[PATCH] tracing: Report wrong dynamic event command

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Report wrong dynamic event command via error_log.
---
 # echo "z hoge" > /sys/kernel/tracing/dynamic_events
 sh: write error: Invalid argument
 # cat /sys/kernel/tracing/error_log
 [   73.371714] dynevent: error: Invalid dynamic event command
  Command: z hoge
           ^
---

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 kernel/trace/trace_dynevent.c |   11 +++++++++--
 kernel/trace/trace_probe.h    |    3 ++-
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_dynevent.c b/kernel/trace/trace_dynevent.c
index d06854bd32b3..536a7704abfd 100644
--- a/kernel/trace/trace_dynevent.c
+++ b/kernel/trace/trace_dynevent.c
@@ -14,6 +14,7 @@
 
 #include "trace.h"
 #include "trace_output.h"	/* for trace_event_sem */
+#include "trace_probe.h"
 #include "trace_dynevent.h"
 
 DEFINE_MUTEX(dyn_event_ops_mutex);
@@ -144,9 +145,15 @@ static int create_dyn_event(const char *raw_command)
 		if (!ret || ret != -ECANCELED)
 			break;
 	}
-	mutex_unlock(&dyn_event_ops_mutex);
-	if (ret == -ECANCELED)
+	if (ret == -ECANCELED) {
+		/* Wrong dynamic event. Leave an error message. */
+		trace_probe_log_init("dynevent", 1, &raw_command);
+		trace_probe_log_err(0, BAD_DYN_EVENT);
+		trace_probe_log_clear();
 		ret = -EINVAL;
+	}
+
+	mutex_unlock(&dyn_event_ops_mutex);
 
 	return ret;
 }
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 591adc9bb1e9..e6e5c884e60a 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -567,7 +567,8 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 	C(BAD_ACCESS_FMT,	"Access memory address requires @"),	\
 	C(BAD_ACCESS_TYPE,	"Bad memory access type"),	\
 	C(BAD_ACCESS_LEN,	"This memory access length is not supported"), \
-	C(BAD_ACCESS_ADDR,	"Invalid access memory address"),
+	C(BAD_ACCESS_ADDR,	"Invalid access memory address"),	\
+	C(BAD_DYN_EVENT,	"Invalid dynamic event command"),
 
 #undef C
 #define C(a, b)		TP_ERR_##a