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 32AB0C4332F for ; Fri, 29 Apr 2022 00:09:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353497AbiD2ANK (ORCPT ); Thu, 28 Apr 2022 20:13:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230353AbiD2ANJ (ORCPT ); Thu, 28 Apr 2022 20:13:09 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69F5E7561F; Thu, 28 Apr 2022 17:09:51 -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 ams.source.kernel.org (Postfix) with ESMTPS id 29B02B8327D; Fri, 29 Apr 2022 00:09:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 55FFEC385A9; Fri, 29 Apr 2022 00:09:47 +0000 (UTC) Date: Thu, 28 Apr 2022 20:09:45 -0400 From: Steven Rostedt To: Andrii Nakryiko Cc: Alexei Starovoitov , Masami Hiramatsu , Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Networking , bpf , lkml , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh Subject: Re: [RFC bpf-next 4/4] selftests/bpf: Add attach bench test Message-ID: <20220428200945.5f6a5ba2@gandalf.local.home> In-Reply-To: <20220428195303.6295e90b@gandalf.local.home> References: <20220407125224.310255-1-jolsa@kernel.org> <20220407125224.310255-5-jolsa@kernel.org> <20220412094923.0abe90955e5db486b7bca279@kernel.org> <20220416232103.c0b241c2ec7f2b3b985a2f99@kernel.org> <20220428095803.66c17c32@gandalf.local.home> <20220428160519.04cc40c0@gandalf.local.home> <20220428195303.6295e90b@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, 28 Apr 2022 19:53:03 -0400 Steven Rostedt wrote: > > But that __fentry__ call is not part of __bpf_tramp_exit, actually. > > Whether to call it a bug or limitation is secondary. It marks > > __bpf_tramp_exit as attachable through kprobe/ftrace while it really > > isn't. > > I'm confused by what you mean by "marks __bpf_tramp_exit as attachable"? > What does? Where does it get that information? Does it read > available_filter_functions? OK, I think I see the issue you have. Because the functions shown in available_filter_functions which uses the simple "%ps" to show the function name: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/trace/ftrace.c#n3692 And the code that does the actual matching uses kallsyms_lookup() https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/trace/ftrace.c#n4017 Which appears not to match the function for the address, you can't pass in __bpf_tramp_exit because it wont match the symbol returned by kallsyms_lookup. This does indeed look like a bug in %ps. But in the mean time, I could open code %ps and see if that fixes it. I'll give it try. -- Steve