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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 E73F5C48BCF for ; Wed, 9 Jun 2021 15:16:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0818613B6 for ; Wed, 9 Jun 2021 15:16:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233134AbhFIPSH (ORCPT ); Wed, 9 Jun 2021 11:18:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229639AbhFIPSG (ORCPT ); Wed, 9 Jun 2021 11:18:06 -0400 Received: from mail-ot1-x32a.google.com (mail-ot1-x32a.google.com [IPv6:2607:f8b0:4864:20::32a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA68FC061574; Wed, 9 Jun 2021 08:16:11 -0700 (PDT) Received: by mail-ot1-x32a.google.com with SMTP id j11-20020a9d738b0000b02903ea3c02ded8so10653739otk.5; Wed, 09 Jun 2021 08:16:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=SqWeZ1nLPj8cBitxoaF2IF1bsXimif+oMVHTeMU3XPs=; b=B2IlJYpjAEhmpcv7JfgrHyGlLIXAIMuTrFRWGQhPhwkyX5Vuo89GHOCuZEnUHsgLNi He3mmlWM7DTWuM0f/aTAEssdjXmzPdXk8EGtrd38WiDKHhu2TXp+MBN0qPb3zug4RQHY 2G0tEgv8kI39Ci+3bLuADtczEhUb1tXhheZNjPXBuK9bPG+hF/qZCLZj9FQEg5N286fx tgfGt0tcuqPW+yZeTfJwvtAIpR35cMNvUlnurv4aOtUAN18S1yG5uIG85+l/MEXAPNV2 03O+cEN9PXBV8rpoumiSdRuD7icAtETd1IYC5f+Lff3JlI9kjwDLrD+ucAJMuQhrNyVC GNLQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=SqWeZ1nLPj8cBitxoaF2IF1bsXimif+oMVHTeMU3XPs=; b=BrvyHF46eYKE5TBm6KlQJUnAWjn9gJOGnesqJxeJ+ymOafyZ995W5Q4nukvXQ9ONmY bAHLMNLf/x2/1oH7mD5rK7C8L7EQmRS9P5zxgg9SJKfD4cNTsCaFomIee9roHhFKMslb 0aNmFi92B74ruAUr719nz30gDhy1UvyTNj1yNNauvyiKAZNalWG/4GpYUhQJTwDiUMn5 VPwdvd/M+sgEnpHMS4B2spBWSBAxkz0sKwZKYg5v2EzT/6j4ecXLm1h2hsFrgRjWeoSf 3etHeWcq93UJQC0YQ/xwmB+o9M2aEuBDe+7pGpTGPtF94y8ra/k7AbICC/BLAfoMcVW+ Sipg== X-Gm-Message-State: AOAM533Rl+V3h5zqlv9Iddut2UAACp8gG+J9mKrJ+XrJXyZQxNGqCkzj eTgDALxZ3pnWwRbatH/Cavk= X-Google-Smtp-Source: ABdhPJzqwC3S+UtqM6z1ytXIUYLmCvD8LsrkL4loVdL28NKYXwv+E5dk5QmnywHEoC53w9lixzkPqA== X-Received: by 2002:a9d:7141:: with SMTP id y1mr7039417otj.15.1623251771072; Wed, 09 Jun 2021 08:16:11 -0700 (PDT) Received: from localhost ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id w20sm49562otl.51.2021.06.09.08.16.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Jun 2021 08:16:10 -0700 (PDT) Sender: Guenter Roeck Date: Wed, 9 Jun 2021 08:16:08 -0700 From: Guenter Roeck To: Arnd Bergmann Cc: Linux Kbuild mailing list , Masahiro Yamada , Michal Marek , David Brazdil , Marc Zyngier , Mikhail Petrov , Linux Kernel Mailing List , mfaltesek@google.com Subject: Re: [PATCH] kallsyms: fix nonconverging kallsyms table with lld Message-ID: <20210609151608.GA3389541@roeck-us.net> References: <20210204152957.1288448-1-arnd@kernel.org> <20210609110531.GA1528247@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > > I suppose we could improve the situation if scripts/link-vmlinux.sh was able > to do that automatically, and compare the kallsyms output .S file between > steps 1 and 2. Comparing the .S files doesn't result in useful data; turns out there are always irrelevant differences. We'll try to run a diff on the output of "objdump --syms". Hopefully that will generate something useful. Thanks, Guenter