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=-6.0 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 55004C4361B for ; Wed, 9 Dec 2020 12:37:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1BEDC23B1F for ; Wed, 9 Dec 2020 12:37:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731698AbgLIMgw (ORCPT ); Wed, 9 Dec 2020 07:36:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:46838 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730658AbgLIMgw (ORCPT ); Wed, 9 Dec 2020 07:36:52 -0500 X-Gm-Message-State: AOAM531lcvJWszY8TeZExBsZo9FNXNZjC7fe3OwVODTwKPeXk2KM7BRZ jiCx7zUz/SzbObX35GEbKAI08Z9QnJzCQoIHG+Y= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1607517371; bh=dVBkGQUoTPNqVA5YcFV16WWbYR7ZgobhVlfqccPyMMM=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=QMe8TgyKwG5RwbJWODTsjgFzwi7is/hUW972TN+CJAC8OlmQTclwY4t4o3NpXBDen G0FZuP+wTgQyvKgL79TEeCn1xOpdP8R8eG9kiwnhftkhAUWq2DeAENsJ/WJCalSLmX 6cYxEmgX1SFU23nljhFb8v34P9oCzJdB7O0pfYlFcNm09dy3tMYMu5b+nJNemYg5Sz N7hPMfIRDgpX2Vf/yRRJs7pwXzkUocC+4s1HqFvwpZN6Pp6qIDvgykV8o5KmXOZbzW jmOKI+zRp3XRk3yA4qFqD3H9SW9YHyARfxSDwYAuQREW1ncN6x1r02319tc+Dk+0gL A9YLQ1OTuXCgg== X-Google-Smtp-Source: ABdhPJxvu8VJ4GLgSxlL8PXYZCRvk4pfoOrnmTaMOFmBWsnewmHehKYFMo7e2TQQj/VWUA2w/j4fFIk9/YjD+eZwBUs= X-Received: by 2002:a9d:be1:: with SMTP id 88mr1530396oth.210.1607517370870; Wed, 09 Dec 2020 04:36:10 -0800 (PST) MIME-Version: 1.0 References: <20201201213707.541432-1-samitolvanen@google.com> In-Reply-To: From: Arnd Bergmann Date: Wed, 9 Dec 2020 13:35:54 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v8 00/16] Add support for Clang LTO To: Sami Tolvanen Cc: Masahiro Yamada , Steven Rostedt , Will Deacon , Josh Poimboeuf , Peter Zijlstra , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , Linux Kbuild mailing list , "linux-kernel@vger.kernel.org" , linux-pci Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 8, 2020 at 1:15 PM Arnd Bergmann wrote: > > - one build seems to have dropped all symbols the string operations > from vmlinux, > so while the link goes through, modules cannot be loaded: > ERROR: modpost: "memmove" [drivers/media/rc/rc-core.ko] undefined! > ERROR: modpost: "memcpy" [net/wireless/cfg80211.ko] undefined! > ERROR: modpost: "memcpy" [net/8021q/8021q.ko] undefined! > ERROR: modpost: "memset" [net/8021q/8021q.ko] undefined! > ERROR: modpost: "memcpy" [net/unix/unix.ko] undefined! > ERROR: modpost: "memset" [net/sched/cls_u32.ko] undefined! > ERROR: modpost: "memcpy" [net/sched/cls_u32.ko] undefined! > ERROR: modpost: "memset" [net/sched/sch_skbprio.ko] undefined! > ERROR: modpost: "memcpy" [net/802/garp.ko] undefined! > I first thought this was related to a clang-12 bug I saw the other day, but > this also happens with clang-11 It seems to happen because of CONFIG_TRIM_UNUSED_KSYMS, which is a shame, since I think that is an option we'd always want to have enabled with LTO, to allow more dead code to be eliminated. Arnd