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 8F58EC433E0 for ; Thu, 14 Jan 2021 01:57:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 401AA2343B for ; Thu, 14 Jan 2021 01:57:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728628AbhANB5D (ORCPT ); Wed, 13 Jan 2021 20:57:03 -0500 Received: from mail.kernel.org ([198.145.29.99]:54440 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729558AbhAMXpH (ORCPT ); Wed, 13 Jan 2021 18:45:07 -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 ADD4823370; Wed, 13 Jan 2021 22:48:46 +0000 (UTC) Date: Wed, 13 Jan 2021 17:48:45 -0500 From: Steven Rostedt To: Masami Hiramatsu Cc: "Wangshaobo (bobo)" , , , , , , Subject: Re: [PATCH] kretprobe: avoid re-registration of the same kretprobe earlier Message-ID: <20210113174845.7b1da377@gandalf.local.home> In-Reply-To: <20201222200356.6910b42c165b8756878cc9b0@kernel.org> References: <20201124115719.11799-1-bobo.shaobowang@huawei.com> <20201130161850.34bcfc8a@gandalf.local.home> <20201202083253.9dbc76704149261e131345bf@kernel.org> <9dff21f8-4ab9-f9b2-64fd-cc8c5f731932@huawei.com> <20201215123119.35258dd5006942be247600db@kernel.org> <20201222200356.6910b42c165b8756878cc9b0@kernel.org> 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 Anything more on this? -- Steve On Tue, 22 Dec 2020 20:03:56 +0900 Masami Hiramatsu wrote: > On Mon, 21 Dec 2020 21:31:42 +0800 > "Wangshaobo (bobo)" wrote: > > > Hi steven, Masami, > > We have encountered a problem, when we attempted to use steven's suggestion as following, > > > > >>> If you call this here, you must make sure kprobe_addr() is called on rp->kp. > > >>> But if kretprobe_blacklist_size == 0, kprobe_addr() is not called before > > >>> this check. So it should be in between kprobe_on_func_entry() and > > >>> kretprobe_blacklist_size check, like this > > >>> > > >>> if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset)) > > >>> return -EINVAL; > > >>> > > >>> addr = kprobe_addr(&rp->kp); > > >>> if (IS_ERR(addr)) > > >>> return PTR_ERR(addr); > > >>> rp->kp.addr = addr; > > > > //there exists no-atomic operation risk, we should not modify any rp->kp's information, not all arch ensure atomic operation here. > > > > >>> > > >>> ret = check_kprobe_rereg(&rp->kp); > > >>> if (WARN_ON(ret)) > > >>> return ret; > > >>> > > >>> if (kretprobe_blacklist_size) { > > >>> for (i = 0; > > + ret = check_kprobe_rereg(&rp->kp); > > > > it returns failure from register_kprobe() end called by register_kretprobe() when > > we registered a kretprobe through .symbol_name at first time(through .addr is OK), > > kprobe_addr() called at the begaining of register_kprobe() will recheck and > > failed at following place because at this time we symbol_name is not NULL and addr is also. > > Good catch! Yes, it will reject if both kp->addr and kp->symbol are set. > > > > > static kprobe_opcode_t *_kprobe_addr(const char *symbol_name, > > unsigned int offset) > > { > > if ((symbol_name && addr) || (!symbol_name && !addr)) //we failed here > > > > > > So we attempted to move this sentence rp->kp.addr = addr to __get_valid_kprobe() like this to > > avoid explict usage of rp->kp.addr = addr in register_kretprobe(). > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > index dd5821f753e6..ea014779edfe 100644 > > --- a/kernel/kprobes.c > > +++ b/kernel/kprobes.c > > @@ -1502,10 +1502,15 @@ static kprobe_opcode_t *kprobe_addr(struct kprobe *p) > > static struct kprobe *__get_valid_kprobe(struct kprobe *p) > > { > > struct kprobe *ap, *list_p; > > + void *addr; > > > > lockdep_assert_held(&kprobe_mutex); > > > > - ap = get_kprobe(p->addr); > > + addr = kprobe_addr(p); > > + if (IS_ERR(addr)) > > + return NULL; > > + > > + ap = get_kprobe(addr); > > if (unlikely(!ap)) > > return NULL; > > > > But it also failed when we second time attempted to register a same kretprobe, it is also > > becasue symbol_name and addr is not NULL when we used __get_valid_kprobe(). > > What the "second time" means? If you reuse the kretprobe (and kprobe) you must > reset (cleanup) the kp->addr or kp->symbol_name. That is the initial state. > I think the API should not allow users to enter inconsistent information. > > > > > So it seems has no idea expect for modifying _kprobe_addr() like following this, the reason is that > > the patch 0bd476e6c671 ("kallsyms: unexport kallsyms_lookup_name() and kallsyms_on_each_symbol()") > > has telled us we'd better use symbol name to register but not address anymore. > > > > -static kprobe_opcode_t *_kprobe_addr(kprobe_opcode_t *addr, > > - const char *symbol_name, unsigned int offset) > > +static kprobe_opcode_t *_kprobe_addr(const char *symbol_name, > > + unsigned int offset) > > { > > - if ((symbol_name && addr) || (!symbol_name && !addr)) > > + kprobe_opcode_t *addr; > > + if (!symbol_name) > > goto invalid; > > No, there are cases that the user will set only kp->addr, but no kp->symbol_name. > > > > > For us, this modification has not caused a big impact on other modules, only expects a little > > influence on bpf from calling trace_kprobe_on_func_entry(), it can not use addr to fill in > > rp.kp in struct trace_event_call anymore. > > > > So i want to know your views, and i will resend this patch soon. > > OK, I think it is simpler to check the rp->kp.addr && rp->kp.symbol_name > because it is not allowed (it can lead inconsistent setting). > > How about this code? Is this work for you? > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 41fdbb7953c6..73500be564be 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -2103,6 +2103,14 @@ int register_kretprobe(struct kretprobe *rp) > int i; > void *addr; > > + /* It is not allowed to specify addr and symbol_name at the same time */ > + if (rp->kp.addr && rp->kp.symbol_name) > + return -EINVAL; > + > + /* If only rp->kp.addr is specified, check reregistering kprobes */ > + if (rp->kp.addr && check_kprobe_rereg(&rp->kp)) > + return -EINVAL; > + > if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset)) > return -EINVAL; > > > Thank you, >