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

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

Link: https://lkml.kernel.org/r/20230606062027.1008398-5-sunliming@kylinos.cn

Acked-by: Beau Belgrave <beaub@linux.microsoft.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: sunliming <sunliming@kylinos.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: sunliming

tools/testing/selftests/user_events/perf_test.c

@@ -189,6 +189,59 @@ TEST_F(user, perf_write) {
 	ASSERT_EQ(0, self->check);
 }
 
+TEST_F(user, perf_empty_events) {
+	struct perf_event_attr pe = {0};
+	struct user_reg reg = {0};
+	struct perf_event_mmap_page *perf_page;
+	int page_size = sysconf(_SC_PAGESIZE);
+	int id, fd;
+	__u32 *val;
+
+	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);
+
+	/* Register should work */
+	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
+	ASSERT_EQ(0, reg.write_index);
+	ASSERT_EQ(0, self->check);
+
+	/* Id should be there */
+	id = get_id();
+	ASSERT_NE(-1, id);
+
+	pe.type = PERF_TYPE_TRACEPOINT;
+	pe.size = sizeof(pe);
+	pe.config = id;
+	pe.sample_type = PERF_SAMPLE_RAW;
+	pe.sample_period = 1;
+	pe.wakeup_events = 1;
+
+	/* Tracepoint attach should work */
+	fd = perf_event_open(&pe, 0, -1, -1, 0);
+	ASSERT_NE(-1, fd);
+
+	perf_page = mmap(NULL, page_size * 2, PROT_READ, MAP_SHARED, fd, 0);
+	ASSERT_NE(MAP_FAILED, perf_page);
+
+	/* Status should be updated */
+	ASSERT_EQ(1 << reg.enable_bit, self->check);
+
+	/* Ensure write shows up at correct offset */
+	ASSERT_NE(-1, write(self->data_fd, &reg.write_index,
+					sizeof(reg.write_index)));
+	val = (void *)(((char *)perf_page) + perf_page->data_offset);
+	ASSERT_EQ(PERF_RECORD_SAMPLE, *val);
+
+	munmap(perf_page, page_size * 2);
+	close(fd);
+
+	/* Status should be updated */
+	ASSERT_EQ(0, self->check);
+}
+
 int main(int argc, char **argv)
 {
 	return test_harness_run(argc, argv);