck> References: <20200624203200.78870-1-samitolvanen@google.com> <20200624211540.GS4817@hirez.programming.kicks-ass.net> <20200624213014.GB26253@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200624213014.GB26253@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, x86@kernel.org, Kees Cook , "Paul E. McKenney" , kernel-hardening@lists.openwall.com, Peter Zijlstra , Greg Kroah-Hartman , Masahiro Yamada , linux-kbuild@vger.kernel.org, Nick Desaulniers , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jun 24, 2020 at 02:30:14PM -0700, Sami Tolvanen wrote: > On Wed, Jun 24, 2020 at 11:15:40PM +0200, Peter Zijlstra wrote: > > On Wed, Jun 24, 2020 at 01:31:38PM -0700, Sami Tolvanen wrote: > > > This patch series adds support for building x86_64 and arm64 kernels > > > with Clang's Link Time Optimization (LTO). > > > > > > In addition to performance, the primary motivation for LTO is to allow > > > Clang's Control-Flow Integrity (CFI) to be used in the kernel. Google's > > > Pixel devices have shipped with LTO+CFI kernels since 2018. > > > > > > Most of the patches are build system changes for handling LLVM bitcode, > > > which Clang produces with LTO instead of ELF object files, postponing > > > ELF processing until a later stage, and ensuring initcall ordering. > > > > > > Note that first objtool patch in the series is already in linux-next, > > > but as it's needed with LTO, I'm including it also here to make testing > > > easier. > > > > I'm very sad that yet again, memory ordering isn't addressed. LTO vastly > > increases the range of the optimizer to wreck things. > > I believe Will has some thoughts about this, and patches, but I'll let > him talk about it. Thanks for reminding me! I will get patches out ASAP (I've been avoiding the rebase from hell, but this is the motivation I need). Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel