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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 1E689C4727E for ; Thu, 1 Oct 2020 18:24:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C25DC20796 for ; Thu, 1 Oct 2020 18:24:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601576659; bh=ZlenZF5zb+iv0OeilUNNdeMsevfR2LkzR3jIcKnQnlY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Sg3/Wf75mf1ssWs39fQXk+4XfOJSM29l2ZvRiMyC9B9nxRIEEGZnwb+V1BSAOPjQ2 NcMh68pMKeOhOn2S3GagVUoaZ3PHcCbSs1i+CAWqzPtN6NqEVlHsOrglqk+7wElw9F UY2YOVt08UqBMS/FgvAoYyeq/5zXRlbb7/jy+kAw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729993AbgJASYT (ORCPT ); Thu, 1 Oct 2020 14:24:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:58272 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729927AbgJASYT (ORCPT ); Thu, 1 Oct 2020 14:24:19 -0400 Received: from quaco.ghostprotocols.net (unknown [179.97.37.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 046AC20754; Thu, 1 Oct 2020 18:24:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601576658; bh=ZlenZF5zb+iv0OeilUNNdeMsevfR2LkzR3jIcKnQnlY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UblmvK4OuUFT3w0XaK6uUERjA6VP++eqDTGxDwYanclmZqbOPHRQxoT2+1PZes/JJ 5QXoKMbQHWPrtb9Z3maxPDT+Ha1Y2hRKOH8LZ8QrdgWBfg9pj/+f4KvSWS9S8a4Dvq 8RbxJNJZ2Ze8zvJv2Xq272VrM6osQQQ8uF4gx9X0= Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id C47AE403AC; Thu, 1 Oct 2020 15:24:15 -0300 (-03) Date: Thu, 1 Oct 2020 15:24:15 -0300 From: Arnaldo Carvalho de Melo To: Alexei Starovoitov Cc: Hao Luo , Arnaldo Carvalho de Melo , Arnaldo Carvalho de Melo , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , dwarves@vger.kernel.org, Yonghong Song , bpf Subject: Re: [PATCH v1] btf_encoder: Handle DW_TAG_variable that has DW_AT_specification Message-ID: <20201001182415.GA101623@kernel.org> References: <20200825004523.1353133-1-haoluo@google.com> <20200826131143.GF1059382@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: dwarves@vger.kernel.org Em Thu, Oct 01, 2020 at 08:47:51AM -0700, Alexei Starovoitov escreveu: > Arnaldo, > > ping. > Is anything blocking this fix from merging? > The kernel patches are stalled waiting on the pahole. Applied locally, testing now, will push to the main branch ASAP. - Arnaldo > Thanks > On Tue, Sep 29, 2020 at 11:52 PM Hao Luo wrote: > > > > Arnaldo, > > > > Is this patch ready to be merged into Pahole's master branch? Alexei > > is testing the kernel patches that need this patch. Please let me know > > if there is anything I can do to help merging. > > > > Thank you, > > Hao > > > > On Wed, Aug 26, 2020 at 6:56 PM Arnaldo Carvalho de Melo > > wrote: > > > > > > > > > > > > On August 26, 2020 3:35:17 PM GMT-03:00, Hao Luo wrote: > > > >Arnaldo, > > > > > > > >On Wed, Aug 26, 2020 at 6:12 AM Arnaldo Carvalho de Melo > > > > wrote: > > > >> > > > >> Em Mon, Aug 24, 2020 at 05:45:23PM -0700, Hao Luo escreveu: > > > >> > It is found on gcc 8.2 that global percpu variables generate the > > > >> > following dwarf entry in the cu where the variable is defined[1]. > > > >> > > > > >> > Take the global variable "bpf_prog_active" defined in > > > >> > kernel/bpf/syscall.c as an example. The debug info for syscall.c > > > >> > has two dwarf entries for "bpf_prog_active". > > > >> > > > > >[...] > > > >> > > > >> Interesting, here I get, with binutils' readelf: > > > >> > > > >> [root@quaco perf]# readelf -wi > > > >../build/v5.8-rc5+/kernel/bpf/syscall.o | grep bpf_prog_active > > > >> DW_AT_name : (indirect string, offset: 0xb70d): > > > >bpf_prog_active > > > >> [root@quaco perf]# > > > >> > > > >> Just one, as: > > > >> > > > >> [root@quaco perf]# readelf -wi > > > >../build/v5.8-rc5+/kernel/bpf/syscall.o | grep bpf_prog_active -B1 -A8 > > > >> <1>: Abbrev Number: 103 (DW_TAG_variable) > > > >> DW_AT_name : (indirect string, offset: 0xb70d): > > > >bpf_prog_active > > > >> DW_AT_decl_file : 11 > > > >> DW_AT_decl_line : 1008 > > > >> DW_AT_decl_column : 1 > > > >> DW_AT_type : <0xcf> > > > >> DW_AT_external : 1 > > > >> DW_AT_declaration : 1 > > > >> <1>: Abbrev Number: 103 (DW_TAG_variable) > > > >> DW_AT_name : (indirect string, offset: 0x3a5d): > > > >bpf_stats_enabled_mutex > > > >> [root@quaco perf]# > > > >> > > > >> I get what you have when I use elfutils' readelf: > > > >> > > > >> [root@quaco perf]# eu-readelf -winfo > > > >../build/v5.8-rc5+/kernel/bpf/syscall.o | grep bpf_prog_active > > > >> name (strp) "bpf_prog_active" > > > >> [ 0] addr .data..percpu+0 > > > >> [root@quaco perf]# > > > >> > > > >> [root@quaco perf]# eu-readelf -winfo > > > >../build/v5.8-rc5+/kernel/bpf/syscall.o | grep -B1 -A8 > > > >\"bpf_prog_active\" > > > >> [ f6a0] variable abbrev: 103 > > > >> name (strp) "bpf_prog_active" > > > >> decl_file (data1) bpf.h (11) > > > >> decl_line (data2) 1008 > > > >> decl_column (data1) 1 > > > >> type (ref4) [ cf] > > > >> external (flag_present) yes > > > >> declaration (flag_present) yes > > > >> [ f6ad] variable abbrev: 103 > > > >> name (strp) "bpf_stats_enabled_mutex" > > > >> [root@quaco perf]# > > > >> > > > >> And: > > > >> > > > >> [root@quaco perf]# eu-readelf -winfo > > > >../build/v5.8-rc5+/kernel/bpf/syscall.o | grep -B5 \ > > > >> [ 1bdf5] variable abbrev: 212 > > > >> specification (ref4) [ f6a0] > > > >> decl_file (data1) syscall.c (1) > > > >> decl_line (data1) 43 > > > >> location (exprloc) > > > >> [ 0] addr .data..percpu+0 > > > >> [root@quaco perf]# > > > >> > > > > > > > >In binutils readelf, there is a extra entry > > > > > > Not here, tomorrow I'll triple check. > > > > > > > > > > > <1><1b24c>: Abbrev Number: 195 (DW_TAG_variable) > > > > <1b24e> DW_AT_specification: <0xf335> > > > > <1b252> DW_AT_decl_file : 1 > > > > <1b253> DW_AT_decl_line : 43 > > > > <1b254> DW_AT_location : 9 byte block: 3 0 0 0 0 0 0 0 0 > > > > (DW_OP_addr: 0) > > > > > > > >which points to > > > > > > > > <1>: Abbrev Number: 95 (DW_TAG_variable) > > > > DW_AT_name : (indirect string, offset: 0xb37a): > > > >bpf_prog_active > > > > > > > >It just doesn't have the string 'bpf_prog_active', annotating entry. > > > >So eu-readelf and binutils readelf have the same results. > > > > > > > >> > Note that second DW_TAG_variable entry contains specification that > > > >> > points to the first entry. > > > >> > > > >> So you are not considering the first when encoding since it is just a > > > >> DW_AT_declaration, considers the second, as it should be, and then > > > >needs > > > >> to go see its DW_AT_specification, right? > > > >> > > > >> Sounds correct, applying, will test further and then push out, > > > >> > > > > > > > >Yes, exactly. The var tags to be considered are those that either have > > > >DW_AT_specification or not have DW_AT_declaration. This makes sure > > > >btf_encoder works correctly on both old and new gcc. > > > > > > > >> Thanks, > > > >> > > > >> - Arnaldo > > > > > > > >Suggested by Yonghong, I tested this change on a larger set of > > > >compilers this time and works correctly. See below. > > > > > > > >Could you also add 'Reported-by: Yonghong Song '? I should > > > >have done that when sending out this patch. The credit goes to > > > >Yonghong. > > > > > > Sure, and I'll add your results with different computers, for the record. > > > > > > Thanks, > > > > > > - Arnaldo > > > > > > > >Thank you, > > > >Hao > > > > > > > > clang 10: > > > > [67] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED > > > > [20168] VAR 'bpf_prog_active' type_id=67, linkage=global-alloc > > > > > > > > clang 9: > > > > [64] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED > > > > [19789] VAR 'bpf_prog_active' type_id=64, linkage=global-alloc > > > > > > > > gcc 10.2 > > > > [18] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED > > > > [20319] VAR 'bpf_prog_active' type_id=18, linkage=global-alloc > > > > > > > > gcc 9.3: > > > > [21] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED > > > > [21085] VAR 'bpf_prog_active' type_id=21, linkage=global-alloc > > > > > > > > gcc 8 > > > > [21] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED > > > > [21084] VAR 'bpf_prog_active' type_id=21, linkage=global-alloc > > > > > > > > gcc 6.2 > > > > [22] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED > > > > [21083] VAR 'bpf_prog_active' type_id=22, linkage=global-alloc > > > > > > > > gcc 4.9 > > > > [17] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED > > > > [20410] VAR 'bpf_prog_active' type_id=17, linkage=global-alloc > > > > > > -- > > > Sent from my Android device with K-9 Mail. Please excuse my brevity. -- - Arnaldo