linux-kernel - [PATCH tracing/kprobes 6/6] tracing/kprobes: Disable kprobe events by default

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Date:	Mon, 14 Sep 2009 16:49:37 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>,
	lkml <linux-kernel@...r.kernel.org>
Cc:	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Christoph Hellwig <hch@...radead.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Jason Baron <jbaron@...hat.com>,
	"K.Prasad" <prasad@...ux.vnet.ibm.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Tom Zanussi <tzanussi@...il.com>
Subject: [PATCH tracing/kprobes 6/6] tracing/kprobes: Disable kprobe events by
	default

Disable newly created kprobe events by default, not to disturb
another user using ftrace. "Disturb" means when someone using
ftrace and another user tries to use perf-tools, (in near
future) if he defines new kprobe event via perf-tools, then new
events will mess up the frace buffer. I think that's ugly.


Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
c: Jim Keniston <jkenisto@...ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Frank Ch. Eigler <fche@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Jason Baron <jbaron@...hat.com>
Cc: K.Prasad <prasad@...ux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@...fujitsu.com>
Cc: Li Zefan <lizf@...fujitsu.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Tom Zanussi <tzanussi@...il.com>
---

 Documentation/trace/kprobetrace.txt |   11 +++++++++--
 kernel/trace/trace_kprobe.c         |    4 ++--
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 6521681..9b8f7c6 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -122,8 +122,15 @@ print fmt: "(%lx) dfd=%lx filename=%lx flags=%lx mode=%lx", REC->ip, REC->dfd, R
 
   echo > /sys/kernel/debug/tracing/kprobe_events
 
- This clears all probe points. and you can see the traced information via
-/sys/kernel/debug/tracing/trace.
+ This clears all probe points.
+
+ Right after definition, each event is disabled by default. For tracing these
+events, you need to enable it.
+
+  echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable
+  echo 1 > /sys/kernel/debug/tracing/events/kprobes/myretprobe/enable
+
+ And you can see the traced information via /sys/kernel/debug/tracing/trace.
 
   cat /sys/kernel/debug/tracing/trace
 # tracer: nop
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index d8db935..f6821f1 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -383,7 +383,7 @@ static int register_trace_probe(struct trace_probe *tp)
 		goto end;
 	}
 
-	tp->flags = TP_FLAG_TRACE;
+	tp->rp.kp.flags |= KPROBE_FLAG_DISABLED;
 	if (probe_is_return(tp))
 		ret = register_kretprobe(&tp->rp);
 	else
@@ -1298,7 +1298,7 @@ static int register_probe_event(struct trace_probe *tp)
 	call->id = register_ftrace_event(&tp->event);
 	if (!call->id)
 		return -ENODEV;
-	call->enabled = 1;
+	call->enabled = 0;
 	call->regfunc = probe_event_enable;
 	call->unregfunc = probe_event_disable;
 


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com
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