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=-11.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS 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 ADA78C433E0 for ; Tue, 26 Jan 2021 11:01:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 768EC23104 for ; Tue, 26 Jan 2021 11:01:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404676AbhAZLBN (ORCPT ); Tue, 26 Jan 2021 06:01:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:48680 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727404AbhAZEQU (ORCPT ); Mon, 25 Jan 2021 23:16:20 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 757F222B37; Tue, 26 Jan 2021 04:15:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611634539; bh=00fxzqixz3gxH2kqEQtJqETDTQoR1ky557Klu+6Op2g=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=PPfzL4caQKWTOPOorYY7b7BaNX7mAd1UzJj7rFk6dqT1TUmP6xTGSqe5tCpK0Gnf5 qZLiDuISykuKLlzeTyb0Y17W7oM+ZkXCMwTkK9XV+cmIh3/B4dRztY5iidMOTzY5qO RhN8Drr0bXouNNIIKrFwYhzdETcnN1qR8c9+y8rkdwUTE3+bH5PV65DRAJMvaodPFp TMp8CIr6l7OZK2Isi8W/Ks3Q3uO7AgQ2bJyVrY0rikmJoGzjQ5DGGVXiz3JeaEAr3J WW6sBpQvQmv7R+ma94BejyHntOydUIcZFhrrvQMAIuX+zE5pqlw7OAEsLuHzfl56Lm CTspiqeJw6j8w== Date: Tue, 26 Jan 2021 13:15:36 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Oleg Nesterov , 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: <20210126131536.f6e3a737a7b948799084fa7a@kernel.org> In-Reply-To: <20210125133840.511b1496@gandalf.local.home> References: <20210125160108.2147511-1-Jianlin.Lv@arm.com> <20210125181926.GA10248@redhat.com> <20210125133840.511b1496@gandalf.local.home> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; 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 13:38:40 -0500 Steven Rostedt wrote: > 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? > > No, not wrong. Even offset != 0, if the symbol exists in the kernel, kprobe_on_func_entry() will check it. > > 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. Agreed. There should be commented that is defered until the module is loaded. > > 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 ':'. Thank you! > > Thanks! > > -- Steve > -- Masami Hiramatsu