selftests/user_events: Add ftrace self-test for empty arguments events

Tests to ensure events that has empty arguments can input trace record
correctly when using ftrace.

Link: https://lkml.kernel.org/r/[email protected]

Acked-by: Beau Belgrave <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: sunliming <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: sunliming

tools/testing/selftests/user_events/ftrace_test.c

@@ -316,6 +316,39 @@ TEST_F(user, write_events) {
 	ASSERT_EQ(EINVAL, errno);
 }
 
+TEST_F(user, write_empty_events) {
+	struct user_reg reg = {0};
+	struct iovec io[1];
+	int before = 0, after = 0;
+
+	reg.size = sizeof(reg);
+	reg.name_args = (__u64)"__test_event";
+	reg.enable_bit = 31;
+	reg.enable_addr = (__u64)&self->check;
+	reg.enable_size = sizeof(self->check);
+
+	io[0].iov_base = &reg.write_index;
+	io[0].iov_len = sizeof(reg.write_index);
+
+	/* Register should work */
+	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
+	ASSERT_EQ(0, reg.write_index);
+	ASSERT_EQ(0, self->check);
+
+	/* Enable event */
+	self->enable_fd = open(enable_file, O_RDWR);
+	ASSERT_NE(-1, write(self->enable_fd, "1", sizeof("1")))
+
+	/* Event should now be enabled */
+	ASSERT_EQ(1 << reg.enable_bit, self->check);
+
+	/* Write should make it out to ftrace buffers */
+	before = trace_bytes();
+	ASSERT_NE(-1, writev(self->data_fd, (const struct iovec *)io, 1));
+	after = trace_bytes();
+	ASSERT_GT(after, before);
+}
+
 TEST_F(user, write_fault) {
 	struct user_reg reg = {0};
 	struct iovec io[2];