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=-9.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 32044C04EBF for ; Mon, 3 Dec 2018 19:22:54 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 F201F208A3 for ; Mon, 3 Dec 2018 19:22:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ExENTsCC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F201F208A3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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=bombadil.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=fTXQUHRqSQDIk475jn/v+J7c2jRG3dwJCyxdomzXMVI=; b=ExENTsCCsgl8XA nux2fOz51hTLw5NASXpFMInKdibURx4U4R1/7eE6Jgij6NTawaHZiAeqTE92DSJTgPRZ8QFx6yQqc HHS1IcxyAPFtFOp9CtBt49l5OKC5TrAyTq+uJ6si3AzWc8l0YH292JqsLFs45IqyyBK8r8DYjbyLy TApMYVQoZ5xMEXfkMkUYyBen13k1I/LkYFSMw+Jer4I5lXKAVKNN3nPbR9BWNNQDziAcUAF2qGoVI tcx9YkS7Xo2Ub2NZyDwnKL/kbXsNO96wDzFMSAaQQUoy+9f1NjlJNNGAkqlEz5cNJAu2cWIH5+QOW ORmNyW+ZyhoaMplzCnwQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gTtns-0003qw-HU; Mon, 03 Dec 2018 19:22:48 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gTtnd-0003Rk-Td for linux-arm-kernel@lists.infradead.org; Mon, 03 Dec 2018 19:22:35 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 37647169E; Mon, 3 Dec 2018 11:22:29 -0800 (PST) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 07BD03F575; Mon, 3 Dec 2018 11:22:29 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 11E671AE1062; Mon, 3 Dec 2018 19:22:49 +0000 (GMT) Date: Mon, 3 Dec 2018 19:22:49 +0000 From: Will Deacon To: Nick Desaulniers Subject: Re: [RFT PATCH] arm64: relocatable: build the kernel as a proper shared library Message-ID: <20181203192248.GF29028@arm.com> References: <20181201115324.20847-1-ard.biesheuvel@linaro.org> <20181203170854.GA28218@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20181203_112234_003839_BBA1CB9E X-CRM114-Status: GOOD ( 20.39 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , peter.smith@linaro.org, Linux ARM , Ard Biesheuvel Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Dec 03, 2018 at 10:29:00AM -0800, Nick Desaulniers wrote: > On Mon, Dec 3, 2018 at 9:08 AM Will Deacon wrote: > > > > Hi Ard, > > > > On Sat, Dec 01, 2018 at 12:53:24PM +0100, Ard Biesheuvel wrote: > > > readelf complains about the section layout of vmlinux when building > > > with CONFIG_RELOCATABLE=y (for KASLR): > > > > > > readelf: Warning: [21]: Link field (0) should index a symtab section. > > > readelf: Warning: [21]: Info field (0) should index a relocatable section. > > > > > > Also, it seems that our use of '-pie -shared' is contradictory, and > > > thus ambiguous. In general, the way KASLR is wired up at the moment > > > is highly tailored to how ld.bfd happens to implement (and conflate) > > > PIE executables and shared libraries, so given the current effort to > > > support other toolchains, let's fix some of these issues as well. > > > > > > - Drop the -pie linker argument and just leave -shared. In ld.bfd, > > > the differences between them are unclear (except for the ELF type > > > of the produced image [0]) but lld chokes on seeing both at the > > > same time. > > > > > > - Rename the .rela output section to .rela.dyn, as is customary for > > > shared libraries and PIE executables. > > > > > > - Don't discard the .dynamic, .dynsym, .dynstr and .hash sections. > > > Instead, make sure that they are [mostly] empty by marking all > > > symbols as local, and emit them into the .init segment. > > > > These second two changes seem fairly arbitrary to me: is lld unhappy without > > them? > > I don't know about .rela -> .rela.dyn, or .hash, but LLD developers > just issued patches allowing the following sections to be discarded: > > .dynamic: > https://reviews.llvm.org/D55211 > .dynsym: > https://reviews.llvm.org/D55218 > .dynstr: > https://reviews.llvm.org/D55215 Thanks again. > > My concern is that we'll make some other change in the future and run > > into more arbitrary breakage. Is there any build bots hooked up with lld so > > help us catch regressions quickly? (i.e nightly builds of mainline and next) > > Yes. We're running continuous integration at: > https://github.com/ClangBuiltLinux/continuous-integration > > We have nightly cron jobs building arm64 defconfigs with clang for > mainline, -next, and some LTS branches of the stable tree. ex. > https://travis-ci.com/ClangBuiltLinux/continuous-integration/builds/93312295 Great, that looks very promising! Hopefully that means we can keep things building reliably once we get to that point. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel