util/trace: add ftrace utilities

include/util/trace.h

@@ -0,0 +1,9 @@
+#ifndef UTIL_TRACE_H
+#define UTIL_TRACE_H
+
+#include <wlr/util/log.h>
+
+void wlr_trace(const char *format, ...) _WLR_ATTRIB_PRINTF(1, 2);
+void wlr_vtrace(const char *format, va_list args) _WLR_ATTRIB_PRINTF(1, 0);
+
+#endif

util/meson.build

@@ -13,6 +13,7 @@ wlr_files += files(
 	'shm.c',
 	'time.c',
 	'token.c',
+	'trace.c',
 	'transform.c',
 	'utf8.c',
 )

util/trace.c

@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include "util/trace.h"
+
+static bool trace_initialized = false;
+static FILE *trace_file = NULL;
+
+void wlr_vtrace(const char *fmt, va_list args) {
+	if (!trace_initialized) {
+		trace_initialized = true;
+		trace_file = fopen("/sys/kernel/tracing/trace_marker", "w");
+		if (trace_file != NULL) {
+			wlr_log(WLR_INFO, "Kernel tracing is enabled");
+		}
+	}
+
+	if (trace_file == NULL) {
+		return;
+	}
+
+	vfprintf(trace_file, fmt, args);
+	fprintf(trace_file, "\n");
+	fflush(trace_file);
+}
+
+void wlr_trace(const char *fmt, ...) {
+	va_list args;
+	va_start(args, fmt);
+	wlr_vtrace(fmt, args);
+	va_end(args);
+}