Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752208AbbB0G0f (ORCPT ); Fri, 27 Feb 2015 01:26:35 -0500 Received: from mail9.hitachi.co.jp ([133.145.228.44]:48319 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750794AbbB0G0d (ORCPT ); Fri, 27 Feb 2015 01:26:33 -0500 Message-ID: <54F00E13.8060101@hitachi.com> Date: Fri, 27 Feb 2015 15:26:27 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Petr Mladek , Ingo Molnar Cc: "David S. Miller" , Anil S Keshavamurthy , Ananth N Mavinakayanahalli , Frederic Weisbecker , Steven Rostedt , Jiri Kosina , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/7] kprobes: Disable Kprobe when ftrace arming fails References: <1424967232-2923-1-git-send-email-pmladek@suse.cz> <1424967232-2923-2-git-send-email-pmladek@suse.cz> In-Reply-To: <1424967232-2923-2-git-send-email-pmladek@suse.cz> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3651 Lines: 98 (2015/02/27 1:13), Petr Mladek wrote: > arm_kprobe_ftrace() could fail, especially after introducing ftrace IPMODIFY > flag and LifePatching. But this situation is not properly handled. > This patch adds the most important changes. Hmm, as you know, I actually working on it to drop IPMODIFY from kprobes except jprobe. however, yes, that is not enough. We might better set DISABLED flag as this does. > First, it does not make sense to register "kprobe_ftrace_ops" if the filter was > not set. > > Second, we should remove the filter if the registration of "kprobe_ftrace_ops" > fails. The failure might be caused by conflict between the Kprobe and > a life patch via the IPMODIFY flag. If we remove the filter, we will allow > to register "kprobe_ftrace_ops" for another non-conflicting Kprobe later. > > Third, we need to make sure that "kprobe_ftrace_enabled" is incremented only > when "kprobe_ftrace_ops" is successfully registered. Otherwise, another > Kprobe will not try to register it again. Note that we could move the > manipulation with this counter because it is accessed only under "kprobe_mutex". > > Four, we should mark the probe as disabled if the ftrace stuff is not usable. > It will be the correct status. Also it will prevent the unregistration code > from producing another failure. > > It looks more safe to disable the Kprobe directly in "kprobe_ftrace_ops". Note > that we need to disable also all listed Kprobes in case of an aggregated probe. > It would be enough to disable only the new one but we do not know which one it > was. They should be in sync anyway. > Acked-by: Masami Hiramatsu Thank you! > Signed-off-by: Petr Mladek > --- > kernel/kprobes.c | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index ee619929cf90..d1b9db690b9c 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -931,16 +931,33 @@ static int prepare_kprobe(struct kprobe *p) > /* Caller must lock kprobe_mutex */ > static void arm_kprobe_ftrace(struct kprobe *p) > { > + struct kprobe *kp; > int ret; > > ret = ftrace_set_filter_ip(&kprobe_ftrace_ops, > (unsigned long)p->addr, 0, 0); > - WARN(ret < 0, "Failed to arm kprobe-ftrace at %p (%d)\n", p->addr, ret); > - kprobe_ftrace_enabled++; > - if (kprobe_ftrace_enabled == 1) { > + if (WARN(ret < 0, > + "Failed to arm kprobe-ftrace at %p (%d). The kprobe gets disabled.\n", > + p->addr, ret)) > + goto err_filter; > + > + if (!kprobe_ftrace_enabled) { > ret = register_ftrace_function(&kprobe_ftrace_ops); > - WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret); > + if (WARN(ret < 0, > + "Failed to init kprobe-ftrace (%d). The probe at %p gets disabled\n", > + ret, p->addr)) > + goto err_function; > } > + kprobe_ftrace_enabled++; > + return; > + > +err_function: > + ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 1, 0); > +err_filter: > + p->flags |= KPROBE_FLAG_DISABLED; > + if (kprobe_aggrprobe(p)) > + list_for_each_entry_rcu(kp, &p->list, list) > + kp->flags |= KPROBE_FLAG_DISABLED; > } > > /* Caller must lock kprobe_mutex */ > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/