efi_selftest: test exit_data

Amend the unit test 'start image exit' to transfer a string as exit data.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_selftest/efi_selftest_startimage_exit.c b/lib/efi_selftest/efi_selftest_startimage_exit.c
index fa4b7d4..96049de 100644
--- a/lib/efi_selftest/efi_selftest_startimage_exit.c
+++ b/lib/efi_selftest/efi_selftest_startimage_exit.c
@@ -123,6 +123,9 @@
 {
 	efi_status_t ret;
 	efi_handle_t handle;
+	efi_uintn_t exit_data_size = 0;
+	u16 *exit_data = NULL;
+	u16 expected_text[] = EFI_ST_SUCCESS_STR;
 
 	ret = boottime->load_image(false, image_handle, NULL, image,
 				   img.length, &handle);
@@ -130,11 +133,21 @@
 		efi_st_error("Failed to load image\n");
 		return EFI_ST_FAILURE;
 	}
-	ret = boottime->start_image(handle, NULL, NULL);
+	ret = boottime->start_image(handle, &exit_data_size, &exit_data);
 	if (ret != EFI_UNSUPPORTED) {
 		efi_st_error("Wrong return value from application\n");
 		return EFI_ST_FAILURE;
 	}
+	if (!exit_data || exit_data_size != sizeof(expected_text) ||
+	    efi_st_memcmp(exit_data, expected_text, sizeof(expected_text))) {
+		efi_st_error("Incorrect exit data\n");
+		return EFI_ST_FAILURE;
+	}
+	ret = boottime->free_pool(exit_data);
+	if (ret != EFI_SUCCESS) {
+		efi_st_error("Failed to free exit data\n");
+		return EFI_ST_FAILURE;
+	}
 
 	return EFI_ST_SUCCESS;
 }