From: Marc Kleine-Budde mkl@pengutronix.de
commit a4cb6e62ea4d36e53fb3c0f18ea4503d7b76674f upstream.
clang emits a -Wunaligned-access warning on struct __packed ems_cpc_msg.
The reason is that the anonymous union msg (not declared as packed) is being packed right after some non naturally aligned variables (3*8 bits + 2*32) inside a packed struct:
| struct __packed ems_cpc_msg { | u8 type; /* type of message */ | u8 length; /* length of data within union 'msg' */ | u8 msgid; /* confirmation handle */ | __le32 ts_sec; /* timestamp in seconds */ | __le32 ts_nsec; /* timestamp in nano seconds */ | /* ^ not naturally aligned */ | | union { | /* ^ not declared as packed */ | u8 generic[64]; | struct cpc_can_msg can_msg; | struct cpc_can_params can_params; | struct cpc_confirm confirmation; | struct cpc_overrun overrun; | struct cpc_can_error error; | struct cpc_can_err_counter err_counter; | u8 can_state; | } msg; | };
Starting from LLVM 14, having an unpacked struct nested in a packed struct triggers a warning. c.f. [1].
Fix the warning by marking the anonymous union as packed.
[1] https://github.com/llvm/llvm-project/issues/55520
Fixes: 702171adeed3 ("ems_usb: Added support for EMS CPC-USB/ARM7 CAN/USB interface") Link: https://lore.kernel.org/all/20220802094021.959858-1-mkl@pengutronix.de Cc: Gerhard Uttenthaler uttenthaler@ems-wuensche.com Cc: Sebastian Haas haas@ems-wuensche.com Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/can/usb/ems_usb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/net/can/usb/ems_usb.c +++ b/drivers/net/can/usb/ems_usb.c @@ -194,7 +194,7 @@ struct __packed ems_cpc_msg { __le32 ts_sec; /* timestamp in seconds */ __le32 ts_nsec; /* timestamp in nano seconds */
- union { + union __packed { u8 generic[64]; struct cpc_can_msg can_msg; struct cpc_can_params can_params;