[PATCH v4 26/37] tracing: Add 'onmatch' hist trigger action support

[Tom Zanussi]

Add an 'onmatch(matching.event).<synthetic_event_name>(param list)'
hist trigger action which is invoked with the set of variables or
event fields named in the 'param list'.  The result is the generation
of a synthetic event that consists of the values contained in those
variables and/or fields at the time the invoking event was hit.

As an example the below defines a simple synthetic event using a
variable defined on the sched_wakeup_new event, and shows the event
definition with unresolved fields, since the sched_wakeup_new event
with the testpid variable hasn't been defined yet:

    # echo 'wakeup_new_test pid_t pid; int prio' >> \
      /sys/kernel/debug/tracing/synthetic_events

    # cat /sys/kernel/debug/tracing/synthetic_events
      wakeup_new_test pid_t pid; int prio

The following hist trigger both defines a testpid variable and
specifies an onmatch() trace action that uses that variable along with
a non-variable field to generate a wakeup_new_test synthetic event
whenever a sched_wakeup_new event occurs, which because of the 'if
comm == "cyclictest"' filter only happens when the executable is
cyclictest:

    # echo 'hist:testpid=pid:keys=$testpid:\
      onmatch(sched.sched_wakeup_new).wakeup_new_test($testpid, prio) \
        if comm=="cyclictest"' >> \
      /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger

Creating and displaying a histogram based on those events is now just
a matter of using the fields and new synthetic event in the
tracing/events/synthetic directory, as usual:

    # echo 'hist:keys=pid,prio:sort=pid,prio' >> \
      /sys/kernel/debug/tracing/events/synthetic/wakeup_new_test/trigger

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Signed-off-by: Rajvi Jingar <rajvi.jingar@xxxxxxxxx>
---
 kernel/trace/trace_events_hist.c | 475 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 460 insertions(+), 15 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 906c2a1..8ccebad 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -323,7 +323,18 @@ typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
 
 struct action_data {
 	action_fn_t		fn;
-	unsigned int		var_ref_idx;
+	unsigned int		n_params;
+	char			*params[SYNTH_FIELDS_MAX];
+
+	union {
+		struct {
+			unsigned int		var_ref_idx;
+			char			*match_event;
+			char			*match_event_system;
+			char			*synth_event_name;
+			struct synth_event	*synth_event;
+		} onmatch;
+	};
 };
 
 static LIST_HEAD(synth_event_list);
@@ -889,6 +900,21 @@ static struct synth_event *alloc_synth_event(char *event_name, int n_fields,
 	return event;
 }
 
+static void action_trace(struct hist_trigger_data *hist_data,
+			 struct tracing_map_elt *elt, void *rec,
+			 struct ring_buffer_event *rbe,
+			 struct action_data *data, u64 *var_ref_vals)
+{
+	struct synth_event *event = data->onmatch.synth_event;
+
+	trace_synth(event, var_ref_vals, data->onmatch.var_ref_idx);
+}
+
+struct hist_var_data {
+	struct list_head list;
+	struct hist_trigger_data *hist_data;
+};
+
 static int create_synth_event(int argc, char **argv)
 {
 	struct synth_field *field, *fields[SYNTH_FIELDS_MAX];
@@ -1139,11 +1165,6 @@ static u64 hist_field_timestamp(struct hist_field *hist_field,
 	return ts;
 }
 
-struct hist_var_data {
-	struct list_head list;
-	struct hist_trigger_data *hist_data;
-};
-
 static struct hist_field *
 check_field_for_var_ref(struct hist_field *hist_field,
 			struct hist_trigger_data *var_data,
@@ -1447,6 +1468,37 @@ static struct hist_field *find_file_var(struct trace_event_file *file,
 	return NULL;
 }
 
+static struct hist_field *
+find_match_var(struct hist_trigger_data *hist_data, char *var_name)
+{
+	struct trace_array *tr = hist_data->event_file->tr;
+	struct hist_field *hist_field, *found = NULL;
+	struct trace_event_file *file;
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		struct action_data *data = hist_data->actions[i];
+
+		if (data->fn == action_trace) {
+			char *system = data->onmatch.match_event_system;
+			char *event_name = data->onmatch.match_event;
+
+			file = find_var_file(tr, system, event_name, var_name);
+			if (!file)
+				continue;
+			hist_field = find_file_var(file, var_name);
+			if (hist_field) {
+				if (found) {
+					return ERR_PTR(-EINVAL);
+				}
+
+				found = hist_field;
+			}
+		}
+	}
+	return found;
+}
+
 static struct hist_field *find_event_var(struct hist_trigger_data *hist_data,
 					 char *system,
 					 char *event_name,
@@ -1456,6 +1508,14 @@ static struct hist_field *find_event_var(struct hist_trigger_data *hist_data,
 	struct hist_field *hist_field = NULL;
 	struct trace_event_file *file;
 
+	if (!system || !event_name) {
+		hist_field = find_match_var(hist_data, var_name);
+		if (IS_ERR(hist_field))
+			return NULL;
+		if (hist_field)
+			return hist_field;
+	}
+
 	file = find_var_file(tr, system, event_name, var_name);
 	if (!file)
 		return NULL;
@@ -1647,11 +1707,21 @@ static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
 
 static int parse_action(char *str, struct hist_trigger_attrs *attrs)
 {
-	int ret = 0;
+	int ret = -EINVAL;
 
 	if (attrs->n_actions >= HIST_ACTIONS_MAX)
 		return ret;
 
+	if ((strncmp(str, "onmatch(", strlen("onmatch(")) == 0)) {
+		attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
+		if (!attrs->action_str[attrs->n_actions]) {
+			ret = -ENOMEM;
+			return ret;
+		}
+		attrs->n_actions++;
+		ret = 0;
+	}
+
 	return ret;
 }
 
@@ -2596,7 +2666,6 @@ static struct trace_event_file *event_file(struct trace_array *tr,
 find_synthetic_field_var(struct hist_trigger_data *target_hist_data,
 			 char *system, char *event_name, char *field_name)
 {
-	struct trace_array *tr = target_hist_data->event_file->tr;
 	struct hist_field *event_var;
 	char *synthetic_name;
 
@@ -2607,7 +2676,7 @@ static struct trace_event_file *event_file(struct trace_array *tr,
 	strcpy(synthetic_name, "synthetic_");
 	strcat(synthetic_name, field_name);
 
-	event_var = find_event_var(tr, system, event_name, synthetic_name);
+	event_var = find_event_var(target_hist_data, system, event_name, synthetic_name);
 
 	kfree(synthetic_name);
 
@@ -2639,7 +2708,7 @@ static struct trace_event_file *event_file(struct trace_array *tr,
  *
  * Return: The variable created for the field.
  */
-struct hist_field *
+static struct hist_field *
 create_field_var_hist(struct hist_trigger_data *target_hist_data,
 		      char *subsys_name, char *event_name, char *field_name)
 {
@@ -2753,7 +2822,7 @@ struct hist_field *
 	return event_var;
 }
 
-struct hist_field *
+static struct hist_field *
 find_target_event_var(struct hist_trigger_data *hist_data,
 		      char *subsys_name, char *event_name, char *var_name)
 {
@@ -2924,7 +2993,7 @@ static struct field_var *create_field_var(struct hist_trigger_data *hist_data,
  *
  * Return: The variable created for the field.
  */
-struct field_var *
+static struct field_var *
 create_target_field_var(struct hist_trigger_data *target_hist_data,
 			char *subsys_name, char *event_name, char *var_name)
 {
@@ -2948,6 +3017,27 @@ struct field_var *
 	return create_field_var(target_hist_data, file, var_name);
 }
 
+static void onmatch_destroy(struct action_data *data)
+{
+	unsigned int i;
+
+	mutex_lock(&synth_event_mutex);
+
+	kfree(data->onmatch.match_event);
+	kfree(data->onmatch.match_event_system);
+	kfree(data->onmatch.synth_event_name);
+
+	for (i = 0; i < data->n_params; i++)
+		kfree(data->params[i]);
+
+	if (data->onmatch.synth_event)
+		data->onmatch.synth_event->ref--;
+
+	kfree(data);
+
+	mutex_unlock(&synth_event_mutex);
+}
+
 static void destroy_field_var(struct field_var *field_var)
 {
 	if (!field_var)
@@ -2967,8 +3057,8 @@ static void destroy_field_vars(struct hist_trigger_data *hist_data)
 		destroy_field_var(hist_data->field_vars[i]);
 }
 
-void save_field_var(struct hist_trigger_data *hist_data,
-		    struct field_var *field_var)
+static void save_field_var(struct hist_trigger_data *hist_data,
+			   struct field_var *field_var)
 {
 	hist_data->field_vars[hist_data->n_field_vars++] = field_var;
 
@@ -2976,6 +3066,298 @@ void save_field_var(struct hist_trigger_data *hist_data,
 		hist_data->n_field_var_str++;
 }
 
+
+static void destroy_synth_var_refs(struct hist_trigger_data *hist_data)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_synth_var_refs; i++)
+		destroy_hist_field(hist_data->synth_var_refs[i], 0);
+}
+
+static void save_synth_var_ref(struct hist_trigger_data *hist_data,
+			 struct hist_field *var_ref)
+{
+	hist_data->synth_var_refs[hist_data->n_synth_var_refs++] = var_ref;
+
+	hist_data->var_refs[hist_data->n_var_refs] = var_ref;
+	var_ref->var_ref_idx = hist_data->n_var_refs++;
+}
+
+static int check_synth_field(struct synth_event *event,
+			     struct hist_field *hist_field,
+			     unsigned int field_pos)
+{
+	struct synth_field *field;
+
+	if (field_pos >= event->n_fields)
+		return -EINVAL;
+
+	field = event->fields[field_pos];
+
+	if (strcmp(field->type, hist_field->type) != 0)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int parse_action_params(char *params, struct action_data *data)
+{
+	char *param, *saved_param;
+	int ret = 0;
+
+	while (params) {
+		if (data->n_params >= SYNTH_FIELDS_MAX)
+			goto out;
+
+		param = strsep(&params, ",");
+		if (!param) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		param = strstrip(param);
+		if (strlen(param) < 2) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		saved_param = kstrdup(param, GFP_KERNEL);
+		if (!saved_param) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		data->params[data->n_params++] = saved_param;
+	}
+ out:
+	return ret;
+}
+
+static struct hist_field *
+onmatch_find_var(struct hist_trigger_data *hist_data, struct action_data *data,
+		 char *system, char *event, char *var)
+{
+	struct hist_field *hist_field;
+
+	var++; /* skip '$' */
+
+	hist_field = find_target_event_var(hist_data, system, event, var);
+	if (!hist_field) {
+		if (!system) {
+			system = data->onmatch.match_event_system;
+			event = data->onmatch.match_event;
+		}
+
+		hist_field = find_event_var(hist_data, system, event, var);
+	}
+
+	return hist_field;
+}
+
+static struct hist_field *
+onmatch_create_field_var(struct hist_trigger_data *hist_data,
+			 struct action_data *data, char *system,
+			 char *event, char *var)
+{
+	struct hist_field *hist_field = NULL;
+	struct field_var *field_var;
+
+	/*
+	 * First try to create a field var on the target event (the
+	 * currently being defined).  This will create a variable for
+	 * unqualified fields on the target event, or if qualified,
+	 * target fields that have qualified names matching the target.
+	 */
+	field_var = create_target_field_var(hist_data, system, event, var);
+
+	if (field_var && !IS_ERR(field_var)) {
+		save_field_var(hist_data, field_var);
+		hist_field = field_var->var;
+	} else {
+		field_var = NULL;
+		/*
+		 * If no explicit system.event is specfied, default to
+		 * looking for fields on the onmatch(system.event.xxx)
+		 * event.
+		 */
+		if (!system) {
+			system = data->onmatch.match_event_system;
+			event = data->onmatch.match_event;
+		}
+
+		/*
+		 * At this point, we're looking at a field on another
+		 * event.  Because we can't modify a hist trigger on
+		 * another event to add a variable for a field, we need
+		 * to create a new trigger on that event and create the
+		 * variable at the same time.
+		 */
+		hist_field = create_field_var_hist(hist_data, system, event, var);
+		if (IS_ERR(hist_field))
+			goto free;
+	}
+ out:
+	return hist_field;
+ free:
+	destroy_field_var(field_var);
+	hist_field = NULL;
+	goto out;
+}
+
+static int onmatch_create(struct hist_trigger_data *hist_data,
+			  struct trace_event_file *file,
+			  struct action_data *data)
+{
+	char *event_name, *param, *system = NULL;
+	struct hist_field *hist_field, *var_ref;
+	unsigned int i, var_ref_idx;
+	unsigned int field_pos = 0;
+	struct synth_event *event;
+	int ret = 0;
+
+	mutex_lock(&synth_event_mutex);
+	event = find_synth_event(data->onmatch.synth_event_name);
+	if (!event) {
+		mutex_unlock(&synth_event_mutex);
+		return -EINVAL;
+	}
+	mutex_unlock(&synth_event_mutex);
+
+	var_ref_idx = hist_data->n_var_refs;
+
+	for (i = 0; i < data->n_params; i++) {
+		char *p;
+
+		p = param = kstrdup(data->params[i], GFP_KERNEL);
+		if (!param) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		system = strsep(&param, ".");
+		if (!param) {
+			param = (char *)system;
+			system = event_name = NULL;
+		} else {
+			event_name = strsep(&param, ".");
+			if (!param) {
+				kfree(p);
+				ret = -EINVAL;
+				goto out;
+			}
+		}
+
+		if (param[0] == '$')
+			hist_field = onmatch_find_var(hist_data, data, system,
+						      event_name, param);
+		else
+			hist_field = onmatch_create_field_var(hist_data, data,
+							      system,
+							      event_name,
+							      param);
+
+		if (!hist_field) {
+			kfree(p);
+			ret = -EINVAL;
+			goto out;
+		}
+
+		if (check_synth_field(event, hist_field, field_pos) == 0) {
+			var_ref = create_var_ref(hist_field, system, event_name);
+			if (!var_ref) {
+				kfree(p);
+				ret = -ENOMEM;
+				goto out;
+			}
+
+			save_synth_var_ref(hist_data, var_ref);
+			field_pos++;
+			kfree(p);
+			continue;
+		}
+
+		kfree(p);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (field_pos != event->n_fields) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	data->fn = action_trace;
+	data->onmatch.synth_event = event;
+	data->onmatch.var_ref_idx = var_ref_idx;
+	event->ref++;
+ out:
+	return ret;
+}
+
+static struct action_data *onmatch_parse(struct trace_array *tr, char *str)
+{
+	char *match_event, *match_event_system;
+	char *synth_event_name, *params;
+	struct action_data *data;
+	int ret = -EINVAL;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return ERR_PTR(-ENOMEM);
+
+	match_event = strsep(&str, ")");
+	if (!match_event || !str)
+		goto free;
+
+	match_event_system = strsep(&match_event, ".");
+	if (!match_event)
+		goto free;
+
+	if (IS_ERR(event_file(tr, match_event_system, match_event)))
+		goto free;
+
+	data->onmatch.match_event = kstrdup(match_event, GFP_KERNEL);
+	if (!data->onmatch.match_event) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	data->onmatch.match_event_system = kstrdup(match_event_system, GFP_KERNEL);
+	if (!data->onmatch.match_event_system) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	strsep(&str, ".");
+	if (!str)
+		goto free;
+
+	synth_event_name = strsep(&str, "(");
+	if (!synth_event_name || !str)
+		goto free;
+
+	data->onmatch.synth_event_name = kstrdup(synth_event_name, GFP_KERNEL);
+	if (!data->onmatch.synth_event_name) {
+		ret = -ENOMEM;
+		goto free;
+	}
+
+	params = strsep(&str, ")");
+	if (!params || !str || (str && strlen(str)))
+		goto free;
+
+	ret = parse_action_params(params, data);
+	if (ret)
+		goto free;
+ out:
+	return data;
+ free:
+	onmatch_destroy(data);
+	data = ERR_PTR(ret);
+	goto out;
+}
+
 static int create_hitcount_val(struct hist_trigger_data *hist_data)
 {
 	hist_data->fields[HITCOUNT_IDX] =
@@ -3400,18 +3782,39 @@ static void destroy_actions(struct hist_trigger_data *hist_data)
 	for (i = 0; i < hist_data->n_actions; i++) {
 		struct action_data *data = hist_data->actions[i];
 
-		kfree(data);
+		if (data->fn == action_trace)
+			onmatch_destroy(data);
+		else
+			kfree(data);
 	}
 }
 
 static int parse_actions(struct hist_trigger_data *hist_data)
 {
+	struct trace_array *tr = hist_data->event_file->tr;
+	struct action_data *data;
 	unsigned int i;
 	int ret = 0;
 	char *str;
 
 	for (i = 0; i < hist_data->attrs->n_actions; i++) {
 		str = hist_data->attrs->action_str[i];
+
+		if (strncmp(str, "onmatch(", strlen("onmatch(")) == 0) {
+			char *action_str = str + strlen("onmatch(");
+
+			data = onmatch_parse(tr, action_str);
+			if (IS_ERR(data)) {
+				ret = PTR_ERR(data);
+				break;
+			}
+			data->fn = action_trace;
+		} else {
+			ret = -EINVAL;
+			break;
+		}
+
+		hist_data->actions[hist_data->n_actions++] = data;
 	}
 
 	return ret;
@@ -3426,11 +3829,50 @@ static int create_actions(struct hist_trigger_data *hist_data,
 
 	for (i = 0; i < hist_data->attrs->n_actions; i++) {
 		data = hist_data->actions[i];
+
+		if (data->fn == action_trace) {
+			ret = onmatch_create(hist_data, file, data);
+			if (ret)
+				return ret;
+		}
 	}
 
 	return ret;
 }
 
+static void print_onmatch_spec(struct seq_file *m,
+			       struct hist_trigger_data *hist_data,
+			       struct action_data *data)
+{
+	unsigned int i;
+
+	seq_printf(m, ":onmatch(%s.%s).", data->onmatch.match_event_system,
+		   data->onmatch.match_event);
+
+	seq_printf(m, "%s(", data->onmatch.synth_event->name);
+
+	for (i = 0; i < data->n_params; i++) {
+		if (i)
+			seq_puts(m, ",");
+		seq_printf(m, "%s", data->params[i]);
+	}
+
+	seq_puts(m, ")");
+}
+
+static void print_actions_spec(struct seq_file *m,
+			       struct hist_trigger_data *hist_data)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		struct action_data *data = hist_data->actions[i];
+
+		if (data->fn == action_trace)
+			print_onmatch_spec(m, hist_data, data);
+	}
+}
+
 static void destroy_field_var_hists(struct hist_trigger_data *hist_data)
 {
 	unsigned int i;
@@ -3453,6 +3895,7 @@ static void destroy_hist_data(struct hist_trigger_data *hist_data)
 	destroy_actions(hist_data);
 	destroy_field_vars(hist_data);
 	destroy_field_var_hists(hist_data);
+	destroy_synth_var_refs(hist_data);
 
 	kfree(hist_data);
 }
@@ -4009,6 +4452,8 @@ static int event_hist_trigger_print(struct seq_file *m,
 	}
 	seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
 
+	print_actions_spec(m, hist_data);
+
 	if (data->filter_str)
 		seq_printf(m, " if %s", data->filter_str);
 
-- 
1.9.3