linux-kernel - Re: perf, kprobes: fuzzer generates huge number of WARNings

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Date:	Tue, 7 Jul 2015 11:10:09 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: perf, kprobes: fuzzer generates huge number of WARNings

On Tue, 7 Jul 2015 11:06:55 -0400 (EDT)
Vince Weaver <vincent.weaver@...ne.edu> wrote:

> On Tue, 7 Jul 2015, Masami Hiramatsu wrote:
> 
> > > It's a Hawell machine running 4.2-rc1.  I can post the .config if it's of 
> > > interest.
> > 
> > Yes, I'm interested in.
> 
> I've put it here:
> 	http://web.eece.maine.edu/~vweaver/junk/haswell-config
> 
> > OK, and also, if you have a chance, please run the ftracetest as below.
> > 
> > $ cd tools/testing/selftest/ftrace/
> > $ sudo ./ftracetest
> > 
> > This will do a series of basic tests on ftrace and report it.
> 
> It won't run:
> 	sudo ./ftracetest 
> 	Error: No ftrace directory found
> 
> probably because I am running 4.2-rc1 and have tracefs mounted under 
> /sys/kernel/tracing.

You could also just mount debugfs.

> I guess the tester needs to be updated?

Yes, it probably should be.

> I'll see if I can get debugfs mounted too, but I had changed the setup so 
> perf would run.
> 
> 
> When I recompiled my kernel to remove the extra debug messages and run my 
> fuzzer test I get a lot of these, probably because I have the kprobe 
> address hard-coded into the tester.

Probably. If you recompiled the kernel, you need to find the new
address points.

-- Steve

> 
> [  290.067450] Could not insert probe at _text+1664816: -84
> [  290.074976] Probing address(0xffffffff81196730) is not an instruction boundary.
> [  290.131191] Could not insert probe at _text+1664816: -84
> [  290.137555] Probing address(0xffffffff81196730) is not an instruction boundary.
> [  290.170513] Could not insert probe at _text+1664816: -84
> [  290.176877] Probing address(0xffffffff81196730) is not an instruction boundary.
> [  290.298940] Could not insert probe at _text+1664816: -84
> [  290.305224] Probing address(0xffffffff81196730) is not an instruction boundary.
> [  290.349272] Could not insert probe at _text+1664816: -84
> [  290.355585] Probing address(0xffffffff81196730) is not an instruction boundary.
> [  290.365738] Could not insert probe at _text+1664816: -84
> [  290.371992] Probing address(0xffffffff81196730) is not an instruction boundary.
> [  290.383820] perf interrupt took too long (448 > 266), lowering kernel.perf_event_max_sample_rate to 468250
> [  295.088511] perf interrupt took too long (485 > 0), lowering kernel.perf_event_max_sample_rate to 1639281051
> [  311.415309] INFO: rcu_sched detected stalls on CPUs/tasks: { 5} (detected by 6, t=5253 jiffies, g=1818, c=1817, q=534)
> [  311.427531] Task dump for CPU 5:
> [  311.431631] in:imklog       R  running task        0  1736      1 0x00000008
> [  311.439865]  0000000000000286 0000000100000005 0000000000000096 0000000200000000
> [  311.448549]  0000000000000286 ffffffff81c4b2e0 ffffffff81c4b2e0 ffffffff828da234
> [  311.457173]  0000000000001f2f 00007fa62335fe11 0000000000000071 ffffffff828da234
> [  311.465865] Call Trace:
> [  311.469098]  [<ffffffff810c8886>] ? do_syslog+0x456/0x500
> [  311.475518]  [<ffffffff810b02a0>] ? wait_woken+0x90/0x90
> [  311.481830]  [<ffffffff81255bb4>] ? kmsg_read+0x44/0x60
> [  311.488040]  [<ffffffff816a686e>] ? mutex_unlock+0xe/0x10
> [  311.494433]  [<ffffffff81003000>] ? calibrate_delay+0x8f0/0x8f0
> [  311.501356]  [<ffffffff816a98e5>] ? retint_check+0x6/0x12
> [  313.873152] hrtimer: interrupt took 14075878236 ns

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