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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH 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 4AD49C46461 for ; Mon, 30 Jul 2018 07:05:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D8A9F20893 for ; Mon, 30 Jul 2018 07:05:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="fM1Tj7NL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D8A9F20893 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726499AbeG3Iiw (ORCPT ); Mon, 30 Jul 2018 04:38:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:44148 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726399AbeG3Iiw (ORCPT ); Mon, 30 Jul 2018 04:38:52 -0400 Received: from devbox (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 048C320873; Mon, 30 Jul 2018 07:05:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1532934319; bh=7KWuLybK3izgmDITc3mHuyk7G0RGtPD5KyTEWznHhzU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fM1Tj7NLctqr19cYSWzWXvQ38SURGoPIsVnWGg2GYx/5rOndrkxUTgoRwVYe44jKE e1eJ18Sm7dpVSHgZIFON2KltOlYUdEJsjihdyfxDdcIAYICPCbO3DfN1UjdgHiBFhx A1iFgtIMrbkvhDDKCVBFw7EitUYQFJvkVXgt1+40= Date: Mon, 30 Jul 2018 16:05:15 +0900 From: Masami Hiramatsu To: Masami Hiramatsu Cc: rostedt@goodmis.org, Francis Deslauriers , peterz@infradead.org, Shuah Khan , mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 1/3] tracing: kprobes: Prohibit probing on notrace function Message-Id: <20180730160515.c0bc0d564123892182f94310@kernel.org> In-Reply-To: <153278612708.9401.10169488927809009324.stgit@devbox> References: <153278609735.9401.5389431281006205214.stgit@devbox> <153278612708.9401.10169488927809009324.stgit@devbox> 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 28 Jul 2018 22:55:27 +0900 Masami Hiramatsu wrote: > 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. > > This protection can be disabled by the kconfig > CONFIG_KPROBE_EVENTS_ON_NOTRACE=y, but it is highly > recommended to keep it "n" for normal kernel. > > Signed-off-by: Masami Hiramatsu > Tested-by: Francis Deslauriers > --- > Changes in v2 > - Add CONFIG_KPROBE_EVENTS_ON_NOTRACE kconfig for knocking down > the protection. > Changes in v3 > - Fix to check raw-address (no symbol) probe point correctly. > Changes in v4 > - No notrace check if CONFIG_FUNCTION_TRACER=n. In that case > notrace is ignored. Oops, this must be DYNAMIC_FTRACE, not FUNCTION_TRACER, since ftrace_location_range() is provided only if CONFIG_DYNAMIC_FTACE=y. (And CONFIG_DYNAMIC_FTRACE depends on FUNCTION_TRACER) Thanks, > --- > kernel/trace/Kconfig | 18 ++++++++++++++++ > kernel/trace/trace_kprobe.c | 47 +++++++++++++++++++++++++++++++++++-------- > 2 files changed, 56 insertions(+), 9 deletions(-) > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > index dcc0166d1997..24d5a58467a3 100644 > --- a/kernel/trace/Kconfig > +++ b/kernel/trace/Kconfig > @@ -456,6 +456,24 @@ config KPROBE_EVENTS > This option is also required by perf-probe subcommand of perf tools. > If you want to use perf tools, this option is strongly recommended. > > +config KPROBE_EVENTS_ON_NOTRACE > + bool "Do NOT protect notrace function from kprobe events" > + depends on KPROBE_EVENTS > + default n > + help > + This is only for the developers who want to debug ftrace itself > + using kprobe events. > + > + Usually, ftrace related functions are protected from kprobe-events > + to prevent an infinit recursion or any unexpected execution path > + which leads to a kernel crash. > + > + This option disables such protection and allows you to put kprobe > + events on ftrace functions for debugging ftrace by itself. > + Note that this might let you shoot yourself in the foot. > + > + If unsure, say N. > + > config UPROBE_EVENTS > bool "Enable uprobes-based dynamic events" > depends on ARCH_SUPPORTS_UPROBES > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index b37b92e7dbd4..a6ff37a9b65b 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -87,6 +87,21 @@ static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk) > return nhit; > } > > +static nokprobe_inline > +unsigned long trace_kprobe_address(struct trace_kprobe *tk) > +{ > + unsigned long addr; > + > + if (tk->symbol) { > + addr = (unsigned long) > + kallsyms_lookup_name(trace_kprobe_symbol(tk)); > + addr += tk->rp.kp.offset; > + } else { > + addr = (unsigned long)tk->rp.kp.addr; > + } > + return addr; > +} > + > bool trace_kprobe_on_func_entry(struct trace_event_call *call) > { > struct trace_kprobe *tk = (struct trace_kprobe *)call->data; > @@ -99,16 +114,8 @@ bool trace_kprobe_on_func_entry(struct trace_event_call *call) > bool trace_kprobe_error_injectable(struct trace_event_call *call) > { > struct trace_kprobe *tk = (struct trace_kprobe *)call->data; > - unsigned long addr; > > - if (tk->symbol) { > - addr = (unsigned long) > - kallsyms_lookup_name(trace_kprobe_symbol(tk)); > - addr += tk->rp.kp.offset; > - } else { > - addr = (unsigned long)tk->rp.kp.addr; > - } > - return within_error_injection_list(addr); > + return within_error_injection_list(trace_kprobe_address(tk)); > } > > static int register_kprobe_event(struct trace_kprobe *tk); > @@ -487,6 +494,22 @@ disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file) > return ret; > } > > +#if defined(CONFIG_KPROBE_EVENTS_ON_NOTRACE) || \ > + !defined(CONFIG_FUNCTION_TRACER) > +#define within_notrace_func(tk) (false) > +#else > +static bool within_notrace_func(struct trace_kprobe *tk) > +{ > + unsigned long offset, size, addr; > + > + addr = trace_kprobe_address(tk); > + if (!kallsyms_lookup_size_offset(addr, &size, &offset)) > + return true; /* Out of range. */ > + > + return !ftrace_location_range(addr - offset, addr - offset + size); > +} > +#endif > + > /* Internal register function - just handle k*probes and flags */ > static int __register_trace_kprobe(struct trace_kprobe *tk) > { > @@ -495,6 +518,12 @@ 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; > + } > + > for (i = 0; i < tk->tp.nr_args; i++) > traceprobe_update_arg(&tk->tp.args[i]); > > -- Masami Hiramatsu