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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 03E9FC433E0 for ; Wed, 27 Jan 2021 13:30:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B9324207B5 for ; Wed, 27 Jan 2021 13:30:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238353AbhA0Nag (ORCPT ); Wed, 27 Jan 2021 08:30:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:58948 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238422AbhA0N23 (ORCPT ); Wed, 27 Jan 2021 08:28:29 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5164C207A0; Wed, 27 Jan 2021 13:27:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611754067; bh=EbCIlPU9f5xBqJq67mxctKmNjWlGB44crWtH0kvcGfM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fHlu3bwPTYx3PqpRgp+nbOJxtggwEoEQ/xSt/QeqBRodDyilH5XthGA6wKi0e/wGS Na6AAWF57kikHmjH9xmty78K+8xATWlP1mRIsZIHlrTK+69B0lxBckWg305ub5PuLu AYqv2Vvh8HE5A4AcaljWXkZ4gNeDS8ed/P0p6ZiqrmHZfIAZlbJzsuIr1xKFD/ZzMX BEsP3X1GkZzHcRpkBYWNMEw144i9s1B2GNbJNJE1kCN4JGf/ZFdtBsVc8g+SRSvjSZ UWMp2r6v0+Z1GvSKuuLNEbt3ODHFuebTdAHSu2FtD+YzMSJVrM/eLV2vdJpIEOTCot aQzuEHX6Z1Pxw== Date: Wed, 27 Jan 2021 22:27:43 +0900 From: Masami Hiramatsu To: Jianlin Lv Cc: Oleg Nesterov , Steven Rostedt , "mingo@redhat.com" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3] tracing: precise log info for kretprobe addr err Message-Id: <20210127222743.771338cf7f89fb0b78dd838c@kernel.org> In-Reply-To: References: <20210125160108.2147511-1-Jianlin.Lv@arm.com> <20210125181926.GA10248@redhat.com> <20210125133840.511b1496@gandalf.local.home> <20210126131536.f6e3a737a7b948799084fa7a@kernel.org> <20210126202058.GC12469@redhat.com> <20210127110226.a65b3e8c66eeab6ee63f8aee@kernel.org> 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 Wed, 27 Jan 2021 02:46:10 +0000 Jianlin Lv wrote: > > > > -----Original Message----- > > From: Masami Hiramatsu > > Sent: Wednesday, January 27, 2021 10:02 AM > > To: Oleg Nesterov > > Cc: Steven Rostedt ; Jianlin Lv ; > > mingo@redhat.com; linux-kernel@vger.kernel.org > > Subject: Re: [PATCH v3] tracing: precise log info for kretprobe addr err > > > > On Tue, 26 Jan 2021 21:20:59 +0100 > > Oleg Nesterov wrote: > > > > > On 01/26, Masami Hiramatsu wrote: > > > > > > > > > > > > > > > > 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. > > > > > > Yes, but unless I am totally confused... if kprobe_on_func_entry() > > > returns false, then trace_kprobe_create() should fail with BAD_RETPROBE > > even if offset == 0 ? > > > > Yes, if kprobe_on_func_entry() returns false, register_kretprobe() also > > returns an error. > > > > ----- > > int register_kretprobe(struct kretprobe *rp) { > > int ret = 0; > > struct kretprobe_instance *inst; > > int i; > > void *addr; > > > > if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp- > > >kp.offset)) > > return -EINVAL; > > > > ----- > > > > Thank you, > > > > -- > > Masami Hiramatsu > > > If register_kretprobe()returns an error -EINVAL. > This means that __register_trace_kprobe return -EINVAL, > > --- > ret = __register_trace_kprobe(tk); > if (ret == -ENOENT && !trace_kprobe_module_exist(tk)) { > pr_warn("This probe might be able to register after target module is loaded. Continue.\n"); > ret = 0; > } > --- > As code show, cannot enable kretprobe for an unloaded module. > > This is consistent with my test results (no VXLAN module is loaded). > > # perf probe -m /lib/modules/5.11.0-rc2+/kernel/drivers/net/vxlan.ko \ > 'vxlan_xmit%return $retval' > Failed to write event: Invalid argument > Error: Failed to add events. > > Is this a bug? Oops, good catch! It seems that the bug has been introduced when I added kprobe_on_func_entry() to register_Kretprobe. Let me fix it. Thank you! -- Masami Hiramatsu