Add example how to enable/disable simple-pt in a program

onoff.c

@@ -0,0 +1,67 @@
+/* Demonstrate how to enable/disable simple-pt from a program */
+#include <stdio.h>
+#include <sys/fcntl.h>
+#include <unistd.h>
+
+#define noinline __attribute__((noinline))
+
+volatile int v;
+
+void sptcmd(int flag, char *fn)
+{
+	char buf[10];
+	int len = snprintf(buf, sizeof buf, "%d\n", flag);
+	int fd = open(fn, O_WRONLY);
+	if (fd >= 0) {
+		write(fd, buf, len);
+		close(fd);
+	}
+}
+
+void onoff(int flag)
+{
+	sptcmd(flag, "/sys/module/simple_pt/parameters/start");
+}
+
+void disable_clear(void)
+{
+	sptcmd(0, "/sys/module/simple_pt/parameters/clear_on_start");
+}
+
+noinline void f1(void)
+{
+	int i;
+	for (i = 0; i < 100; i++)
+		v++;
+}
+
+noinline void f2(void)
+{
+	int i;
+	for (i = 0; i < 100; i++)
+		v++;
+}
+
+noinline void f3(void)
+{
+	int i;
+	for (i = 0; i < 100; i++)
+		v++;
+}
+
+int main(void)
+{
+	onoff(1);
+	/* Disable clear on start */
+	disable_clear();
+	f1();
+	write(1, "foo\n", 4);
+	onoff(0);
+	f2();
+	write(1, "xyz\n", 4);
+	onoff(1);
+	f3();
+	write(1, "bar\n", 4);
+	onoff(0);
+	return 0;
+}