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 118ABC433E0 for ; Tue, 9 Feb 2021 19:14:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1A0B64EC7 for ; Tue, 9 Feb 2021 19:14:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233358AbhBITOP (ORCPT ); Tue, 9 Feb 2021 14:14:15 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:36458 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233628AbhBITIX (ORCPT ); Tue, 9 Feb 2021 14:08:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612897583; 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=y13n9ltDuIqN/elDFZtGeflsvqYft3gs4cjirXXX6wE=; b=JGMy/meQ9k9yke+RGbFBQkfj0mHpScL2mMn1RBJoKY6NlgU+uDQ9olNWhVpdsdMoVdiW08 m24khH4D/9ynrAfc7SWwsJ60ca6w2ykY99HGXxRNsMByP5kcl9RGvYp72Vy+jWhdziGn3B I5j0RgRtXtEIGctXOk1D5zNbsSPKnBQ= 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-6-x7-UMDNoN9uQpT5J-jn-3A-1; Tue, 09 Feb 2021 14:06:19 -0500 X-MC-Unique: x7-UMDNoN9uQpT5J-jn-3A-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BFD60107ACE3; Tue, 9 Feb 2021 19:06:16 +0000 (UTC) Received: from krava (unknown [10.40.192.77]) by smtp.corp.redhat.com (Postfix) with SMTP id 762865D749; Tue, 9 Feb 2021 19:06:13 +0000 (UTC) Date: Tue, 9 Feb 2021 20:06:12 +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 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Feb 09, 2021 at 05:13:42PM +0100, Jiri Olsa wrote: > 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 so ftrace data actualy has vfs_truncate address but with extra 4 bytes: ffff80001031f434 real vfs_truncate address: ffff80001031f430 g F .text 0000000000000168 vfs_truncate vfs_truncate disasm: 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 thats why we don't match it in pahole.. I checked few other functions and some have the same problem and some match the function boundary those that match don't have that first hint instrucion, like: ffff800010321e40 : ffff800010321e40: 1f 20 03 d5 nop ffff800010321e44: 1f 20 03 d5 nop ffff800010321e48: 3f 23 03 d5 hint #25 any hints about hint instructions? ;-) jirka