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 38BA7C48BCD for ; Wed, 9 Jun 2021 11:26:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 243EA61108 for ; Wed, 9 Jun 2021 11:26:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239071AbhFIL2J (ORCPT ); Wed, 9 Jun 2021 07:28:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:41296 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239068AbhFIL2G (ORCPT ); Wed, 9 Jun 2021 07:28:06 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0348F61364; Wed, 9 Jun 2021 11:26:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1623237972; bh=bwKCTJMBh6Ibxj2E0Uf9L6+JFaFiSonlIerkAhzvWdQ=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=r2MXSZQJLEr4VGemHwgwzlkGKd7fgIvyVaf5YvBR3TNevzNkl2gDUW9dOJw6oacD/ b9fNtIJqcrkG1vPXT9wrc3UkL28VFgsoBgAYvHUm8w7OMb3JFV4QNQxV80c9JtztHW rLsB81YNiwYKUpz5Ig7rOgckaW0321F6lY8tnk8zPOKa/feOuoGbgUOQvpfnjuxDvV OXLOTpCw1LgXMvm9fkPkjBcmLbYY4UV0CZxZhd0rMP5utoG0RG10daXzo+Y4aw14X7 /aP/p109I2gMfhNacTy/BNiPW2p/Fch3mfULqDF5gstxg6zLFOjD6Cz6hIZEPYwHYi +p1Q1yOBaMcNQ== Received: by mail-wr1-f51.google.com with SMTP id a20so25128510wrc.0; Wed, 09 Jun 2021 04:26:11 -0700 (PDT) X-Gm-Message-State: AOAM53060DQspvdytX0NxVI0+rWXnJCiWAKyZ8CED11J25Q6ih6xqWVC kiLYqMrk0of6sHq2J09VLu16+axV7ycMIXYFqyk= X-Google-Smtp-Source: ABdhPJx+sRKULkqNAMsdkS7ppkuFZIPQoMXMqCYMO9FFaYyX1yp4UcIwfMWpF3c4rXxqa76u9KDl7cdRInH0E4OUgrE= X-Received: by 2002:a5d:4050:: with SMTP id w16mr27735116wrp.99.1623237970528; Wed, 09 Jun 2021 04:26:10 -0700 (PDT) MIME-Version: 1.0 References: <20210204152957.1288448-1-arnd@kernel.org> <20210609110531.GA1528247@roeck-us.net> In-Reply-To: <20210609110531.GA1528247@roeck-us.net> From: Arnd Bergmann Date: Wed, 9 Jun 2021 13:24:18 +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 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. 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. Arnd