[PATCH] staging: greybus: Replace zero-length array with flexible-array
From: Gustavo A. R. Silva
Date: Thu May 07 2020 - 14:48:55 EST
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@xxxxxxxxxx>
---
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 */