linux-kernel - [PATCH 3/3] tracing: Add 2 new funcs. for kernel access to Ftrace instances.

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Date:   Tue,  4 Jun 2019 17:42:05 -0700
From:   Divya Indi <divya.indi@...cle.com>
To:     linux-kernel@...r.kernel.org
Cc:     Srinivas Eeda <srinivas.eeda@...cle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Divya Indi <divya.indi@...cle.com>
Subject: [PATCH 3/3] tracing: Add 2 new funcs. for kernel access to Ftrace instances.

Adding 2 new functions -
1) trace_array_lookup : Look up and return a trace array, given its
name.
2) trace_array_set_clr_event : Enable/disable event recording to the
given trace array.

Signed-off-by: Divya Indi <divya.indi@...cle.com>
---
 include/linux/trace_events.h |  3 +++
 kernel/trace/trace.c         | 11 +++++++++++
 kernel/trace/trace_events.c  | 22 ++++++++++++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index d7b7d85..0cc99a8 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -545,7 +545,10 @@ int trace_array_printk(struct trace_array *tr, unsigned long ip,
 struct trace_array *trace_array_create(const char *name);
 int trace_array_destroy(struct trace_array *tr);
 int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set);
+struct trace_array *trace_array_lookup(const char *name);
 int trace_set_clr_event(const char *system, const char *event, int set);
+int trace_array_set_clr_event(struct trace_array *tr, const char *system,
+		const char *event, int set);
 
 /*
  * The double __builtin_constant_p is because gcc will give us an error
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a60dc13..1d171fd 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8465,6 +8465,17 @@ static int instance_rmdir(const char *name)
 	return ret;
 }
 
+struct trace_array *trace_array_lookup(const char *name)
+{
+	struct trace_array *tr;
+	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+		if (tr->name && strcmp(tr->name, name) == 0)
+			return tr;
+	}
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(trace_array_lookup);
+
 static __init void create_trace_instances(struct dentry *d_tracer)
 {
 	trace_instance_dir = tracefs_create_instance_dir("instances", d_tracer,
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 445b059..c126d2c 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -859,6 +859,28 @@ int trace_set_clr_event(const char *system, const char *event, int set)
 }
 EXPORT_SYMBOL_GPL(trace_set_clr_event);
 
+/**
+ * trace_array_set_clr_event - enable or disable an event for a trace array
+ * @system: system name to match (NULL for any system)
+ * @event: event name to match (NULL for all events, within system)
+ * @set: 1 to enable, 0 to disable
+ *
+ * This is a way for other parts of the kernel to enable or disable
+ * event recording to instances.
+ *
+ * Returns 0 on success, -EINVAL if the parameters do not match any
+ * registered events.
+ */
+int trace_array_set_clr_event(struct trace_array *tr, const char *system,
+		const char *event, int set)
+{
+	if (!tr)
+		return -ENODEV;
+
+	return __ftrace_set_clr_event(tr, NULL, system, event, set);
+}
+EXPORT_SYMBOL_GPL(trace_array_set_clr_event);
+
 /* 128 should be much more than enough */
 #define EVENT_BUF_SIZE		127
 
-- 
1.8.3.1