linux-kernel - Re: perf: perf_fuzzer crashes on Pentium 4 systems

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Date:   Tue, 9 Apr 2019 12:38:25 -0400 (EDT)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Cyrill Gorcunov <gorcunov@...il.com>
cc:     Vince Weaver <vincent.weaver@...ne.edu>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jiri Olsa <jolsa@...hat.com>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: perf: perf_fuzzer crashes on Pentium 4 systems

On Sun, 7 Apr 2019, Cyrill Gorcunov wrote:

> Vince, could you please disable alias events and see if it change
> anything, once you have time? Note once we've aliases disabled the
> counter for cpu cycles get used for NMI watchdog so PERF_COUNT_HW_CPU_CYCLES
> won't be available in "perf" tool itself, but I guess perf_fuzzer uses
> direct kernel syscall.
> ---
>  arch/x86/events/intel/p4.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> Index: linux-tip.git/arch/x86/events/intel/p4.c
> ===================================================================
> --- linux-tip.git.orig/arch/x86/events/intel/p4.c
> +++ linux-tip.git/arch/x86/events/intel/p4.c
> @@ -622,6 +622,8 @@ static u64 p4_get_alias_event(u64 config
>  	u64 config_match;
>  	int i;
>  
> +	return 0;
> +
>  	/*
>  	 * Only event with special mark is allowed,
>  	 * we're to be sure it didn't come as malformed
> 

It still crashes at the same place with this patch and my reproducible 
test case.

Vince