From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752284AbeCQH5y (ORCPT ); Sat, 17 Mar 2018 03:57:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:57382 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751677AbeCQH5x (ORCPT ); Sat, 17 Mar 2018 03:57:53 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BDB6B20685 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mhiramat@kernel.org Date: Sat, 17 Mar 2018 16:57:50 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Mathieu Desnoyers , Francis Deslauriers , Peter Zijlstra , linux-kernel , Linus Torvalds Subject: Re: [PATCH 2/2] kprobe: fix: Add ftrace_ops_assist_func to kprobe blacklist Message-Id: <20180317165750.3bb30290b2bb47a3052b2700@kernel.org> In-Reply-To: <20180316230154.2d34a98c@vmware.local.home> References: <1500044315-9508-1-git-send-email-francis.deslauriers@efficios.com> <1500044315-9508-3-git-send-email-francis.deslauriers@efficios.com> <20170714142900.1c91949c@gandalf.local.home> <20180316112517.66bdd85a@gandalf.local.home> <229385456.11580.1521217739037.JavaMail.zimbra@efficios.com> <20180316124134.30fa47d5@gandalf.local.home> <20180316124840.3e83bbec@gandalf.local.home> <1577244734.11604.1521222781948.JavaMail.zimbra@efficios.com> <20180317091334.55f1fc325c26deaa4d4a4d19@kernel.org> <20180317102211.a648f26ae0d5a53d95c63022@kernel.org> <20180316230154.2d34a98c@vmware.local.home> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 16 Mar 2018 23:01:54 -0400 Steven Rostedt wrote: > On Sat, 17 Mar 2018 10:22:11 +0900 > Masami Hiramatsu wrote: > > > Or, we can check it by ftrace_location_range() as below patch. > > Cute ;-) > > > > > Note that as a side-effect, we can not trace functions in trace_kprobe.c > > anymore, and this means it is hard to me to make a testcase of kprobe events. > > It was the easiest (and maintainable) way to make test cases... sigh. > > > > ----- > > tracing: kprobes: Prohibit probing on notrace function > > > > From: Masami Hiramatsu > > > > Prohibit kprobe-events probing on notrace function. > > Since probing on the notrace function can cause recursive > > event call. In most case those are just skipped, but > > in some case it falls into infinit recursive call. > > > > Signed-off-by: Masami Hiramatsu > > --- > > kernel/trace/trace_kprobe.c | 23 +++++++++++++++++++++++ > > 1 file changed, 23 insertions(+) > > > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > index 5ce9b8cf7be3..7404b012e51a 100644 > > --- a/kernel/trace/trace_kprobe.c > > +++ b/kernel/trace/trace_kprobe.c > > @@ -487,6 +487,23 @@ disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file) > > return ret; > > } > > > > +#ifdef CONFIG_KPROBES_ON_FTRACE > > +static bool within_notrace_func(struct trace_kprobe *tk) > > +{ > > + unsigned long offset, size, addr; > > + > > + addr = kallsyms_lookup_name(trace_kprobe_symbol(tk)); > > + addr += trace_kprobe_offset(tk); > > + > > + if (!kallsyms_lookup_size_offset(addr, &size, &offset)) > > + return true; /* Out of range. */ > > + > > + return !ftrace_location_range(addr - offset, addr - offset + size); > > +} > > +#else > > +#define within_notrace_func(tk) (false) > > +#endif > > + > > /* Internal register function - just handle k*probes and flags */ > > static int __register_trace_kprobe(struct trace_kprobe *tk) > > { > > @@ -495,6 +512,12 @@ static int __register_trace_kprobe(struct trace_kprobe *tk) > > if (trace_probe_is_registered(&tk->tp)) > > return -EINVAL; > > > > + if (within_notrace_func(tk)) { > > + pr_warn("Could not probe notrace function %s\n", > > + trace_kprobe_symbol(tk)); > > + return -EINVAL; > > + } > > This will prevent probing assembly code. Do we want to do that? Or is > kprobes already prohibited from doing so? No, kprobes itself can probe any assembly code except for the area where can cause recursive hit as I explained. So anyway we still need to mark those functions NOKPROBE_SYMBOL. And note that this just prevent to probe those notrace code *via kprobe_events* interface. So pure kprobe user (like systemtap) is not effected by this change. So, maybe we would better to provide another debug knob which skips above check. This is only for non-experienced admins :) Thanks, > > -- Steve > > > > + > > for (i = 0; i < tk->tp.nr_args; i++) > > traceprobe_update_arg(&tk->tp.args[i]); > > > > > -- Masami Hiramatsu