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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 AA0E7C4727E for ; Thu, 1 Oct 2020 15:48:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 38F97206A1 for ; Thu, 1 Oct 2020 15:48:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="aN3KKgbU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732213AbgJAPsK (ORCPT ); Thu, 1 Oct 2020 11:48:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732119AbgJAPsJ (ORCPT ); Thu, 1 Oct 2020 11:48:09 -0400 Received: from mail-lf1-x141.google.com (mail-lf1-x141.google.com [IPv6:2a00:1450:4864:20::141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 358EEC0613D0; Thu, 1 Oct 2020 08:48:09 -0700 (PDT) Received: by mail-lf1-x141.google.com with SMTP id y2so7146395lfy.10; Thu, 01 Oct 2020 08:48:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=remczLvi+x2UlaTkRIPOZpcGzrn1dxiqVmUYBRaGrhs=; b=aN3KKgbUNP67F2GvmnY2+gyAdFZ1CaRPh8O3kzT81DYLkLZxtKHHGCWwmkdj23lHoB 5CM5hRRbdSyuIH9yHofBAy8o6kT1RSPWYGvXH8iMR7ksDhbZwajUBIz6z8WbleWNe8il f4AJx6uuR4xzrinzfeHbJUS2jT0HrFJTozXm/lzA0HsqNVqz3J0BZKKzK0lyXMjcAakE vfDyQY64e00EZJ0wezMd+GbI6FfSspclSKa0yLcz7vc0Sa14kL8ysR8+5IG36WXABWXI gamvH/AMhWr/WnzuIDx1UdeKLn3Xlkn0Fo4/FlMc+rLS2iu5PhGrOpN8wX4pn7Bupn21 M4yg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=remczLvi+x2UlaTkRIPOZpcGzrn1dxiqVmUYBRaGrhs=; b=CPuXUEiung8IHr3ijjOoy3dHgjUkSKBZCbSlKfbelAb3z11GPOCxLhf6qfm7anKPjb R97PzC8iLlT1t6+56bZDT159B3Ynx0xlpgB0IInqSW95xkmLlzvv5C6PDk4ca5gqrJa7 uNHJuC6MLRiYHYqjzl41zQkfOyQxksZreKRkz+dRJm3TdShzDF0ZPMpZJOiX9lcL0yr8 aZ78KRJoaPekV4g77iLBnSKXg6IXDDFrRZWWUKoVQLpsWtrrY4d0N4KHp18LxVjYwjZU DLdsLL2KJ2E17jkCLuQNXx6hZ6QWBpWx5PPmhex7u9nNP/Wb061wqFvZYjzJQwB5CbJW sp5w== X-Gm-Message-State: AOAM531spRFQHA8pN6rtKBUy+dV6gj2gQhxxKIJkGgMrJ1VDItfqgP4g nldWoVzFwo+fLRKE+orj1ZJSAjZHfByDH3VLDAI= X-Google-Smtp-Source: ABdhPJzCGDzxPNuyjFKm2llxHRTV6TbYLWP0s/3WLAWeS5aJrLIdEHQ0UckJT13ZVFgKFDCae+uFvIUT8Wz9/IV18xw= X-Received: by 2002:a19:8089:: with SMTP id b131mr2654022lfd.390.1601567285985; Thu, 01 Oct 2020 08:48:05 -0700 (PDT) MIME-Version: 1.0 References: <20200825004523.1353133-1-haoluo@google.com> <20200826131143.GF1059382@kernel.org> In-Reply-To: From: Alexei Starovoitov Date: Thu, 1 Oct 2020 08:47:51 -0700 Message-ID: Subject: Re: [PATCH v1] btf_encoder: Handle DW_TAG_variable that has DW_AT_specification To: Hao Luo , Arnaldo Carvalho de Melo , Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , dwarves@vger.kernel.org, Yonghong Song , bpf Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: dwarves@vger.kernel.org Arnaldo, ping. Is anything blocking this fix from merging? The kernel patches are stalled waiting on the pahole. 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.