linux-kernel - [PATCH 23/24] tracing/kprobes: Disable kprobe events by default after creation

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Date:	Tue, 22 Sep 2009 21:38:21 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Li Zefan <lizf@...fujitsu.com>,
	Jim Keniston <jkenisto@...ibm.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>,
	Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Tom Zanussi <tzanussi@...il.com>
Subject: [PATCH 23/24] tracing/kprobes: Disable kprobe events by default after creation

From: Masami Hiramatsu <mhiramat@...hat.com>

Disable newly created kprobe events by default, not to disturb
another user using ftrace. "Disturb" means when someone is 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. Fix this to allow proper
and transparent kprobes events concurrent usage between ftrace
users and perf users.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Acked-by: Steven Rostedt <rostedt@...dmis.org>
Cc: 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: Tom Zanussi <tzanussi@...il.com>
LKML-Reference: <20090914204937.18779.59422.stgit@...p-100-2-132.bos.redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...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;
 
-- 
1.6.2.3

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