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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 5A025C433DB for ; Sun, 7 Mar 2021 06:28:20 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 66D4964EC8 for ; Sun, 7 Mar 2021 06:28:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 66D4964EC8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4DtWkT2zg4z3dHK for ; Sun, 7 Mar 2021 17:28:17 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=permerror (SPF Permanent Error: Unknown mechanism found: ip:192.40.192.88/32) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 4DtWk66SpNz30Gb for ; Sun, 7 Mar 2021 17:27:58 +1100 (AEDT) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 1276NdCi026488; Sun, 7 Mar 2021 00:23:39 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 1276NbRn026484; Sun, 7 Mar 2021 00:23:37 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Sun, 7 Mar 2021 00:23:36 -0600 From: Segher Boessenkool To: Fangrui Song Subject: Re: [PATCH] Replace __toc_start + 0x8000 with .TOC. Message-ID: <20210307062336.GD29191@gate.crashing.org> References: <20210307051433.2756645-1-maskray@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210307051433.2756645-1-maskray@google.com> User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, clang-built-linux Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi! On Sat, Mar 06, 2021 at 09:14:33PM -0800, Fangrui Song wrote: > TOC relocations are like GOT relocations on other architectures. > However, unlike other architectures, GNU ld's ppc64 port defines .TOC. > relative to the .got output section instead of the linker synthesized > .got input section. LLD defines .TOC. as the .got input section plus > 0x8000. When CONFIG_PPC_OF_BOOT_TRAMPOLINE=y, > arch/powerpc/kernel/prom_init.o is built, and LLD computed .TOC. can be > different from __toc_start defined by the linker script. > > Simplify kernel_toc_addr with asm label .TOC. so that we can get rid of > __toc_start. > > With this change, powernv_defconfig with CONFIG_PPC_OF_BOOT_TRAMPOLINE=y > is bootable with LLD. There is still an untriaged issue with Alexey's > configuration. Do you have any explanation why this *does* work, while the original doesn't? Some explanation that says *what* is wrong. To me it doesn't look like the kernel script is. Segher