v4.19.13 snapshot.
diff --git a/kernel/trace/trace_stat.h b/kernel/trace/trace_stat.h
new file mode 100644
index 0000000..8786d17
--- /dev/null
+++ b/kernel/trace/trace_stat.h
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef __TRACE_STAT_H
+#define __TRACE_STAT_H
+
+#include <linux/seq_file.h>
+
+/*
+ * If you want to provide a stat file (one-shot statistics), fill
+ * an iterator with stat_start/stat_next and a stat_show callbacks.
+ * The others callbacks are optional.
+ */
+struct tracer_stat {
+ /* The name of your stat file */
+ const char *name;
+ /* Iteration over statistic entries */
+ void *(*stat_start)(struct tracer_stat *trace);
+ void *(*stat_next)(void *prev, int idx);
+ /* Compare two entries for stats sorting */
+ int (*stat_cmp)(void *p1, void *p2);
+ /* Print a stat entry */
+ int (*stat_show)(struct seq_file *s, void *p);
+ /* Release an entry */
+ void (*stat_release)(void *stat);
+ /* Print the headers of your stat entries */
+ int (*stat_headers)(struct seq_file *s);
+};
+
+/*
+ * Destroy or create a stat file
+ */
+extern int register_stat_tracer(struct tracer_stat *trace);
+extern void unregister_stat_tracer(struct tracer_stat *trace);
+
+#endif /* __TRACE_STAT_H */