[RFC PATCH v2 2/5] tracing: Save the last hist command's associated event name

[Tom Zanussi <zanussi@xxxxxxxxxx>]

From: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>

In preparation for making use of the new trace error log, save the
subsystem and event name associated with the last hist command - it
will be passed as the location param in the event_log_err() calls.

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
---
 kernel/trace/trace_events_hist.c | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 4064e355878c..3e8addebc7be 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -536,15 +536,34 @@ static struct track_data *track_data_alloc(unsigned int key_len,
 	return data;
 }
 
-static char last_hist_cmd[MAX_FILTER_STR_VAL];
+static char last_cmd[MAX_FILTER_STR_VAL];
+static char last_cmd_loc[MAX_FILTER_STR_VAL];
+
 static char hist_err_str[MAX_FILTER_STR_VAL];
 
-static void last_cmd_set(char *str)
+static void last_cmd_set(struct trace_event_file *file, char *str)
 {
+	const char *system = NULL, *name = NULL;
+	struct trace_event_call *call;
+
 	if (!str)
 		return;
 
-	strncpy(last_hist_cmd, str, MAX_FILTER_STR_VAL - 1);
+	strncpy(last_cmd, str, MAX_FILTER_STR_VAL - 1);
+
+	if (file) {
+		call = file->event_call;
+
+		system = call->class->system;
+		if (system) {
+			name = trace_event_name(call);
+			if (!name)
+				system = NULL;
+		}
+	}
+
+	if (system)
+		snprintf(last_cmd_loc, MAX_FILTER_STR_VAL, "hist:%s:%s", system, name);
 }
 
 static void hist_err(char *str, char *var)
@@ -584,6 +603,8 @@ static void hist_err_event(char *str, char *system, char *event, char *var)
 static void hist_err_clear(void)
 {
 	hist_err_str[0] = '\0';
+	last_cmd[0] = '\0';
+	last_cmd_loc[0] = '\0';
 }
 
 static bool have_hist_err(void)
@@ -5440,8 +5461,8 @@ static int hist_show(struct seq_file *m, void *v)
 	}
 
 	if (have_hist_err()) {
-		seq_printf(m, "\nERROR: %s\n", hist_err_str);
-		seq_printf(m, "  Last command: %s\n", last_hist_cmd);
+		seq_printf(m, "\n%s: error: \n", hist_err_str);
+		seq_printf(m, "  Last command: %s\n", last_cmd);
 	}
 
  out_unlock:
@@ -6045,8 +6066,8 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
 	lockdep_assert_held(&event_mutex);
 
 	if (glob && strlen(glob)) {
-		last_cmd_set(param);
 		hist_err_clear();
+		last_cmd_set(file, param);
 	}
 
 	if (!param)
-- 
2.14.1