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 4F1F9C77B7C for ; Fri, 5 May 2023 13:20:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232387AbjEENUp (ORCPT ); Fri, 5 May 2023 09:20:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232441AbjEENUo (ORCPT ); Fri, 5 May 2023 09:20:44 -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 CBEA51F4AC; Fri, 5 May 2023 06:20:41 -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 61CA363E15; Fri, 5 May 2023 13:20:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58040C433EF; Fri, 5 May 2023 13:20:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683292840; bh=1tIXs2qrQIkUsmb/r+/EjrPd2vRi0DVKFZc6hOpHua0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nsO0Qsl4rH4ZK0mnu5QCJzz0ti4NCFYq2SRFKkroDjxrXU+3PZNRq7qnUMyIpbVwJ k1E2CTvz1Uhhk9lbMEgn9EmSSiNTr2msESUGLL3RSI/prmW+m1Tbrj8r+jb2AJbG/B L8ls+7GZBtoKdjszRDtbcxUMnmV41xn+XNFE2pa2LkN23ZU5FvyGGx0cc+co/03hQm zAxhiJGOmO3NfRqYP0EEWP1IWMyn7alV652KyRu8PqOCFUxNmru4gr80kjsth01iEM dh3iYtCJsq05V2RzCQnUaT+Tu9+ux5ikFuT1VsBU/WZGml8W8czcMhFAjEbvVy/YhK OeE8Evuwm8SOA== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id B0600403B5; Fri, 5 May 2023 10:20:37 -0300 (-03) Date: Fri, 5 May 2023 10:20:37 -0300 From: Arnaldo Carvalho de Melo To: Namhyung Kim , Andrii Nakryiko , 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 07:01:51PM -0300, Arnaldo Carvalho de Melo escreveu: > 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 one for the recent sample works? >From c6972dae6c962d7be5ba006ab90c9955268debc5 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Fri, 5 May 2023 09:55:18 -0300 Subject: [PATCH 1/2] perf sample_filter.bpf: Stop using vmlinux.h generated by bpftool, use CO-RE Including linux/bpf.h and linux/perf_events.h we get the UAPI structs and then define a subset 'struct perf_sample_data' with the fields we use in this tool while using __attribute__((preserve_access_index)) so that at libbpf load time it can fixup the offsets according to the 'struct perf_data_sample' obtained from the running kernel BTF (/sys/kernel/btf/vmlinux). Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/bpf_skel/sample_filter.bpf.c | 37 +++++++++++++++++++- 1 file changed, 36 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/bpf_skel/sample_filter.bpf.c b/tools/perf/util/bpf_skel/sample_filter.bpf.c index cffe493af1ed5f31..045532c2366d74ef 100644 --- a/tools/perf/util/bpf_skel/sample_filter.bpf.c +++ b/tools/perf/util/bpf_skel/sample_filter.bpf.c @@ -1,12 +1,47 @@ // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) // Copyright (c) 2023 Google -#include "vmlinux.h" +#include +#include #include #include #include #include "sample-filter.h" +// non-UAPI kernel data structures, just the fields used in this tool, +// preserving the access index so that libbpf can fixup offsets with the ones +// used in the kernel when loading the BPF bytecode, if they differ from what +// is used here. + +struct perf_sample_data { + __u64 addr; + __u64 period; + union perf_sample_weight weight; + __u64 txn; + union perf_mem_data_src data_src; + __u64 ip; + struct { + __u32 pid; + __u32 tid; + } tid_entry; + __u64 time; + __u64 id; + struct { + __u32 cpu; + } cpu_entry; + __u64 phys_addr; + __u64 data_page_size; + __u64 code_page_size; +} __attribute__((__aligned__(64))) __attribute__((preserve_access_index)); + +struct bpf_perf_event_data_kern { + struct perf_sample_data * data; + struct perf_event * event; + + /* size: 24, cachelines: 1, members: 3 */ + /* last cacheline: 24 bytes */ +} __attribute__((preserve_access_index)); + /* BPF map that will be filled by user space */ struct filters { __uint(type, BPF_MAP_TYPE_ARRAY); -- 2.39.2