From 529798bae7c155d38eec211436df736349dca2ee Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 7 May 2020 14:19:43 -0500 Subject: [PATCH] remoteproc: Replace zero-length array with flexible-array 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 Link: https://lore.kernel.org/r/20200507191943.GA16033@embeddedor Signed-off-by: Bjorn Andersson --- include/linux/remoteproc.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h index 0468be4d02f4..e7b7bab8b235 100644 --- a/include/linux/remoteproc.h +++ b/include/linux/remoteproc.h @@ -73,7 +73,7 @@ struct resource_table { u32 ver; u32 num; u32 reserved[2]; - u32 offset[0]; + u32 offset[]; } __packed; /** @@ -87,7 +87,7 @@ struct resource_table { */ struct fw_rsc_hdr { u32 type; - u8 data[0]; + u8 data[]; } __packed; /** @@ -306,7 +306,7 @@ struct fw_rsc_vdev { u8 status; u8 num_of_vrings; u8 reserved[2]; - struct fw_rsc_vdev_vring vring[0]; + struct fw_rsc_vdev_vring vring[]; } __packed; struct rproc;