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 7D1C7C88CB4 for ; Tue, 13 Jun 2023 01:30:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238116AbjFMBav (ORCPT ); Mon, 12 Jun 2023 21:30:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237495AbjFMBav (ORCPT ); Mon, 12 Jun 2023 21:30:51 -0400 X-Greylist: delayed 458 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Mon, 12 Jun 2023 18:30:50 PDT Received: from out-56.mta0.migadu.com (out-56.mta0.migadu.com [IPv6:2001:41d0:1004:224b::38]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A53E170C for ; Mon, 12 Jun 2023 18:30:49 -0700 (PDT) Message-ID: <6a2e8f05-ce2f-bbbb-e6ad-f9db524db997@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1686619387; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Az7NwX67Bf/1j76+8r8hc++AaCY3OLyQFY+NixwvQvo=; b=hz2mq9yqhmWY9nieZx4gzwS/YE9ZWGp0bHn91oSDu5eSjBRB9SRXnmvgpPAJubxIw+lad3 15MT5ruvlPl+He8bSCbg1jwtPCIZyJwsmKxR+IgJJsr5SHdFcFZW+2c8DBNF6KZDPS50ba t/vgfYxefzC2GSqhuwsaeUuBww6SoFA= Date: Tue, 13 Jun 2023 09:22:41 +0800 MIME-Version: 1.0 Subject: Re: [PATCHv2] ftrace: Show all functions with addresses in available_filter_functions_addrs To: Jiri Olsa , Steven Rostedt Cc: Yonghong Song , Masami Hiramatsu , Mark Rutland , Andrii Nakryiko , lkml , linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, Andrii Nakryiko References: <20230611130029.1202298-1-jolsa@kernel.org> <53a11f31-256d-e7bc-eca5-597571076dc5@meta.com> <20230611225407.3e9b8ad2@gandalf.local.home> <20230611225754.01350a50@gandalf.local.home> <20230612110222.50c254f3@gandalf.local.home> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Jackie Liu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org 在 2023/6/13 04:25, Jiri Olsa 写道: > On Mon, Jun 12, 2023 at 11:02:22AM -0400, Steven Rostedt wrote: >> On Mon, 12 Jun 2023 07:49:53 -0700 >> Yonghong Song wrote: >> >>> I am actually interested in how available_filter_functions_addrs >>> will be used. For example, bpf_program__attach_kprobe_multi_opts() >>> can already take addresses from kallsyms. How to use >>> available_filter_functions_addrs to facilitate kprobe_multi? > > the problem is that we need to do 2 passes: > > - through available_filter_functions and find out if the function is traceable > - through /proc/kallsyms to get the address for traceable function > > having available_filter_functions symbols together with addresses allow > us to skip the kallsyms step > > and we are ok with the address in available_filter_functions_addr not being the > function entry, because kprobe_multi uses fprobe and that handles both entry and > patch-site address properly > >>> Do we need to change kernel APIs? It would be great at least we >>> got a RFC patch to answer these questions. >> >> I agree, having that information would also be useful to me. >> >> Jiri? Andrii? > > so we have 2 interfaces how to create kprobe_multi link: > > a) passing symbols to kernel > > 1) user gathers symbols and need to ensure that they are > trace-able -> pass through available_filter_functions file > > 2) kernel takes those symbols and translates them to addresses > through kallsyms api > > 3) addresses are passed to fprobe/ftrace through: > > register_fprobe_ips > -> ftrace_set_filter_ips > > b) passing addresses to kernel > > 1) user gathers symbols and needs to ensure that they are > trace-able -> pass through available_filter_functions file > > 2) user takes those symbols and translates them to addresses > through /proc/kallsyms > > 3) addresses are passed to the kernel and kernel calls: > > register_fprobe_ips > -> ftrace_set_filter_ips > > > The new available_filter_functions_addrs file helps us with option b), > because we can make 'b 1' and 'b 2' in one step - while filtering traceable > functions, we get the address directly. > > I tested the new available_filter_functions_addrs changes with some hacked > selftest changes, you can check it in here [1]. > > I assume Jackie Liu will send new version of her patchset [2] based on this > new available_filter_functions_addrs file. Yes, once the new interface is released, I will release a v2 version patch based on it. -- Jackie Liu > > I think we should have these changes coming together and add some perf > measurements from before and after to make the benefit apparent. > > jirka > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/commit/?h=bpf/avail_addrs&id=fecaeeaf40bae034715ab2e9a46ca1dc16371e8e > [2] https://lore.kernel.org/bpf/20230526155026.1419390-1-liu.yun@linux.dev/#r