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=-7.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 0D59DC43441 for ; Sun, 18 Nov 2018 11:22:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B28B62080F for ; Sun, 18 Nov 2018 11:22:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="RjoJRIuA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B28B62080F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727291AbeKRVmy (ORCPT ); Sun, 18 Nov 2018 16:42:54 -0500 Received: from mail-pf1-f193.google.com ([209.85.210.193]:32876 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726077AbeKRVmx (ORCPT ); Sun, 18 Nov 2018 16:42:53 -0500 Received: by mail-pf1-f193.google.com with SMTP id v68-v6so13484045pfk.0; Sun, 18 Nov 2018 03:22:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=eVIt+uod0BkmtqD5fjD06oV3zi3wkuZnxZRHYBitEcI=; b=RjoJRIuAQC4sI8IzHAwAz/PSmy97Jauxc2AfKYMO+dB6U32pca7vUrkelbEERCEJF1 lekjG4ZFXXe0VG9n8+RuWtoaJBonMVDWU1d5/+kLTBYAlPqqa29PeSHewPKGOLfYsN27 UfYRfyB8UPSPaUCdVks1ekmIMFh1XUWCGLz19P5edXYV1oObqawie4pmFHPnn1Wa/K8g RK6oDlTClz5z4VV+90ZH41j8mgkzrvPgqzOxMoSSmKwv9zS2Y01RFV7mzjVEaJQJnWpJ cJjkeCFoBw5YP+d4DR5biQMPu7ILMJSPbeT9LIc3j4ogQVshwueiQKD+rmMutuxzbxPK 7llA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=eVIt+uod0BkmtqD5fjD06oV3zi3wkuZnxZRHYBitEcI=; b=mZziq45ASDG9i2j0CJIfVpnOF/A7mdQ7dTaqw8BE4+Bf0S6cahsVZbUf2ovgvaWzwG xW4G5PM0UQnGBKWpvVmU0n+FjFr8qlgL2OIOPlDYXG74UFoUMjhCU89GSXjfzrl/ipUn z/KqCFJQ7v/Vs2Rx4Omh3GYivZe5V716T7zaROLsdUJxDlgEryJtM559ryf7yCf07R00 zrs20lK40t5pxBkx8ChnZI0yHAMa8e7NksGoQkDOlz4iuEMuCacKRMHlxNryxNYAJIiR 67BZU3WgPHsl3BVMgqP6Hb4aHOdWVbv5v3d0i8opPzCqvV7+tMxYLe9gse011hdaMa5M k/Pw== X-Gm-Message-State: AGRZ1gJng26MOk8wD0tMVeoXoPTASmlZSxdskz0NDy47V8nkcKeX+LQm 5Z0s3Qng9qpwU+lHbU6ugYhcgZkR X-Google-Smtp-Source: AJdET5dCOURk+Kjd7LMbYSjWLm3N+tpgF+0yZqFy0BEGz8tAFu5qd2j6uoDNzfdswqmVuUOlo5EfMQ== X-Received: by 2002:a62:f54f:: with SMTP id n76mr18565573pfh.59.1542540169376; Sun, 18 Nov 2018 03:22:49 -0800 (PST) Received: from bubble.grove.modra.org ([58.175.241.133]) by smtp.gmail.com with ESMTPSA id b62-v6sm41907018pfa.159.2018.11.18.03.22.47 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 18 Nov 2018 03:22:48 -0800 (PST) Received: by bubble.grove.modra.org (Postfix, from userid 1000) id 8D09580D2B; Sun, 18 Nov 2018 21:52:44 +1030 (ACDT) Date: Sun, 18 Nov 2018 21:52:44 +1030 From: Alan Modra To: Michael Ellerman Cc: Joel Stanley , Stephen Rothwell , Benjamin Herrenschmidt , linuxppc-dev@lists.ozlabs.org, Linux-Next Mailing List , Linux Kernel Mailing List Subject: Re: linux-next: build warnings from Linus' tree Message-ID: <20181118112244.GD21617@bubble.grove.modra.org> References: <20180612081413.323d85b8@canb.auug.org.au> <87k1lgufiw.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k1lgufiw.fsf@concordia.ellerman.id.au> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 14, 2018 at 09:20:23PM +1100, Michael Ellerman wrote: > Joel Stanley writes: > > Hello Alan, > > > > On Tue, 12 Jun 2018 at 07:44, Stephen Rothwell wrote: > > > >> Building Linus' tree, today's linux-next build (powerpc ppc64_defconfig) > >> produced these warning: > >> > >> ld: warning: orphan section `.gnu.hash' from `linker stubs' being placed in section `.gnu.hash'. > >> ld: warning: orphan section `.gnu.hash' from `linker stubs' being placed in section `.gnu.hash'. > >> ld: warning: orphan section `.gnu.hash' from `linker stubs' being placed in section `.gnu.hash'. > >> > >> This may just be because I have started building using the native Debian > >> gcc for the powerpc builds ... > > > > Do you know why we started creating these? > > It's controlled by the ld option --hash-style, which AFAICS still > defaults to sysv (generating .hash). > > But it seems gcc can be configured to have a different default, and at > least my native ppc64le toolchains are passing gnu, eg: > > /usr/lib/gcc/powerpc64le-linux-gnu/6/collect2 -plugin > /usr/lib/gcc/powerpc64le-linux-gnu/6/liblto_plugin.so > -plugin-opt=/usr/lib/gcc/powerpc64le-linux-gnu/6/lto-wrapper > -plugin-opt=-fresolution=/tmp/ccw1U2fF.res > -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s > -plugin-opt=-pass-through=-lc -plugin-opt=-pass-through=-lgcc > -plugin-opt=-pass-through=-lgcc_s --sysroot=/ --build-id --eh-frame-hdr > -V -shared -m elf64lppc > --hash-style=gnu > ^^^^^^^^^^^^^^^^ > > So that's presumably why we're seeing it, some GCCs are configured to > use it. > > > If it's intentional, should we be putting including them in the same > > way as .hash sections? > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/kernel/vmlinux.lds.S#n282 > > > > .hash : AT(ADDR(.hash) - LOAD_OFFSET) { *(.hash) } > > That would presumably work. > > My question though is do we even need it? > > >From what I can see for it to be useful you need the section as well as > an entry in the dynamic section pointing at it, and we don't have a > dynamic section at all: > > $ readelf -S vmlinux | grep gnu.hash > [ 4] .gnu.hash GNU_HASH c000000000dbbdb0 00dcbdb0 > $ readelf -d vmlinux > > There is no dynamic section in this file. > > Compare to the vdso: > > $ readelf -d arch/powerpc/kernel/vdso64/vdso64.so > > Dynamic section at offset 0x868 contains 12 entries: > Tag Type Name/Value > 0x000000000000000e (SONAME) Library soname: [linux-vdso64.so.1] > 0x0000000000000004 (HASH) 0x120 > 0x000000006ffffef5 (GNU_HASH) 0x170 > 0x0000000000000005 (STRTAB) 0x320 > 0x0000000000000006 (SYMTAB) 0x1d0 > 0x000000000000000a (STRSZ) 269 (bytes) > 0x000000000000000b (SYMENT) 24 (bytes) > 0x0000000070000003 (PPC64_OPT) 0x0 > 0x000000006ffffffc (VERDEF) 0x450 > 0x000000006ffffffd (VERDEFNUM) 2 > 0x000000006ffffff0 (VERSYM) 0x42e > 0x0000000000000000 (NULL) 0x0 > > > So can't we just discard .gnu.hash? And in fact do we need .hash either? > > Actually arm64 discards the latter, and parisc discards both. > > Would still be good to hear from Alan or someone else who knows anything > about toolchain stuff, ie. not me :) .gnu.hash, like .hash, is used by glibc ld.so for dynamic symbol lookup. I imagine you don't need either section in a kernel, so discarding both sounds reasonable. Likely you could discard .interp and .dynstr too, and .dynsym when !CONFIG_PPC32. -- Alan Modra Australia Development Lab, IBM