linux-kernel - RE: [RFC][PATCH 2/6] perf, arch: Rework perf_event

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Date:	Tue, 22 Nov 2011 13:25:16 +0100
From:	Oleg Strikov <OSTRIKOV@...dia.com>
To:	Will Deacon <will.deacon@....com>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"mingo@...e.hu" <mingo@...e.hu>, William Cohen <wcohen@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Michael Cree <mcree@...on.net.nz>,
	Deng-Cheng Zhu <dengcheng.zhu@...il.com>,
	Anton Blanchard <anton@...ba.org>,
	Eric B Munson <emunson@...bm.net>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	"David S. Miller" <davem@...emloft.net>,
	Richard Kuo <rkuo@...eaurora.org>,
	Stephane Eranian <eranian@...gle.com>,
	Arun Sharma <asharma@...com>, Vince Weaver <vince@...ter.net>
Subject: RE: [RFC][PATCH 2/6] perf, arch: Rework perf_event_index()

> Actually, the registers for controlling interrupts aren't visible to userspace with ARMv7. On ARMv6, this is a different story, which is why I didn't mention doing this > for older platforms earlier :)

Yes. But the profiling tool enables the interrupts.
I mean that with the profiler running the bad application can break the system.

Oleg

-----Original Message-----
From: Will Deacon [mailto:will.deacon@....com] 
Sent: Tuesday, November 22, 2011 4:14 PM
To: Oleg Strikov
Cc: Peter Zijlstra; mingo@...e.hu; William Cohen; linux-kernel@...r.kernel.org; Michael Cree; Deng-Cheng Zhu; Anton Blanchard; Eric B Munson; Heiko Carstens; Paul Mundt; David S. Miller; Richard Kuo; Stephane Eranian; Arun Sharma; Vince Weaver
Subject: Re: [RFC][PATCH 2/6] perf, arch: Rework perf_event_index()

On Tue, Nov 22, 2011 at 12:00:33PM +0000, Oleg Strikov wrote:
> Also, please do not forget that enabling the userspace access to the 
> counters may not only create some problems to the profilers like Perf/OProfile but could also trash the kernel with the interrupts.

Actually, the registers for controlling interrupts aren't visible to userspace with ARMv7. On ARMv6, this is a different story, which is why I didn't mention doing this for older platforms earlier :)

Anyway, this thread has digressed now so you can always jump onto the ARM list (linux-arm-kernel) if you want to discuss this more.

Cheers,

Will
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