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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 D1E26C43381 for ; Tue, 9 Feb 2021 16:15:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9935E64EB4 for ; Tue, 9 Feb 2021 16:15:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232473AbhBIQP3 (ORCPT ); Tue, 9 Feb 2021 11:15:29 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:53701 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231842AbhBIQPP (ORCPT ); Tue, 9 Feb 2021 11:15:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612887229; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=nnY4e3bu7/a3DG+aVrgYbco1QCGV9rZ/D0QUrkcNoPQ=; b=JohqIKN+DUrgFdoAKz/drYKp1+vssVEhlz1w4MsTtmeqAbzYmkxrqwVawyiZDtnojRV4mA 09QyqiKKP4OabR0/CflnC8vh/mS21mTKiECcx+xd60VeAJVDaEHi6q7fSu9veDgfKtNyki Ovi8cSec0iWeQEIHxjBAX3aQ77UENSY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-360-xaAYfVgPOkWgPiVw3qTkgw-1; Tue, 09 Feb 2021 11:13:45 -0500 X-MC-Unique: xaAYfVgPOkWgPiVw3qTkgw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BD735801979; Tue, 9 Feb 2021 16:13:42 +0000 (UTC) Received: from krava (unknown [10.40.192.77]) by smtp.corp.redhat.com (Postfix) with SMTP id 725F060861; Tue, 9 Feb 2021 16:13:39 +0000 (UTC) Date: Tue, 9 Feb 2021 17:13:38 +0100 From: Jiri Olsa To: Nathan Chancellor Cc: Andrii Nakryiko , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Nick Desaulniers , Networking , bpf , clang-built-linux , Veronika Kabatova , Jiri Olsa Subject: Re: FAILED unresolved symbol vfs_truncate on arm64 with LLVM Message-ID: References: <20210209034416.GA1669105@ubuntu-m3-large-x86> <20210209052311.GA125918@ubuntu-m3-large-x86> <20210209074904.GA286822@ubuntu-m3-large-x86> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Feb 09, 2021 at 04:09:36PM +0100, Jiri Olsa wrote: SNIP > > > > > DW_AT_prototyped (true) > > > > > DW_AT_type (0x01cfdfe4 "long int") > > > > > DW_AT_external (true) > > > > > > > > > > > > > Ok, the problem appears to be not in DWARF, but in mcount_loc data. > > > > vfs_truncate's address is not recorded as ftrace-attachable, and thus > > > > pahole ignores it. I don't know why this happens and it's quite > > > > strange, given vfs_truncate is just a normal global function. > > > > right, I can't see it in mcount adresses.. but it begins with instructions > > that appears to be nops, which would suggest it's traceable > > > > ffff80001031f430 : > > ffff80001031f430: 5f 24 03 d5 hint #34 > > ffff80001031f434: 1f 20 03 d5 nop > > ffff80001031f438: 1f 20 03 d5 nop > > ffff80001031f43c: 3f 23 03 d5 hint #25 > > > > > > > > > > I'd like to understand this issue before we try to fix it, but there > > > > is at least one improvement we can make: pahole should check ftrace > > > > addresses only for static functions, not the global ones (global ones > > > > should be always attachable, unless they are special, e.g., notrace > > > > and stuff). We can easily check that by looking at the corresponding > > > > symbol. But I'd like to verify that vfs_truncate is ftrace-attachable > > I'm still trying to build the kernel.. however ;-) I finally reproduced.. however arm's not using mcount_loc but some other special section.. so it's new mess for me however I tried the same build without LLVM=1 and it passed, so my guess is that clang is doing something unexpected jirka