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, URIBL_BLOCKED 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 57FE2C433DF for ; Wed, 24 Jun 2020 17:11:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3267F2082F for ; Wed, 24 Jun 2020 17:11:30 +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="T4re3FJY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405229AbgFXRL0 (ORCPT ); Wed, 24 Jun 2020 13:11:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405156AbgFXRL0 (ORCPT ); Wed, 24 Jun 2020 13:11:26 -0400 Received: from mail-qv1-xf43.google.com (mail-qv1-xf43.google.com [IPv6:2607:f8b0:4864:20::f43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8900C061573; Wed, 24 Jun 2020 10:11:24 -0700 (PDT) Received: by mail-qv1-xf43.google.com with SMTP id h18so1395515qvl.3; Wed, 24 Jun 2020 10:11:24 -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=9YWMqwXjT5S6VAJIIaXravD3PBhiNi6VxmnHUwPk58o=; b=T4re3FJYILiDhz9PkEeru3WH+A8mIoGMSUfmqoPylClN1ucQbubgZwRaYB//PJ1fJa euX9ascn/HJ4kkLOgNypOY0irZn+1ylEhqG7wpZQDUmMqD++X0xBN8IvMGiotsKaJUYA vtraez/F8i7l/59H6Hv4bxYueuGKEO5/sbMgRy4TG5SyWgthFeJLkMSX06lS7H43qTEB jNBYNPvnx3B0yKQliUd7xQI9Gm/1cYM9hE/Q6SpRUDqZDF+IEs7llywzUVDfkbw6XclN VWaeMysZoB4WNQXs5/R8rYxiII0emUxuktYCxwj7DnB6YfSvuYwteQvU2/6dfvkCxWV+ 7M4g== 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=9YWMqwXjT5S6VAJIIaXravD3PBhiNi6VxmnHUwPk58o=; b=feRHL4gUdvlRWDtg9jadNMtsYmGeto68fPkOf8/sl8J5uaRGzJlBeRvyBHtxUttuG+ 3xbQGjWl2zQaBDD/3uNbwmyhdD/i7EvlTNMmdPmkcOxg4VC2oqBZatWhaCaOc1Z2eBhU 16VvZrcNX/W4UyxveBzcSmNGX2vXSg4e2rf083PKuIrtc1TYgOrz15v7cX8IEBYKhlqM Mr82R/echkMhXtiotyFBdkZKw2QMoPb/+Ox36+fBCoJAx/XE2/4LzI1GARKR+1XV/QLt lpAE97x1scJ4CsdNNHXdwMBzFqR6lIPA10VgBmY5IDLQHEB+7du90+ta+DgtFIAbxwew 6iTw== X-Gm-Message-State: AOAM5312y1pv1qZL4YmXSbuqB07AuUtooXfvGrAgRkzz8fhGovn/3K7/ mxdcRaJOnvdg6HSexlrW/6E= X-Google-Smtp-Source: ABdhPJzzcFnkfc+tA2tOjjPS8V3pkJ6470qOFNUn3CmU7YZPddDvdZojC2NjkoNgT0+kvlBrLxUj/A== X-Received: by 2002:a0c:ed31:: with SMTP id u17mr30837447qvq.117.1593018683766; Wed, 24 Jun 2020 10:11:23 -0700 (PDT) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id c2sm3746366qkl.58.2020.06.24.10.11.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2020 10:11:23 -0700 (PDT) From: Arvind Sankar X-Google-Original-From: Arvind Sankar Date: Wed, 24 Jun 2020 13:11:21 -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: <20200624171121.GA1377921@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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200624161643.73x6navnwryckuit@google.com> Sender: linux-efi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org 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? > > 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.