[PATCH v8 16/23] tracing: Add hist trigger 'execname' modifier

[Tom Zanussi]

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@xxxxxxxxxxxxxxx>
---
 kernel/trace/trace.c             |  1 +
 kernel/trace/trace_events_hist.c | 86 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 86 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8cdc7b3..a16ab69 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3816,6 +3816,7 @@ static const char readme_msg[] =
 	"\t            .hex        display a number as a hex value\n\n"
 	"\t            .sym        display an address as a symbol\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    By default, the size of the hash table is 2048 entries.  The\n"
 	"\t    'size' param can be used to specify more or fewer than that.\n"
 	"\t    The units are in terms of hashtable entries - if a run uses\n"
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 106d557..af1b846 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: %-35s", key_field->field->name,
 				   (char *)(key + key_field->offset));
@@ -845,6 +927,8 @@ 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

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