tracing/boot Add kprobe event support

Add kprobe event support on event node to boot-time tracing.
If the group name of event is "kprobes", the boot-time tracing
defines new probe event according to "probes" values.

 - ftrace.event.kprobes.EVENT.probes = PROBE[, PROBE2...]
   Defines new kprobe event based on PROBEs. It is able to define
   multiple probes on one event, but those must have same type of
   arguments.

For example,

 ftrace.events.kprobes.myevent {
	probes = "vfs_read $arg1 $arg2";
	enable;
 }

This will add kprobes:myevent on vfs_read with the 1st and the 2nd
arguments.

Link: http://lkml.kernel.org/r/157867240104.17873.9712052065426433111.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_boot.c

@@ -76,6 +76,48 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node)
 	}
 }
 
+#ifdef CONFIG_KPROBE_EVENTS
+extern int trace_kprobe_run_command(const char *command);
+
+static int __init
+trace_boot_add_kprobe_event(struct xbc_node *node, const char *event)
+{
+	struct xbc_node *anode;
+	char buf[MAX_BUF_LEN];
+	const char *val;
+	char *p;
+	int len;
+
+	len = snprintf(buf, ARRAY_SIZE(buf) - 1, "p:kprobes/%s ", event);
+	if (len >= ARRAY_SIZE(buf)) {
+		pr_err("Event name is too long: %s\n", event);
+		return -E2BIG;
+	}
+	p = buf + len;
+	len = ARRAY_SIZE(buf) - len;
+
+	xbc_node_for_each_array_value(node, "probes", anode, val) {
+		if (strlcpy(p, val, len) >= len) {
+			pr_err("Probe definition is too long: %s\n", val);
+			return -E2BIG;
+		}
+		if (trace_kprobe_run_command(buf) < 0) {
+			pr_err("Failed to add probe: %s\n", buf);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+#else
+static inline int __init
+trace_boot_add_kprobe_event(struct xbc_node *node, const char *event)
+{
+	pr_err("Kprobe event is not supported.\n");
+	return -ENOTSUPP;
+}
+#endif
+
 static void __init
 trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
 			  struct xbc_node *enode)
@@ -88,6 +130,10 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
 	group = xbc_node_get_data(gnode);
 	event = xbc_node_get_data(enode);
 
+	if (!strcmp(group, "kprobes"))
+		if (trace_boot_add_kprobe_event(enode, event) < 0)
+			return;
+
 	mutex_lock(&event_mutex);
 	file = find_event_file(tr, group, event);
 	if (!file) {

kernel/trace/trace_kprobe.c

@@ -902,6 +902,11 @@ static int create_or_delete_trace_kprobe(int argc, char **argv)
 	return ret == -ECANCELED ? -EINVAL : ret;
 }
 
+int trace_kprobe_run_command(const char *command)
+{
+	return trace_run_command(command, create_or_delete_trace_kprobe);
+}
+
 static int trace_kprobe_release(struct dyn_event *ev)
 {
 	struct trace_kprobe *tk = to_trace_kprobe(ev);