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=-6.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 6E4EBC48BCD for ; Wed, 9 Jun 2021 15:25:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 545C561042 for ; Wed, 9 Jun 2021 15:25:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236258AbhFIP1h (ORCPT ); Wed, 9 Jun 2021 11:27:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:52608 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236251AbhFIP1S (ORCPT ); Wed, 9 Jun 2021 11:27:18 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id F0098613BF; Wed, 9 Jun 2021 15:25:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1623252323; bh=vtYkuK0gwuAmFRZnC/BipTEB3/onfMoeZxcZ8jbvKK4=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=T5nBFtbuBZAg3XVZd08qF+v6Uu6MAIzsYvZ8CF8m0lpJsZRR6h4Omn+LAUufQuagE OxN1OxkCHUp+gdWr+ircp3SpRdEaFx2YjUaVInyuPnEO+DfL5EXLOaUGpzFdJh+Ipu V0bGRXo4QWJr6s8F1eDLNhqPFEgCuIsrmEJ6Pgpo+1RPJRbEbyCe39Ilp2R92bRIpa p4TSjtTbEh3TeCeYW3UARh6YGJHbeHKsbnJf1yx2+VKO3ZUbXbmPvBLb2BJOfi7ec4 l+eyrT7Nh8gx8PHuK/mRV//H2uB72RtLsoubueQSbUhq8QxK7OjMVGlqwujYFWgrzw jbN5Z5XOQxPNQ== Received: by mail-wr1-f52.google.com with SMTP id c5so25909145wrq.9; Wed, 09 Jun 2021 08:25:22 -0700 (PDT) X-Gm-Message-State: AOAM530DOOXYBQ9TXH8e7ZHWEvs1MrxytlUGtfxGM4T56Ulg9IMhAITG yrFf0HkktLfscHNBkWn/CU8OI+NDXU4qCwGBoW0= X-Google-Smtp-Source: ABdhPJxZdHDgCOtt66hi1597iP4beUCl/5c+ssCerXxe6ToZxJkpYR6wfSdYg8zBBcRzVLGRujSJZ7GLeYxxTL53I64= X-Received: by 2002:adf:a28c:: with SMTP id s12mr383873wra.105.1623252321487; Wed, 09 Jun 2021 08:25:21 -0700 (PDT) MIME-Version: 1.0 References: <20210204152957.1288448-1-arnd@kernel.org> <20210609110531.GA1528247@roeck-us.net> <20210609151608.GA3389541@roeck-us.net> In-Reply-To: <20210609151608.GA3389541@roeck-us.net> From: Arnd Bergmann Date: Wed, 9 Jun 2021 17:23:28 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] kallsyms: fix nonconverging kallsyms table with lld To: Guenter Roeck Cc: Linux Kbuild mailing list , Masahiro Yamada , Michal Marek , David Brazdil , Marc Zyngier , Mikhail Petrov , Linux Kernel Mailing List , mfaltesek@google.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 9, 2021 at 5:16 PM Guenter Roeck wrote: > > On Wed, Jun 09, 2021 at 01:24:18PM +0200, Arnd Bergmann wrote: > > On Wed, Jun 9, 2021 at 1:05 PM Guenter Roeck wrote: > > > On Thu, Feb 04, 2021 at 04:29:47PM +0100, Arnd Bergmann wrote: > > > > From: Arnd Bergmann > > > > > > > > ARM randconfig builds with lld sometimes show a build failure > > > > from kallsyms: > > > > > > > > Inconsistent kallsyms data > > > > Try make KALLSYMS_EXTRA_PASS=1 as a workaround > > > > > > > > The problem is the veneers/thunks getting added by the linker extend > > > > the symbol table, which in turn leads to more veneers being needed, > > > > so it may take a few extra iterations to converge. > > > > > > > > This bug has been fixed multiple times before, but comes back every time > > > > a new symbol name is used. lld uses a different set of idenitifiers from > > > > ld.bfd, so the additional ones need to be added as well. > > > > > > > > I looked through the sources and found that arm64 and mips define similar > > > > prefixes, so I'm adding those as well, aside from the ones I observed. I'm > > > > not sure about powerpc64, which seems to already be handled through a > > > > section match, but if it comes back, the "__long_branch_" and "__plt_" > > > > prefixes would have to get added as well. > > > > > > > > > > This is such a whack-a-mole. The problem is hitting us yet again. I suspect > > > it may be due to a new version of lld using new symbols, but I didn't really > > > try to track it down. Is there an easy way to search for missed symbols ? > > > > The way I did it previously was to hack Kbuild to not remove the temporary > > files after a failure, and then compare the "objdump --syms" output of the > > last two stages. > > Problem with that is that we have a non-deterministic problem: The build > fails for us on some build servers, but we are unable to reproduce the > problem when building the same image manually on a development server. > That is similar to what I had observed before, where powerpc builds would > pass on one server, but the same kernel with the same configuration would > fail to build on a second almost identical server. It would really be great > if we can find a better solution. Right, that sucks. I suppose removing the ignore-lists from scripts/kallsyms.c would make it more easily reproducible after a few local randconfig builds, at least enough to add some form of scripting that is able to print the names of the generated symbols. Arnd