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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 1AC27C433DF for ; Wed, 24 Jun 2020 17:35:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4E4E20738 for ; Wed, 24 Jun 2020 17:35:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GKxzqjwI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405519AbgFXRfN (ORCPT ); Wed, 24 Jun 2020 13:35:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51314 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404908AbgFXRfN (ORCPT ); Wed, 24 Jun 2020 13:35:13 -0400 Received: from mail-qt1-x843.google.com (mail-qt1-x843.google.com [IPv6:2607:f8b0:4864:20::843]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C775EC061573; Wed, 24 Jun 2020 10:35:12 -0700 (PDT) Received: by mail-qt1-x843.google.com with SMTP id o38so2354005qtf.6; Wed, 24 Jun 2020 10:35:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=u71VLQWbO5DL23Y8K+qb6PrSXQwJENiQAs1O7511XBM=; b=GKxzqjwIPzBqXbWSXbHl7RH/IyLS+yYlLaFyGMcmoEkNl2geelNInX2hhzjL00Z7HG yGQV2zZSIRnXkEtNd8DyUVJiIkQ1jH+a5C8kmQ77/qsL7LLYtUg0m8nE/M0nCjfx8zho eawIgP2Jik4cO0z6IWfLm6aGp5C8ZiSRQDq+R9gxF7Xrg4Wu+L7o1Cjhcv0QTmZuI7Ny YiAI9Tvuzjf8kjOJYxFkof/jsj3qf2gamIyMO6Ak9Y22ItX4nzIm3fNmXAnazGsqZVp3 5doNYOpwD8Mp4iQbMItGvcv5PPLdcfQNa4VOdw0HHpvow7TXhAoteneD/7r5ZRRjszzT R1Mg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:date:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=u71VLQWbO5DL23Y8K+qb6PrSXQwJENiQAs1O7511XBM=; b=a6QOk1DWBKkbukjYDPUjFulyyNvSEjXyBZPJQ6FngNn4XPijvdedBHc4o5vvoMgCqs 3TrNVsLhuObwn/3pOih4843C1mMtWJCMoW7ogBPSM9yvg4YlilAZqF8Zzu064nORCUNv 1RbbAadINesdMs7sJ6SzismTgasVkRSh7rpj5SinT8FzxRaX8uyCG3Kql59aKzJtUI96 PUy3ZO4k3TfFe+iJt7YZ7LI91Oo+IUFzcP0QnCYeacyOb4LRzumrL+9wq3nHkJobV6l7 3DbjDv5Qk3joKdCG8RaIanCI03RWbdulm3kQ4Dr4EgCz5b4HCPmZJlRFQ9B5KMzsynmn /wNQ== X-Gm-Message-State: AOAM5327p+zNshOLNiYTMze49Yu/p/gMrhVSI1eJFbAvKUPDJlZeuaaX PD9fQuGYrmuSaXjwmB049ng= X-Google-Smtp-Source: ABdhPJwbxrJtgWRCE11IF50EeMFqChIYm2W1jo8Xv+ODfidD8yDrf4K4eJF8mxRsbCJyvFUCCDnWUg== X-Received: by 2002:ac8:691:: with SMTP id f17mr7816140qth.60.1593020111983; Wed, 24 Jun 2020 10:35:11 -0700 (PDT) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id c191sm3620105qke.114.2020.06.24.10.35.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2020 10:35:11 -0700 (PDT) From: Arvind Sankar X-Google-Original-From: Arvind Sankar Date: Wed, 24 Jun 2020 13:35:09 -0400 To: Fangrui Song Cc: Arvind Sankar , Kees Cook , Will Deacon , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Peter Collingbourne , James Morse , Borislav Petkov , Thomas Gleixner , Ingo Molnar , Russell King , Masahiro Yamada , Nick Desaulniers , Nathan Chancellor , Arnd Bergmann , x86@kernel.org, clang-built-linux@googlegroups.com, linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/9] vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to STABS_DEBUG Message-ID: <20200624173509.GA1460341@rani.riverdale.lan> References: <20200624014940.1204448-1-keescook@chromium.org> <20200624014940.1204448-3-keescook@chromium.org> <20200624153930.GA1337895@rani.riverdale.lan> <20200624161643.73x6navnwryckuit@google.com> <20200624171121.GA1377921@rani.riverdale.lan> <20200624172620.654hhjetiyzpgoxw@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200624172620.654hhjetiyzpgoxw@google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 24, 2020 at 10:26:20AM -0700, Fangrui Song wrote: > > On 2020-06-24, Arvind Sankar wrote: > >On Wed, Jun 24, 2020 at 09:16:43AM -0700, Fangrui Song wrote: > >> > >> On 2020-06-24, Arvind Sankar wrote: > >> >On Tue, Jun 23, 2020 at 06:49:33PM -0700, Kees Cook wrote: > >> >> When linking vmlinux with LLD, the synthetic sections .symtab, .strtab, > >> >> and .shstrtab are listed as orphaned. Add them to the STABS_DEBUG section > >> >> so there will be no warnings when --orphan-handling=warn is used more > >> >> widely. (They are added above comment as it is the more common > >> > > >> >Nit 1: is "after .comment" better than "above comment"? It's above in the > >> >sense of higher file offset, but it's below in readelf output. > >> > >> I mean this order:) > >> > >> .comment > >> .symtab > >> .shstrtab > >> .strtab > >> > >> This is the case in the absence of a linker script if at least one object file has .comment (mostly for GCC/clang version information) or the linker is LLD which adds a .comment > >> > >> >Nit 2: These aren't actually debugging sections, no? Is it better to add > >> >a new macro for it, and is there any plan to stop LLD from warning about > >> >them? > >> > >> https://reviews.llvm.org/D75149 "[ELF] --orphan-handling=: don't warn/error for unused synthesized sections" > >> described that .symtab .shstrtab .strtab are different in GNU ld. > >> Since many other GNU ld synthesized sections (.rela.dyn .plt ...) can be renamed or dropped > >> via output section descriptions, I don't understand why the 3 sections > >> can't be customized. > > > >So IIUC, lld will now warn about .rela.dyn etc only if they're non-empty? > > HEAD and future 11.0.0 will not warn about unused synthesized sections > like .rela.dyn > > For most synthesized sections, empty = unused. > > >> > >> I created a feature request: https://sourceware.org/bugzilla/show_bug.cgi?id=26168 > >> (If this is supported, it is a consistent behavior to warn for orphan > >> .symtab/.strtab/.shstrtab > >> > >> There may be 50% chance that the maintainer decides that "LLD diverges" > >> I would disagree: there is no fundamental problems with .symtab/.strtab/.shstrtab which make them special in output section descriptions or orphan handling.) > >> > > > >.shstrtab is a little special in that it can't be discarded if the ELF > >file contains any sections at all. But yeah, there's no reason they > >can't be renamed or placed in a custom location in the file. > > https://sourceware.org/pipermail/binutils/2020-March/000179.html > proposes -z nosectionheader. With this option, I believe .shstrtab is > not needed. /DISCARD/ : { *(.shstrtab) } should achieve a similar effect. oh wow.