[RFC PATCH v3 12/19] tracing/boot: Add per-event settings

[Masami Hiramatsu <mhiramat@xxxxxxxxxx>]

Add per-event settings for boottime tracing. User can set filter,
actions and enable on each event on boot. The event entries are
under ftrace.event.GROUP.EVENT node (note that the option key
includes event's group name and event name.) This supports below
commands.

 - ftrace.event.GROUP.EVENT.enable;
   Enables GROUP:EVENT tracing.

 - ftrace.event.GROUP.EVENT.filter = FILTER;
   Set FILTER rule to the GROUP:EVENT.

 - ftrace.event.GROUP.EVENT.actions = ACTION[, ACTION2...];
   Set ACTIONs to the GROUP:EVENT.

For example,

  ftrace.event.sched.sched_process_exec {
                filter = "pid < 128";
		enable;
  }

this will enable tracing "sched:sched_process_exec" event
with "pid < 128" filter.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
 kernel/trace/trace_boot.c           |   60 +++++++++++++++++++++++++++++++++++
 kernel/trace/trace_events_trigger.c |    2 +
 2 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index cc5e81368065..cfd628c16761 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -80,6 +80,7 @@ trace_boot_set_ftrace_options(struct trace_array *tr, struct skc_node *node)
 
 #ifdef CONFIG_EVENT_TRACING
 extern int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set);
+extern int trigger_process_regex(struct trace_event_file *file, char *buff);
 
 static void __init
 trace_boot_enable_events(struct trace_array *tr, struct skc_node *node)
@@ -98,8 +99,66 @@ trace_boot_enable_events(struct trace_array *tr, struct skc_node *node)
 			pr_err("Failed to enable event: %s\n", p);
 	}
 }
+
+static void __init
+trace_boot_init_one_event(struct trace_array *tr, struct skc_node *gnode,
+			  struct skc_node *enode)
+{
+	struct trace_event_file *file;
+	struct skc_node *anode;
+	char buf[MAX_BUF_LEN];
+	const char *p, *group, *event;
+
+	group = skc_node_get_data(gnode);
+	event = skc_node_get_data(enode);
+
+	mutex_lock(&event_mutex);
+	file = find_event_file(tr, group, event);
+	if (!file) {
+		pr_err("Failed to find event: %s:%s\n", group, event);
+		goto out;
+	}
+
+	p = skc_node_find_value(enode, "filter", NULL);
+	if (p && *p != '\0') {
+		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
+			pr_err("filter string is too long: %s\n", p);
+		else if (apply_event_filter(file, buf) < 0)
+			pr_err("Failed to apply filter: %s\n", buf);
+	}
+
+	skc_node_for_each_array_value(enode, "actions", anode, p) {
+		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
+			pr_err("action string is too long: %s\n", p);
+		else if (trigger_process_regex(file, buf) < 0)
+			pr_err("Failed to apply an action: %s\n", buf);
+	}
+
+	if (skc_node_find_value(enode, "enable", NULL)) {
+		if (trace_event_enable_disable(file, 1, 0) < 0)
+			pr_err("Failed to enable event node: %s:%s\n",
+				group, event);
+	}
+out:
+	mutex_unlock(&event_mutex);
+}
+
+static void __init
+trace_boot_init_events(struct trace_array *tr, struct skc_node *node)
+{
+	struct skc_node *gnode, *enode;
+
+	node = skc_node_find_child(node, "event");
+	if (!node)
+		return;
+	/* per-event key starts with "event.GROUP.EVENT" */
+	skc_node_for_each_child(node, gnode)
+		skc_node_for_each_child(gnode, enode)
+			trace_boot_init_one_event(tr, gnode, enode);
+}
 #else
 #define trace_boot_enable_events(tr, node) do {} while (0)
+#define trace_boot_init_events(tr, node) do {} while (0)
 #endif
 
 static void __init
@@ -128,6 +187,7 @@ static int __init trace_boot_init(void)
 		return 0;
 
 	trace_boot_set_ftrace_options(tr, trace_node);
+	trace_boot_init_events(tr, trace_node);
 	trace_boot_enable_events(tr, trace_node);
 	trace_boot_enable_tracer(tr, trace_node);
 
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 2a2912cb4533..74a19c18219f 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -208,7 +208,7 @@ static int event_trigger_regex_open(struct inode *inode, struct file *file)
 	return ret;
 }
 
-static int trigger_process_regex(struct trace_event_file *file, char *buff)
+int trigger_process_regex(struct trace_event_file *file, char *buff)
 {
 	char *command, *next = buff;
 	struct event_command *p;