linux-kernel - Re: perf: fuzzer causes stack going in wrong direction warnings

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Message-ID: <20180510231649.a5p3cv3g653jai6a@treble>
Date:   Thu, 10 May 2018 18:16:49 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Vince Weaver <vincent.weaver@...ne.edu>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: perf: fuzzer causes stack going in wrong direction warnings

On Thu, May 10, 2018 at 03:48:41PM +0200, Peter Zijlstra wrote:
> On Sun, May 06, 2018 at 06:49:35PM -0500, Josh Poimboeuf wrote:
> 
> > Deja vu.  Most of these are related to perf PEBS, similar to the
> > following issue:
> > 
> >   b8000586c90b ("perf/x86/intel: Cure bogus unwind from PEBS entries")
> > 
> > This is basically the ORC version of that.  setup_pebs_sample_data() is
> > assembling a franken-pt_regs which ORC isn't happy about.  RIP is
> > inconsistent with some of the other registers (like RSP and RBP).
> > 
> > Peter, any ideas?
> 
> Urgh..
> 
> Something like so perhaps? It's a bit of a hack, but I couldn't quickly
> think of something nicer.

I had to convert perf_callchain() to a global function to get it to
compile, but it does seem to fix the issue.

-- 
Josh