The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99:
struct foo { int stuff; struct boo array[]; };
By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by this change:
"Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1]
sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues.
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva gustavoars@kernel.org --- drivers/greybus/arpc.h | 2 - include/linux/greybus/greybus_protocols.h | 44 +++++++++++++++--------------- 2 files changed, 23 insertions(+), 23 deletions(-)
diff --git a/drivers/greybus/arpc.h b/drivers/greybus/arpc.h index c8b83c5cfa79..b9ea81b55b29 100644 --- a/drivers/greybus/arpc.h +++ b/drivers/greybus/arpc.h @@ -21,7 +21,7 @@ struct arpc_request_message { __le16 id; /* RPC unique id */ __le16 size; /* Size in bytes of header + payload */ __u8 type; /* RPC type */ - __u8 data[0]; /* ARPC data */ + __u8 data[]; /* ARPC data */ } __packed;
struct arpc_response_message { diff --git a/include/linux/greybus/greybus_protocols.h b/include/linux/greybus/greybus_protocols.h index dfbc6c39a74b..aeb8f9243545 100644 --- a/include/linux/greybus/greybus_protocols.h +++ b/include/linux/greybus/greybus_protocols.h @@ -345,7 +345,7 @@ struct gb_cap_get_ims_certificate_request {
struct gb_cap_get_ims_certificate_response { __u8 result_code; - __u8 certificate[0]; + __u8 certificate[]; } __packed;
/* CAP authenticate request/response */ @@ -358,7 +358,7 @@ struct gb_cap_authenticate_request { struct gb_cap_authenticate_response { __u8 result_code; __u8 response[64]; - __u8 signature[0]; + __u8 signature[]; } __packed;
@@ -642,7 +642,7 @@ struct gb_hid_get_report_request { struct gb_hid_set_report_request { __u8 report_type; __u8 report_id; - __u8 report[0]; + __u8 report[]; } __packed;
/* HID input report request, via interrupt pipe */ @@ -680,7 +680,7 @@ struct gb_i2c_transfer_op {
struct gb_i2c_transfer_request { __le16 op_count; - struct gb_i2c_transfer_op ops[0]; /* op_count of these */ + struct gb_i2c_transfer_op ops[]; /* op_count of these */ } __packed; struct gb_i2c_transfer_response { __u8 data[0]; /* inbound data */ @@ -908,7 +908,7 @@ struct gb_spi_transfer_request { __u8 chip_select; /* of the spi device */ __u8 mode; /* of the spi device */ __le16 count; - struct gb_spi_transfer transfers[0]; /* count of these */ + struct gb_spi_transfer transfers[]; /* count of these */ } __packed;
struct gb_spi_transfer_response { @@ -1188,7 +1188,7 @@ struct gb_svc_pwrmon_rail_count_get_response {
struct gb_svc_pwrmon_rail_names_get_response { __u8 status; - __u8 name[0][GB_SVC_PWRMON_RAIL_NAME_BUFSIZE]; + __u8 name[][GB_SVC_PWRMON_RAIL_NAME_BUFSIZE]; } __packed;
#define GB_SVC_PWRMON_TYPE_CURR 0x01 @@ -1281,7 +1281,7 @@ struct gb_svc_intf_oops_request {
struct gb_raw_send_request { __le32 len; - __u8 data[0]; + __u8 data[]; } __packed;
@@ -1300,7 +1300,7 @@ struct gb_raw_send_request { /* Represents data from AP -> Module */ struct gb_uart_send_data_request { __le16 size; - __u8 data[0]; + __u8 data[]; } __packed;
/* recv-data-request flags */ @@ -1313,7 +1313,7 @@ struct gb_uart_send_data_request { struct gb_uart_recv_data_request { __le16 size; __u8 flags; - __u8 data[0]; + __u8 data[]; } __packed;
struct gb_uart_receive_credits_request { @@ -1382,14 +1382,14 @@ struct gb_loopback_transfer_request { __le32 len; __le32 reserved0; __le32 reserved1; - __u8 data[0]; + __u8 data[]; } __packed;
struct gb_loopback_transfer_response { __le32 len; __le32 reserved0; __le32 reserved1; - __u8 data[0]; + __u8 data[]; } __packed;
/* SDIO */ @@ -1530,13 +1530,13 @@ struct gb_sdio_transfer_request {
__le16 data_blocks; __le16 data_blksz; - __u8 data[0]; + __u8 data[]; } __packed;
struct gb_sdio_transfer_response { __le16 data_blocks; __le16 data_blksz; - __u8 data[0]; + __u8 data[]; } __packed;
/* event request: generated by module and is defined as unidirectional */ @@ -1572,7 +1572,7 @@ struct gb_camera_configure_streams_request { __u8 flags; #define GB_CAMERA_CONFIGURE_STREAMS_TEST_ONLY 0x01 __le16 padding; - struct gb_camera_stream_config_request config[0]; + struct gb_camera_stream_config_request config[]; } __packed;
/* Greybus Camera Configure Streams response payload */ @@ -1593,7 +1593,7 @@ struct gb_camera_configure_streams_response { __u8 flags; __u8 padding[2]; __le32 data_rate; - struct gb_camera_stream_config_response config[0]; + struct gb_camera_stream_config_response config[]; };
/* Greybus Camera Capture request payload - response has no payload */ @@ -1602,7 +1602,7 @@ struct gb_camera_capture_request { __u8 streams; __u8 padding; __le16 num_frames; - __u8 settings[0]; + __u8 settings[]; } __packed;
/* Greybus Camera Flush response payload - request has no payload */ @@ -1616,7 +1616,7 @@ struct gb_camera_metadata_request { __le16 frame_number; __u8 stream; __u8 padding; - __u8 metadata[0]; + __u8 metadata[]; } __packed;
/* Lights */ @@ -1993,7 +1993,7 @@ struct gb_audio_integer64 { struct gb_audio_enumerated { __le32 items; __le16 names_length; - __u8 names[0]; + __u8 names[]; } __packed;
struct gb_audio_ctl_elem_info { /* See snd_ctl_elem_info in Linux source */ @@ -2033,7 +2033,7 @@ struct gb_audio_widget { __u8 type; /* GB_AUDIO_WIDGET_TYPE_* */ __u8 state; /* GB_AUDIO_WIDGET_STATE_* */ __u8 ncontrols; - struct gb_audio_control ctl[0]; /* 'ncontrols' entries */ + struct gb_audio_control ctl[]; /* 'ncontrols' entries */ } __packed;
struct gb_audio_route { @@ -2059,7 +2059,7 @@ struct gb_audio_topology { * struct gb_audio_widget widgets[num_widgets]; * struct gb_audio_route routes[num_routes]; */ - __u8 data[0]; + __u8 data[]; } __packed;
struct gb_audio_get_topology_size_response { @@ -2157,7 +2157,7 @@ struct gb_audio_streaming_event_request {
struct gb_audio_send_data_request { __le64 timestamp; - __u8 data[0]; + __u8 data[]; } __packed;
@@ -2171,7 +2171,7 @@ struct gb_audio_send_data_request {
struct gb_log_send_log_request { __le16 len; - __u8 msg[0]; + __u8 msg[]; } __packed;
#endif /* __GREYBUS_PROTOCOLS_H */