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=-4.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 D30A3C04EB9 for ; Mon, 3 Dec 2018 18:57:41 +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 A4E67208A3 for ; Mon, 3 Dec 2018 18:57:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="YDkLtPMc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A4E67208A3 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=KQD88x+MAdx8Oc1coGBeYWlYwdv/IFAkSOg60IdX+Cs=; b=YDkLtPMc4kFEAZ Gkrd4NQFEmx859YjIcUGv8cfh0LNukwLf9+7Y6oP6zhYj2yw2e2XpmUYR54luCO417ebyrzegeKhN DEh5fjijLOKAh1w0vlqWcsrMoixuAHn0MCl+c2u2484KUIAwqWDW+ID5azjyajs0yY4RQVuQhYWTQ 7Rq7qt/H0k4N11lboDH+KZiwHSHPBQTtGIZjn7EhkRJO1S/M15Cd8Ttl3X0odLTER3RcqmQTABvzS Rrt5EQYnat81+ikXtB/9MCerMBhgXyASwZwmA8hzalCG+nXmzM3oDTadzVEubeoHL1qP4WZ+dV09Z yMM5m78fJ2nQpDemMgpw==; 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 1gTtPX-0001ZQ-TJ; Mon, 03 Dec 2018 18:57:39 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gTtPU-0001Yo-3l for linux-arm-kernel@lists.infradead.org; Mon, 03 Dec 2018 18:57:37 +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 C33791688; Mon, 3 Dec 2018 10:57:25 -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 92E8F3F59C; Mon, 3 Dec 2018 10:57:25 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 99A861AE1062; Mon, 3 Dec 2018 18:57:45 +0000 (GMT) Date: Mon, 3 Dec 2018 18:57:45 +0000 From: Will Deacon To: Ard Biesheuvel Subject: Re: [RFT PATCH] arm64: relocatable: build the kernel as a proper shared library Message-ID: <20181203185745.GB29028@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_105736_154687_344B54B9 X-CRM114-Status: GOOD ( 21.25 ) 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 , Nick Desaulniers , linux-arm-kernel 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 06:11:47PM +0100, Ard Biesheuvel wrote: > On Mon, 3 Dec 2018 at 18:08, 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? 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) > > > > The .rela.dyn change is for readelf actually, not for lld. Discarding > the .dyn* sections is indeed something lld chokes on. > > It seems reasonable to make the vmlinux ELF image look as much as an > ordinary shared library as we can, to avoid issues with tooling in > general, not just lld. This is why I separated this patch from the one > that caters for lld in particular. Given that the LLD developers are looking at addressing the section discards, can you repost without that part please? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel