linux-kernel - Re: [PATCH v3 0/5] ARM64: Add kernel probes(Kprobes) support

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Message-ID: <CAPvkgC3=KKKMa1hWdOYOcV7D7kQSLtnNnXLBB64_P-V+_qUwTw@mail.gmail.com>
Date:	Thu, 4 Dec 2014 10:21:33 +0000
From:	Steve Capper <steve.capper@...aro.org>
To:	David Long <dave.long@...aro.org>
Cc:	William Cohen <wcohen@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"Jon Medhurst (Tixy)" <tixy@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	David Miller <davem@...emloft.net>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 0/5] ARM64: Add kernel probes(Kprobes) support

On 4 December 2014 at 02:48, David Long <dave.long@...aro.org> wrote:
> On 12/03/14 20:16, William Cohen wrote:
>
> [...]
>
>>
>> The perf issue seems to be independent and can be reproduced without using
>> any kprobe support.  I need to get a simple reproducer and mention it on the
>> linux-perf-user list.
>>
>> -Will
>>
>
>
> OK, my confusion came from all the different things perf can use.  I have
> not yet been able to reproduce the "perf stat" failure, but I do see the
> failure with Steve's example using tracepoints.  I had thought that was
> using kprobes, but apparently it just uses tracepoints.  These look like two
> different failures to me:  One related to tracepoints, and one in the PMU
> driver.
>
> Since this seems unrelated to kprobes I don't plan on pursuing these
> particular problems.
>
> -dl
>

Sorry for the late reply...

The example I had was:
echo "p:memcpy memcpy %x2" > /sys/kernel/debug/tracing/kprobe_events
perf record -e kprobes:memcpy -a sleep 5

[then crash due to IRQs being unexpectedly disabled in the ext4 code]

Isn't that a kprobe problem?

Cheers,
--
Steve
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