[PATCH 5/5] firewire: cdev: add KUnit test for bus reset event UAPI structure

[Takashi Sakamoto]

The bus reset event structure exposed through the UAPI has a different
size depending on the target architecture. Extra care is required when
copying it to/from userspace.

Add a KUnit test for the structure to ensure that it has the expected
size and offsets.
---
 drivers/firewire/core-cdev.c |  5 ++++-
 drivers/firewire/uapi-test.c | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index 50c675113d5c..6d91a6e7ad0d 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -524,7 +524,10 @@ static int ioctl_get_info(struct client *client, union ioctl_arg *arg)
 			memset(&bus_reset, 0, sizeof(bus_reset));
 			fill_bus_reset_event(&bus_reset, client);
 
-			/* unaligned size of bus_reset is 36 bytes */
+			// This structure has 4 bytes of trailing padding under the System V ABI
+			// on most architectures (due to 8-byte alignment of the long long type),
+			// except for Intel386 (where long long type is aligned to 4 bytes). In
+			// either case, the effective length is 36 bytes.
 			if (copy_to_user(u64_to_uptr(a->bus_reset), &bus_reset, 36))
 				return -EFAULT;
 		}
diff --git a/drivers/firewire/uapi-test.c b/drivers/firewire/uapi-test.c
index bc3f10a2e516..0bdacb1caeb8 100644
--- a/drivers/firewire/uapi-test.c
+++ b/drivers/firewire/uapi-test.c
@@ -72,11 +72,31 @@ static void structure_layout_event_phy_packet2(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_phy_packet2, data));
 }
 
+static void structure_layout_event_bus_reset(struct kunit *test)
+{
+#if defined(CONFIG_X86_32)
+       // 4 bytes alignment for aggregate type including 8 bytes storage types.
+       KUNIT_EXPECT_EQ(test, 36, sizeof(struct fw_cdev_event_bus_reset));
+#else
+       KUNIT_EXPECT_EQ(test, 40, sizeof(struct fw_cdev_event_bus_reset));
+#endif
+
+       KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_bus_reset, closure));
+       KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_bus_reset, type));
+       KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_bus_reset, node_id));
+       KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_bus_reset, local_node_id));
+       KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_bus_reset, bm_node_id));
+       KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_bus_reset, irm_node_id));
+       KUNIT_EXPECT_EQ(test, 28, offsetof(struct fw_cdev_event_bus_reset, root_node_id));
+       KUNIT_EXPECT_EQ(test, 32, offsetof(struct fw_cdev_event_bus_reset, generation));
+}
+
 static struct kunit_case structure_layout_test_cases[] = {
 	KUNIT_CASE(structure_layout_event_response),
 	KUNIT_CASE(structure_layout_event_request3),
 	KUNIT_CASE(structure_layout_event_response2),
 	KUNIT_CASE(structure_layout_event_phy_packet2),
+	KUNIT_CASE(structure_layout_event_bus_reset),
 	{}
 };
 
-- 
2.53.0