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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 07B3DC77B7C for ; Thu, 4 May 2023 22:01:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229781AbjEDWB5 (ORCPT ); Thu, 4 May 2023 18:01:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229459AbjEDWB4 (ORCPT ); Thu, 4 May 2023 18:01:56 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FC651988; Thu, 4 May 2023 15:01:55 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2397363A06; Thu, 4 May 2023 22:01:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52E55C433EF; Thu, 4 May 2023 22:01:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683237714; bh=/NJ6Cald5+QS56sCAuNzMM1M5flzPChjXCm5ynFJYQ4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=p+5424SKbXYqbT0mgsI00job7vX+kMoBhiO6zEcFWD7IKK8dKILH1fbHs5VuovBAB TT+aZ8bt+ofbgNFMY7901FzeEEmZhhlQpf3mA+XLKAaKk+YPxW6ORLw4813s8xQknC TrPO6uxIZpR4r+7g9B2jD5rFVKAzqJske9MVvmWAw47OE8mvSQ3NmTJGYSRCa57V4U KwQTL1tKPgqtiSFVrvoLIKk6pmOSOU6ouKxHb6Lct81LJwB5aloJ2y9/wa29s/1CvN QDLkIFpAMMuNuLaQN5xUwoejsI8JsHYk7HC/GxQKQU2jFbCWBrX6LfyZ0khoKc9RsM ppQjhFyyG26rw== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id B05B7403B5; Thu, 4 May 2023 19:01:51 -0300 (-03) Date: Thu, 4 May 2023 19:01:51 -0300 From: Arnaldo Carvalho de Melo To: Andrii Nakryiko , Namhyung Kim , Linus Torvalds Cc: Song Liu , Andrii Nakryiko , Ingo Molnar , Thomas Gleixner , Jiri Olsa , Clark Williams , Kate Carcia , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Adrian Hunter , Changbin Du , Hao Luo , Ian Rogers , James Clark , Kan Liang , Roman Lozko , Stephane Eranian , Thomas Richter , Arnaldo Carvalho de Melo , bpf Subject: Re: BPF skels in perf .Re: [GIT PULL] perf tools changes for v6.4 Message-ID: References: <20230503211801.897735-1-acme@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org Em Thu, May 04, 2023 at 06:48:50PM -0300, Arnaldo Carvalho de Melo escreveu: > Em Thu, May 04, 2023 at 04:07:29PM -0300, Arnaldo Carvalho de Melo escreveu: > > Em Thu, May 04, 2023 at 11:50:07AM -0700, Andrii Nakryiko escreveu: > > > On Thu, May 4, 2023 at 10:52 AM Arnaldo Carvalho de Melo wrote: > > > > Andrii, can you add some more information about the usage of vmlinux.h > > > > instead of using kernel headers? > > > > > I'll just say that vmlinux.h is not a hard requirement to build BPF > > > programs, it's more a convenience allowing easy access to definitions > > > of both UAPI and kernel-internal structures for tracing needs and > > > marking them relocatable using BPF CO-RE machinery. Lots of real-world > > > applications just check-in pregenerated vmlinux.h to avoid build-time > > > dependency on up-to-date host kernel and such. > > > > > If vmlinux.h generation and usage is causing issues, though, given > > > that perf's BPF programs don't seem to be using many different kernel > > > types, it might be a better option to just use UAPI headers for public > > > kernel type definitions, and just define CO-RE-relocatable minimal > > > definitions locally in perf's BPF code for the other types necessary. > > > E.g., if perf needs only pid and tgid from task_struct, this would > > > suffice: > > > > > struct task_struct { > > > int pid; > > > int tgid; > > > } __attribute__((preserve_access_index)); > > > > Yeah, that seems like a way better approach, no vmlinux involved, libbpf > > CO-RE notices that task_struct changed from this two integers version > > (of course) and does the relocation to where it is in the running kernel > > by using /sys/kernel/btf/vmlinux. > > Doing it for one of the skels, build tested, runtime untested, but not > using any vmlinux, BTF to help, not that bad, more verbose, but at least > we state what are the fields we actually use, have those attribute > documenting that those offsets will be recorded for future use, etc. > > Namhyung, can you please check that this works? Second case was simpler: diff --git a/tools/perf/util/bpf_skel/bperf_follower.bpf.c b/tools/perf/util/bpf_skel/bperf_follower.bpf.c index f193998530d431d8..1ab06f2ff5ad7548 100644 --- a/tools/perf/util/bpf_skel/bperf_follower.bpf.c +++ b/tools/perf/util/bpf_skel/bperf_follower.bpf.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) // Copyright (c) 2021 Facebook -#include "vmlinux.h" +#include +#include #include #include #include "bperf_u.h"