1 files changed, 88 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/urandom_read.c b/tools/testing/selftests/bpf/urandom_read.c
new file mode 100644
index 000000000..e92644d0f
--- /dev/null
+++ b/tools/testing/selftests/bpf/urandom_read.c
@@ -0,0 +1,88 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <signal.h>
+
+#define _SDT_HAS_SEMAPHORES 1
+#include "sdt.h"
+
+#define SEC(name) __attribute__((section(name), used))
+
+#define BUF_SIZE 256
+
+/* defined in urandom_read_aux.c */
+void urand_read_without_sema(int iter_num, int iter_cnt, int read_sz);
+/* these are coming from urandom_read_lib{1,2}.c */
+void urandlib_read_with_sema(int iter_num, int iter_cnt, int read_sz);
+void urandlib_read_without_sema(int iter_num, int iter_cnt, int read_sz);
+
+unsigned short urand_read_with_sema_semaphore SEC(".probes");
+
+static __attribute__((noinline))
+void urandom_read(int fd, int count)
+{
+	char buf[BUF_SIZE];
+	int i;
+
+	for (i = 0; i < count; ++i) {
+		read(fd, buf, BUF_SIZE);
+
+		/* trigger USDTs defined in executable itself */
+		urand_read_without_sema(i, count, BUF_SIZE);
+		STAP_PROBE3(urand, read_with_sema, i, count, BUF_SIZE);
+
+		/* trigger USDTs defined in shared lib */
+		urandlib_read_without_sema(i, count, BUF_SIZE);
+		urandlib_read_with_sema(i, count, BUF_SIZE);
+	}
+}
+
+static volatile bool parent_ready;
+
+static void handle_sigpipe(int sig)
+{
+	parent_ready = true;
+}
+
+int main(int argc, char *argv[])
+{
+	int fd = open("/dev/urandom", O_RDONLY);
+	int count = 4;
+	bool report_pid = false;
+
+	if (fd < 0)
+		return 1;
+
+	if (argc >= 2)
+		count = atoi(argv[1]);
+	if (argc >= 3) {
+		report_pid = true;
+		/* install SIGPIPE handler to catch when parent closes their
+		 * end of the pipe (on the other side of our stdout)
+		 */
+		signal(SIGPIPE, handle_sigpipe);
+	}
+
+	/* report PID and wait for parent process to send us "signal" by
+	 * closing stdout
+	 */
+	if (report_pid) {
+		while (!parent_ready) {
+			fprintf(stdout, "%d\n", getpid());
+			fflush(stdout);
+		}
+		/* at this point stdout is closed, parent process knows our
+		 * PID and is ready to trace us
+		 */
+	}
+
+	urandom_read(fd, count);
+
+	close(fd);
+	return 0;
+}