linux-kernel - Re: [PATCH -tip v9 7/7] tracing: add kprobe-based event tracer

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Message-ID: <20090605083613.GC4164@in.ibm.com>
Date:	Fri, 5 Jun 2009 14:06:13 +0530
From:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	kvm <kvm@...r.kernel.org>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Christoph Hellwig <hch@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Tom Zanussi <tzanussi@...il.com>
Subject: Re: [PATCH -tip v9 7/7] tracing: add kprobe-based event tracer

On Mon, Jun 01, 2009 at 08:37:54PM -0400, Masami Hiramatsu wrote:
> Add kprobes-based event tracer on ftrace.
> 
> This tracer is similar to the events tracer which is based on Tracepoint
> infrastructure. Instead of Tracepoint, this tracer is based on kprobes(kprobe
> and kretprobe). It probes anywhere where kprobes can probe(this means, all
> functions body except for __kprobes functions).
> 
> Similar to the events tracer, this tracer doesn't need to be activated via
> current_tracer, instead of that, just set probe points via
> /sys/kernel/debug/tracing/kprobe_events. And you can set filters on each
> probe events via /sys/kernel/debug/tracing/events/kprobes/<EVENT>/filter.
> 
> This tracer supports following probe arguments for each probe.
> 
>   %REG  : Fetch register REG
>   sN    : Fetch Nth entry of stack (N >= 0)
>   @ADDR : Fetch memory at ADDR (ADDR should be in kernel)
>   @SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)
>   aN    : Fetch function argument. (N >= 0)
>   rv    : Fetch return value.
>   ra    : Fetch return address.
>   +|-offs(FETCHARG) : fetch memory at FETCHARG +|- offs address.
> 
> See Documentation/trace/kprobes.txt for details.
> 
> Changes from v8:
>  - Fix wrong argument offsets in format.
>  - Remove EVENT_TRACING selection in Kconfig.
>  - Fix debugfs file path.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
> Cc: Christoph Hellwig <hch@...radead.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Tom Zanussi <tzanussi@...il.com>

The kprobe usage look fine.

Tested on x86 and works fine too! Great work, Masami.

Acked-by: Ananth N Mavinakayanahalli <ananth@...ibm.com>
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