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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 autolearn=ham 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 BA8F9C433DB for ; Tue, 26 Jan 2021 02:33:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8103B22B37 for ; Tue, 26 Jan 2021 02:33:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727029AbhAYSkq (ORCPT ); Mon, 25 Jan 2021 13:40:46 -0500 Received: from mail.kernel.org ([198.145.29.99]:57294 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726817AbhAYSjX (ORCPT ); Mon, 25 Jan 2021 13:39:23 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 080EB20665; Mon, 25 Jan 2021 18:38:41 +0000 (UTC) Date: Mon, 25 Jan 2021 13:38:40 -0500 From: Steven Rostedt To: Oleg Nesterov Cc: Jianlin Lv , mingo@redhat.com, mhiramat@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] tracing: precise log info for kretprobe addr err Message-ID: <20210125133840.511b1496@gandalf.local.home> In-Reply-To: <20210125181926.GA10248@redhat.com> References: <20210125160108.2147511-1-Jianlin.Lv@arm.com> <20210125181926.GA10248@redhat.com> 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: linux-kernel@vger.kernel.org On Mon, 25 Jan 2021 19:19:27 +0100 Oleg Nesterov wrote: > On 01/26, Jianlin Lv wrote: > > > > When trying to create kretprobe with the wrong function symbol in tracefs; > > The error is triggered in the register_trace_kprobe() and recorded as > > FAIL_REG_PROBE issue, > > > > Example: > > $ cd /sys/kernel/debug/tracing > > $ echo 'r:myprobe ERROR_SYMBOL_XXX ret=%x0' >> kprobe_events > > bash: echo: write error: Invalid argument > > $ cat error_log > > [142797.347877] trace_kprobe: error: Failed to register probe event > > Command: r:myprobe ERROR_SYMBOL_XXX ret=%x0 > > ^ > > > > This error can be detected in the parameter parsing stage, the effect of > > applying this patch is as follows: > > > > $ echo 'r:myprobe ERROR_SYMBOL_XXX ret=%x0' >> kprobe_events > > bash: echo: write error: Invalid argument > > $ cat error_log > > [415.89]trace_kprobe: error: Retprobe address must be an function entry > > Command: r:myprobe ERROR_SYMBOL_XXX ret=%x0 > > IOW, the "offset != 0" check removed by this patch is obviously wrong, right? > > Agreed, but... > > > --- a/kernel/trace/trace_kprobe.c > > +++ b/kernel/trace/trace_kprobe.c > > @@ -830,7 +830,7 @@ static int trace_kprobe_create(int argc, const char *argv[]) > > flags |= TPARG_FL_RETURN; > > if (kprobe_on_func_entry(NULL, symbol, offset)) > > flags |= TPARG_FL_FENTRY; > > - if (offset && is_return && !(flags & TPARG_FL_FENTRY)) { > > + if (!strchr(symbol, ':') && is_return && !(flags & TPARG_FL_FENTRY)) { > > but why did you add the strchr(':') check instead? > > I was really puzzled until I found the this email from Masami: > https://lore.kernel.org/lkml/20210120131406.5a992c1e434681750a0cd5d4@kernel.org/ > > So I leave this to you and Masami, but perhaps you can document this check at > least in the changelog? > No, you are correct. That needs to be documented in the code. I was about to comment that the check requires a comment ;-) Jianlin, Care to send a v4 of the patch with a comment to why we are checking the symbol for ':'. Thanks! -- Steve