[PATCH v9 26/37] tracing: Add 'onmatch' hist trigger action support

From: Tom Zanussi
Date: Mon Jan 15 2018 - 21:58:14 EST

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 | 488 +++++++++++++++++++++++++++++++++++++--
1 file changed, 475 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index ecb2c9a..67f1f0f 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -285,6 +285,8 @@ struct hist_trigger_data {
struct action_data *actions[HIST_ACTIONS_MAX];
unsigned int n_actions;

+ struct hist_field *synth_var_refs[SYNTH_FIELDS_MAX];
+ unsigned int n_synth_var_refs;
struct field_var *field_vars[SYNTH_FIELDS_MAX];
unsigned int n_field_vars;
unsigned int n_field_var_str;
@@ -321,7 +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);
@@ -887,6 +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 void add_or_delete_synth_event(struct synth_event *event, int delete)
{
if (delete)
@@ -1124,11 +1152,6 @@ 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,
@@ -1194,6 +1217,14 @@ static struct hist_field *find_var_ref(struct hist_trigger_data *hist_data,
return found;
}

+ for (i = 0; i < hist_data->n_synth_var_refs; i++) {
+ hist_field = hist_data->synth_var_refs[i];
+ found = check_field_for_var_refs(hist_data, hist_field,
+ var_data, var_idx, 0);
+ if (found)
+ return found;
+ }
+
return found;
}

@@ -1422,6 +1453,37 @@ 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,
@@ -1431,6 +1493,14 @@ 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;
@@ -1622,11 +1692,21 @@ 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;
}

@@ -2635,7 +2715,7 @@ 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)
{
@@ -2748,7 +2828,7 @@ 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)
{
@@ -2919,7 +2999,7 @@ 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)
{
@@ -2943,6 +3023,27 @@ 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)
@@ -2962,8 +3063,8 @@ 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;

@@ -2971,6 +3072,304 @@ 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;
+ }
+ event->ref++;
+ 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 err;
+ }
+
+ system = strsep(&param, ".");
+ if (!param) {
+ param = (char *)system;
+ system = event_name = NULL;
+ } else {
+ event_name = strsep(&param, ".");
+ if (!param) {
+ kfree(p);
+ ret = -EINVAL;
+ goto err;
+ }
+ }
+
+ 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 err;
+ }
+
+ 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 err;
+ }
+
+ save_synth_var_ref(hist_data, var_ref);
+ field_pos++;
+ kfree(p);
+ continue;
+ }
+
+ kfree(p);
+ ret = -EINVAL;
+ goto err;
+ }
+
+ if (field_pos != event->n_fields) {
+ ret = -EINVAL;
+ goto err;
+ }
+
+ data->fn = action_trace;
+ data->onmatch.synth_event = event;
+ data->onmatch.var_ref_idx = var_ref_idx;
+ out:
+ return ret;
+ err:
+ mutex_lock(&synth_event_mutex);
+ event->ref--;
+ mutex_unlock(&synth_event_mutex);
+
+ goto out;
+}
+
+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] =
@@ -3395,18 +3794,39 @@ 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;
@@ -3421,11 +3841,50 @@ 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;
@@ -3448,6 +3907,7 @@ 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);
}
@@ -4004,6 +4464,8 @@ 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