[PATCH v10 17/26] tracing: Add hist trigger 'execname' modifier

[Tom Zanussi <tom.zanussi@linux.intel.com>]

Allow users to have pid fields displayed as program names in the output
by appending '.execname' to field names:

   # echo hist:keys=aaa.execname ... \
              [ if filter] > event/trigger

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
 kernel/trace/trace.c             |  3 +-
 kernel/trace/trace_events_hist.c | 86 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 87 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 12b5907..ac5454e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3811,7 +3811,8 @@ static const char readme_msg[] =
 	"\t    following modifiers to the field name, as applicable:\n\n"
 	"\t            .hex        display a number as a hex value\n"
 	"\t            .sym        display an address as a symbol\n"
-	"\t            .sym-offset display an address as a symbol and offset\n\n"
+	"\t            .sym-offset display an address as a symbol and offset\n"
+	"\t            .execname   display a common_pid as a program name\n\n"
 	"\t    The 'pause' parameter can be used to pause an existing hist\n"
 	"\t    trigger or to start a hist trigger but not log any events\n"
 	"\t    until told to do so.  'continue' can be used to start or\n"
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index e6e5c6e..656973a 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -75,6 +75,7 @@ enum hist_field_flags {
 	HIST_FIELD_HEX		= 8,
 	HIST_FIELD_SYM		= 16,
 	HIST_FIELD_SYM_OFFSET	= 32,
+	HIST_FIELD_EXECNAME	= 64,
 };
 
 struct hist_trigger_attrs {
@@ -218,6 +219,78 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
 	return ERR_PTR(ret);
 }
 
+static inline void save_comm(char *comm, struct task_struct *task)
+{
+	if (!task->pid) {
+		strcpy(comm, "<idle>");
+		return;
+	}
+
+	if (WARN_ON_ONCE(task->pid < 0)) {
+		strcpy(comm, "<XXX>");
+		return;
+	}
+
+	if (task->pid > PID_MAX_DEFAULT) {
+		strcpy(comm, "<...>");
+		return;
+	}
+
+	memcpy(comm, task->comm, TASK_COMM_LEN);
+}
+
+static void hist_trigger_elt_free(struct tracing_map_elt *elt)
+{
+	kfree((char *)elt->private_data);
+}
+
+static int hist_trigger_elt_alloc(struct tracing_map_elt *elt)
+{
+	struct hist_trigger_data *hist_data = elt->map->private_data;
+	struct hist_field *key_field;
+	unsigned int i;
+
+	for (i = hist_data->n_vals; i < hist_data->n_fields; i++) {
+		key_field = hist_data->fields[i];
+
+		if (key_field->flags & HIST_FIELD_EXECNAME) {
+			unsigned int size = TASK_COMM_LEN + 1;
+
+			elt->private_data = kzalloc(size, GFP_KERNEL);
+			if (!elt->private_data)
+				return -ENOMEM;
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static void hist_trigger_elt_copy(struct tracing_map_elt *to,
+				  struct tracing_map_elt *from)
+{
+	char *comm_from = from->private_data;
+	char *comm_to = to->private_data;
+
+	if (comm_from)
+		memcpy(comm_to, comm_from, TASK_COMM_LEN + 1);
+}
+
+static void hist_trigger_elt_init(struct tracing_map_elt *elt)
+{
+	char *comm = elt->private_data;
+
+	if (comm)
+		save_comm(comm, current);
+}
+
+static struct tracing_map_ops hist_trigger_ops = {
+	.elt_alloc	= hist_trigger_elt_alloc,
+	.elt_copy	= hist_trigger_elt_copy,
+	.elt_free	= hist_trigger_elt_free,
+	.elt_init	= hist_trigger_elt_init,
+};
+
 static void destroy_hist_field(struct hist_field *hist_field)
 {
 	kfree(hist_field);
@@ -376,6 +449,9 @@ static int create_key_field(struct hist_trigger_data *hist_data,
 			flags |= HIST_FIELD_SYM;
 		else if (!strcmp(field_str, "sym-offset"))
 			flags |= HIST_FIELD_SYM_OFFSET;
+		else if (!strcmp(field_str, "execname") &&
+			 !strcmp(field_name, "common_pid"))
+			flags |= HIST_FIELD_EXECNAME;
 		else {
 			ret = -EINVAL;
 			goto out;
@@ -612,7 +688,7 @@ create_hist_data(unsigned int map_bits,
 		goto free;
 
 	hist_data->map = tracing_map_create(map_bits, hist_data->key_size,
-					    NULL, hist_data);
+					    &hist_trigger_ops, hist_data);
 	if (IS_ERR(hist_data->map)) {
 		ret = PTR_ERR(hist_data->map);
 		hist_data->map = NULL;
@@ -732,6 +808,12 @@ hist_trigger_entry_print(struct seq_file *m,
 			sprint_symbol(str, uval);
 			seq_printf(m, "%s: [%llx] %-55s",
 				   key_field->field->name, uval, str);
+		} else if (key_field->flags & HIST_FIELD_EXECNAME) {
+			char *comm = elt->private_data;
+
+			uval = *(u64 *)(key + key_field->offset);
+			seq_printf(m, "%s: %-16s[%10llu]",
+				   key_field->field->name, comm, uval);
 		} else if (key_field->flags & HIST_FIELD_STRING) {
 			seq_printf(m, "%s: %-50s", key_field->field->name,
 				   (char *)(key + key_field->offset));
@@ -851,6 +933,8 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
 		flags_str = "sym";
 	else if (hist_field->flags & HIST_FIELD_SYM_OFFSET)
 		flags_str = "sym-offset";
+	else if (hist_field->flags & HIST_FIELD_EXECNAME)
+		flags_str = "execname";
 
 	return flags_str;
 }
-- 
1.9.3