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Date: Tue, 7 Jul 2015 00:00:12 -0400 (EDT)
From: Vince Weaver <vincent.weaver@...ne.edu>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
cc: Vince Weaver <vincent.weaver@...ne.edu>,
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>,
Steven Rostedt <rostedt@...dmis.org>
Subject: Re: perf, kprobes: fuzzer generates huge number of WARNings
On Tue, 7 Jul 2015, Masami Hiramatsu wrote:
> On 2015/07/07 6:27, Vince Weaver wrote:
> > Hello
> >
> > I've been working on trying to get the perf_fuzzer to start fuzzing the
> > PERF_EVENT_IOC_SET_BPF so I've added some really hackish kprobe support.
> >
> > However before I can get to the BPF testing the kprobe code generates a
> > constant stream of WARNINGS which make the machine more or less useless
> > until I stop it. I've included a small selection here.
> >
> > Is this expected?
>
> Did you get same message without BPF hack? And also, could you tell us
> your kernel version and configuration?
It's a Hawell machine running 4.2-rc1. I can post the .config if it's of
interest.
Well the BPF hack is in the fuzzer, not the kernel. And it's not really a
hack, it just turned out to be a huge pain to figure out how to
manually create a valid BPF program in conjunction with a valid kprobe
event.
I did have to sprinkle printks in the kprobe and bpf code to find out
where various EINVAL returns were coming from, so potentially this is just
a problem of printks happening where they shouldn't. I'll remove those
changes and try to reproduce this tomorrow.
This is possibly a long standing issue, until now I never ran the fuzzer
as root so these particular code paths weren't tested.
Vince
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