tracing/eprobe: Show syntax error logs in error_log file

Show the syntax errors for event probes in error_log file as same as
other dynamic events, so that user can understand what is the problem.

Link: https://lkml.kernel.org/r/165932113556.2850673.3483079297896607612.stgit@devnote2

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

Author: mhiramat

kernel/trace/trace_eprobe.c

@@ -839,8 +839,11 @@ static int trace_eprobe_tp_update_arg(struct trace_eprobe *ep, const char *argv[
 	if (ret)
 		return ret;
 
-	if (ep->tp.args[i].code->op == FETCH_OP_TP_ARG)
+	if (ep->tp.args[i].code->op == FETCH_OP_TP_ARG) {
 		ret = trace_eprobe_tp_arg_update(ep, i);
+		if (ret)
+			trace_probe_log_err(0, BAD_ATTACH_ARG);
+	}
 
 	return ret;
 }
@@ -880,8 +883,10 @@ static int __trace_eprobe_create(int argc, const char *argv[])
 	trace_probe_log_set_index(1);
 	sys_event = argv[1];
 	ret = traceprobe_parse_event_name(&sys_event, &sys_name, buf2, 0);
-	if (!sys_event || !sys_name)
+	if (!sys_event || !sys_name) {
+		trace_probe_log_err(0, NO_EVENT_INFO);
 		goto parse_error;
+	}
 
 	if (!event) {
 		strscpy(buf1, argv[1], MAX_EVENT_NAME_LEN);
@@ -896,6 +901,8 @@ static int __trace_eprobe_create(int argc, const char *argv[])
 
 	if (IS_ERR(ep)) {
 		ret = PTR_ERR(ep);
+		if (ret == -ENODEV)
+			trace_probe_log_err(0, BAD_ATTACH_EVENT);
 		/* This must return -ENOMEM or missing event, else there is a bug */
 		WARN_ON_ONCE(ret != -ENOMEM && ret != -ENODEV);
 		ep = NULL;

kernel/trace/trace_probe.h

@@ -442,7 +442,10 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 	C(FAIL_REG_PROBE,	"Failed to register probe event"),\
 	C(DIFF_PROBE_TYPE,	"Probe type is different from existing probe"),\
 	C(DIFF_ARG_TYPE,	"Argument type or name is different from existing probe"),\
-	C(SAME_PROBE,		"There is already the exact same probe event"),
+	C(SAME_PROBE,		"There is already the exact same probe event"),\
+	C(NO_EVENT_INFO,	"This requires both group and event name to attach"),\
+	C(BAD_ATTACH_EVENT,	"Attached event does not exist"),\
+	C(BAD_ATTACH_ARG,	"Attached event does not have this field"),
 
 #undef C
 #define C(a, b)		TP_ERR_##a