linux-kernel - [PATCH v2 1/4] perf/trace: Add function to find event type by name

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Date:	Tue, 8 Sep 2015 14:49:21 +0900
From:	Takao Indoh <indou.takao@...fujitsu.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>
CC:	<linux-kernel@...r.kernel.org>, <x86@...nel.org>
Subject: [PATCH v2 1/4] perf/trace: Add function to find event type by name

This patch adds function to find struct trace_event by event name like
"sched_switch" , and return its type so that Intel PT logger can enable
the trace event in kernel. Intel PT logger needs this because it needs
sched_switch tracing to collect side-band data.

Signed-off-by: Takao Indoh <indou.takao@...fujitsu.com>
---
 include/linux/trace_events.h    |    2 ++
 kernel/trace/trace_event_perf.c |   22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index ed27917..d3cae4b 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -616,6 +616,8 @@ perf_trace_buf_submit(void *raw_data, int size, int rctx, u64 addr,
 {
 	perf_tp_event(addr, count, raw_data, size, regs, head, rctx, task);
 }
+
+int perf_trace_event_get_type_by_name(char *system, char *name);
 #endif
 
 #endif /* _LINUX_TRACE_EVENT_H */
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index abfc903..1a851d5 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -21,6 +21,28 @@ typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
 /* Count the events in use (per event id, not per instance) */
 static int	total_ref_count;
 
+int perf_trace_event_get_type_by_name(char *system, char *name)
+{
+	struct trace_event_call *tp_event;
+	int ret = 0;
+	/*
+	 * All type is larger than __TRACE_LAST_TYPE + 1. Therefore return zero
+	 * as a invalid type if not found.
+	 */
+
+	mutex_lock(&event_mutex);
+	list_for_each_entry(tp_event, &ftrace_events, list) {
+		if (!strcmp(tp_event->class->system, system) &&
+		    !strcmp(trace_event_name(tp_event), name)) {
+			ret = tp_event->event.type;
+			break;
+		}
+	}
+	mutex_unlock(&event_mutex);
+
+	return ret;
+}
+
 static int perf_trace_event_perm(struct trace_event_call *tp_event,
 				 struct perf_event *p_event)
 {
-- 
1.7.1


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