| Message ID | 20200507190750.GA15755@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | media: venus: Replace zero-length array with flexible-array | expand |
Hi Gustavo, Two patches from you are already queued in media_tree for v5.8. 0f61e171e4bbac4595175070c75707f1b12f4e37 media: venus: hfi_msgs.h: Replace zero-length array with flexible-array member 380f3bbd9562dc93be2e3cadc329b15284fbedae media: venus: hfi_cmds.h: Replace zero-length array with flexible-array member On 5/7/20 10:07 PM, Gustavo A. R. Silva wrote: > 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/media/platform/qcom/venus/hfi_cmds.h | 2 +- > drivers/media/platform/qcom/venus/hfi_msgs.h | 10 +++++----- > 2 files changed, 6 insertions(+), 6 deletions(-) > > diff --git a/drivers/media/platform/qcom/venus/hfi_cmds.h b/drivers/media/platform/qcom/venus/hfi_cmds.h > index cae9d5d61c0c..83705e237f1c 100644 > --- a/drivers/media/platform/qcom/venus/hfi_cmds.h > +++ b/drivers/media/platform/qcom/venus/hfi_cmds.h > @@ -107,7 +107,7 @@ struct hfi_session_abort_pkt { > struct hfi_session_set_property_pkt { > struct hfi_session_hdr_pkt shdr; > u32 num_properties; > - u32 data[0]; > + u32 data[]; > }; > > struct hfi_session_set_buffers_pkt { > diff --git a/drivers/media/platform/qcom/venus/hfi_msgs.h b/drivers/media/platform/qcom/venus/hfi_msgs.h > index 7694b1d25d9d..526d9f5b487b 100644 > --- a/drivers/media/platform/qcom/venus/hfi_msgs.h > +++ b/drivers/media/platform/qcom/venus/hfi_msgs.h > @@ -155,7 +155,7 @@ struct hfi_msg_session_empty_buffer_done_pkt { > u32 input_tag; > u32 packet_buffer; > u32 extradata_buffer; > - u32 data[0]; > + u32 data[]; > }; > > struct hfi_msg_session_fbd_compressed_pkt { > @@ -175,7 +175,7 @@ struct hfi_msg_session_fbd_compressed_pkt { > u32 picture_type; > u32 packet_buffer; > u32 extradata_buffer; > - u32 data[0]; > + u32 data[]; > }; > > struct hfi_msg_session_fbd_uncompressed_plane0_pkt { > @@ -202,7 +202,7 @@ struct hfi_msg_session_fbd_uncompressed_plane0_pkt { > u32 picture_type; > u32 packet_buffer; > u32 extradata_buffer; > - u32 data[0]; > + u32 data[]; > }; > > struct hfi_msg_session_fbd_uncompressed_plane1_pkt { > @@ -211,7 +211,7 @@ struct hfi_msg_session_fbd_uncompressed_plane1_pkt { > u32 filled_len; > u32 offset; > u32 packet_buffer2; > - u32 data[0]; > + u32 data[]; > }; > > struct hfi_msg_session_fbd_uncompressed_plane2_pkt { > @@ -220,7 +220,7 @@ struct hfi_msg_session_fbd_uncompressed_plane2_pkt { > u32 filled_len; > u32 offset; > u32 packet_buffer3; > - u32 data[0]; > + u32 data[]; > }; > > struct hfi_msg_session_parse_sequence_header_done_pkt { >
On Thu, May 07, 2020 at 11:39:51PM +0300, Stanimir Varbanov wrote: > Hi Gustavo, > > Two patches from you are already queued in media_tree for v5.8. > Awesome. :) Thanks, Stanimir. -- Gustavo > 0f61e171e4bbac4595175070c75707f1b12f4e37 media: venus: hfi_msgs.h: > Replace zero-length array with flexible-array member > > 380f3bbd9562dc93be2e3cadc329b15284fbedae media: venus: hfi_cmds.h: > Replace zero-length array with flexible-array member > > > On 5/7/20 10:07 PM, Gustavo A. R. Silva wrote: > > 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/media/platform/qcom/venus/hfi_cmds.h | 2 +- > > drivers/media/platform/qcom/venus/hfi_msgs.h | 10 +++++----- > > 2 files changed, 6 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/media/platform/qcom/venus/hfi_cmds.h b/drivers/media/platform/qcom/venus/hfi_cmds.h > > index cae9d5d61c0c..83705e237f1c 100644 > > --- a/drivers/media/platform/qcom/venus/hfi_cmds.h > > +++ b/drivers/media/platform/qcom/venus/hfi_cmds.h > > @@ -107,7 +107,7 @@ struct hfi_session_abort_pkt { > > struct hfi_session_set_property_pkt { > > struct hfi_session_hdr_pkt shdr; > > u32 num_properties; > > - u32 data[0]; > > + u32 data[]; > > }; > > > > struct hfi_session_set_buffers_pkt { > > diff --git a/drivers/media/platform/qcom/venus/hfi_msgs.h b/drivers/media/platform/qcom/venus/hfi_msgs.h > > index 7694b1d25d9d..526d9f5b487b 100644 > > --- a/drivers/media/platform/qcom/venus/hfi_msgs.h > > +++ b/drivers/media/platform/qcom/venus/hfi_msgs.h > > @@ -155,7 +155,7 @@ struct hfi_msg_session_empty_buffer_done_pkt { > > u32 input_tag; > > u32 packet_buffer; > > u32 extradata_buffer; > > - u32 data[0]; > > + u32 data[]; > > }; > > > > struct hfi_msg_session_fbd_compressed_pkt { > > @@ -175,7 +175,7 @@ struct hfi_msg_session_fbd_compressed_pkt { > > u32 picture_type; > > u32 packet_buffer; > > u32 extradata_buffer; > > - u32 data[0]; > > + u32 data[]; > > }; > > > > struct hfi_msg_session_fbd_uncompressed_plane0_pkt { > > @@ -202,7 +202,7 @@ struct hfi_msg_session_fbd_uncompressed_plane0_pkt { > > u32 picture_type; > > u32 packet_buffer; > > u32 extradata_buffer; > > - u32 data[0]; > > + u32 data[]; > > }; > > > > struct hfi_msg_session_fbd_uncompressed_plane1_pkt { > > @@ -211,7 +211,7 @@ struct hfi_msg_session_fbd_uncompressed_plane1_pkt { > > u32 filled_len; > > u32 offset; > > u32 packet_buffer2; > > - u32 data[0]; > > + u32 data[]; > > }; > > > > struct hfi_msg_session_fbd_uncompressed_plane2_pkt { > > @@ -220,7 +220,7 @@ struct hfi_msg_session_fbd_uncompressed_plane2_pkt { > > u32 filled_len; > > u32 offset; > > u32 packet_buffer3; > > - u32 data[0]; > > + u32 data[]; > > }; > > > > struct hfi_msg_session_parse_sequence_header_done_pkt { > > > > -- > regards, > Stan
diff --git a/drivers/media/platform/qcom/venus/hfi_cmds.h b/drivers/media/platform/qcom/venus/hfi_cmds.h index cae9d5d61c0c..83705e237f1c 100644 --- a/drivers/media/platform/qcom/venus/hfi_cmds.h +++ b/drivers/media/platform/qcom/venus/hfi_cmds.h @@ -107,7 +107,7 @@ struct hfi_session_abort_pkt { struct hfi_session_set_property_pkt { struct hfi_session_hdr_pkt shdr; u32 num_properties; - u32 data[0]; + u32 data[]; }; struct hfi_session_set_buffers_pkt { diff --git a/drivers/media/platform/qcom/venus/hfi_msgs.h b/drivers/media/platform/qcom/venus/hfi_msgs.h index 7694b1d25d9d..526d9f5b487b 100644 --- a/drivers/media/platform/qcom/venus/hfi_msgs.h +++ b/drivers/media/platform/qcom/venus/hfi_msgs.h @@ -155,7 +155,7 @@ struct hfi_msg_session_empty_buffer_done_pkt { u32 input_tag; u32 packet_buffer; u32 extradata_buffer; - u32 data[0]; + u32 data[]; }; struct hfi_msg_session_fbd_compressed_pkt { @@ -175,7 +175,7 @@ struct hfi_msg_session_fbd_compressed_pkt { u32 picture_type; u32 packet_buffer; u32 extradata_buffer; - u32 data[0]; + u32 data[]; }; struct hfi_msg_session_fbd_uncompressed_plane0_pkt { @@ -202,7 +202,7 @@ struct hfi_msg_session_fbd_uncompressed_plane0_pkt { u32 picture_type; u32 packet_buffer; u32 extradata_buffer; - u32 data[0]; + u32 data[]; }; struct hfi_msg_session_fbd_uncompressed_plane1_pkt { @@ -211,7 +211,7 @@ struct hfi_msg_session_fbd_uncompressed_plane1_pkt { u32 filled_len; u32 offset; u32 packet_buffer2; - u32 data[0]; + u32 data[]; }; struct hfi_msg_session_fbd_uncompressed_plane2_pkt { @@ -220,7 +220,7 @@ struct hfi_msg_session_fbd_uncompressed_plane2_pkt { u32 filled_len; u32 offset; u32 packet_buffer3; - u32 data[0]; + u32 data[]; }; struct hfi_msg_session_parse_sequence_header_done_pkt {
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/media/platform/qcom/venus/hfi_cmds.h | 2 +- drivers/media/platform/qcom/venus/hfi_msgs.h | 10 +++++----- 2 files changed, 6 insertions(+), 6 deletions(-)