linux-kernel - Re: perf: perf_fuzzer quickly locks up on 4.15-rc7

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Date:   Thu, 11 Jan 2018 14:00:27 -0500 (EST)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
cc:     Peter Zijlstra <peterz@...radead.org>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7

On Wed, 10 Jan 2018, Josh Poimboeuf wrote:

> For the crash, you might try enabling CONFIG_DEBUG_ENTRY and seeing if
> that gives you any output.

I did enable that, didn't seem to help on the haswell machien at least.

> > > > WARNING: can't dereference iret registers at 000000000783fea8 for ip paranoid_entry+0x2e/0x90
> > > > WARNING: can't dereference registers at 00000000f0698d17 for ip paranoid_entry+0x4c/0x90
> > > > WARNING: stack going in the wrong direction? ip=native_sched_clock+0x9/0x90
> 
> This all looks very weird.  The stack pointers -- 000000000783fea8 and
> 00000000f0698d17 -- are obviously very wrong.  I will try to recreate
> locally.

On a related note, on a core2 machine with the perf_fuzzer I got this too:

Jan 11 13:44:01 core2 kernel: [ 1078.931403] WARNING: stack recursion on stack type 4
Jan 11 13:44:01 core2 kernel: [ 1078.931411] WARNING: can't dereference registers at 000000002c6beb99 for ip swapgs_restore_regs_and_return_to_usermode+0x2b/0x7c

Vince