libtraceevent: Add reading func_repeats events to function plugin

With the new ftrace event func_repeats coming to the kernel, add processing
the output of it so it fits right in with the function tracer.

Since it uses the same event fields as the function trace, it can call the
function handler first, which will process the func_repeats event just like
a function, and then print the count and convert the delta to display the
actual timestamp of the last function that repeated.

Add a weak variable called "tep_func_repeat_format" to allow applications
to override how the timestamp of the last function is displayed.

Link: https://lore.kernel.org/linux-trace-devel/20210413170756.3c4638f9@gandalf.local.home

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 38 insertions, 0 deletions

diff --git a/plugins/plugin_function.c b/plugins/plugin_function.c
index 93bdcc2..7777569 100644
--- a/plugins/plugin_function.c
+++ b/plugins/plugin_function.c
@@ -10,6 +10,11 @@
 #include "event-utils.h"
 #include "trace-seq.h"
 
+#define __weak __attribute__((weak))
+
+/* Export this for applications to override it */
+__weak const char *tep_func_repeat_format = "%6.1000d";
+
 static struct func_stack {
 	int size;
 	char **stack;
@@ -169,6 +174,36 @@ static int function_handler(struct trace_seq *s, struct tep_record *record,
 	return 0;
 }
 
+static int trace_func_repeat_handler(struct trace_seq *s, struct tep_record *record,
+				    struct tep_event *event, void *context)
+{
+	struct tep_handle *tep = event->tep;
+	unsigned long long count, top_delta, bottom_delta;
+	struct tep_record dummy;
+
+	function_handler(s, record, event, context);
+
+	if (tep_get_field_val(s, event, "count", record, &count, 1))
+		return trace_seq_putc(s, '!');
+
+	if (tep_get_field_val(s, event, "top_delta_ts", record, &top_delta, 1))
+		return trace_seq_putc(s, '!');
+
+	if (tep_get_field_val(s, event, "bottom_delta_ts", record, &bottom_delta, 1))
+		return trace_seq_putc(s, '!');
+
+	trace_seq_printf(s, " (count: %lld  last_ts: ", count);
+
+	memcpy(&dummy, record, sizeof(dummy));
+	dummy.ts -= (top_delta << 32) | bottom_delta;
+
+	tep_print_event(tep, s, &dummy, tep_func_repeat_format, TEP_PRINT_TIME);
+
+	trace_seq_puts(s, ")");
+
+	return 0;
+}
+
 static int
 trace_stack_handler(struct trace_seq *s, struct tep_record *record,
 		    struct tep_event *event, void *context)
@@ -256,6 +291,9 @@ int TEP_PLUGIN_LOADER(struct tep_handle *tep)
 	tep_register_event_handler(tep, -1, "ftrace", "raw_data",
 				      trace_raw_data_handler, NULL);
 
+	tep_register_event_handler(tep, -1, "ftrace", "func_repeats",
+				      trace_func_repeat_handler, NULL);
+
 	tep_plugin_add_options("ftrace", plugin_options);
 
 	return 0;