netronome: Replace zero-length array with flexible-array member

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]

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 <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/fw.h b/drivers/net/ethernet/netronome/nfp/bpf/fw.h
index a83a0ad..4268a7e 100644 (file)
--- a/drivers/net/ethernet/netronome/nfp/bpf/fw.h
+++ b/drivers/net/ethernet/netronome/nfp/bpf/fw.h
@@ -104,14 +104,14 @@ struct cmsg_req_map_op {
        __be32 tid;
        __be32 count;
        __be32 flags;
-       u8 data[0];
+       u8 data[];
 };
 
 struct cmsg_reply_map_op {
        struct cmsg_reply_map_simple reply_hdr;
        __be32 count;
        __be32 resv;
-       u8 data[0];
+       u8 data[];
 };
 
 struct cmsg_bpf_event {
@@ -120,6 +120,6 @@ struct cmsg_bpf_event {
        __be64 map_ptr;
        __be32 data_size;
        __be32 pkt_size;
-       u8 data[0];
+       u8 data[];
 };
 #endif

diff --git a/drivers/net/ethernet/netronome/nfp/flower/cmsg.h b/drivers/net/ethernet/netronome/nfp/flower/cmsg.h
index 9b50d76..bf51628 100644 (file)
--- a/drivers/net/ethernet/netronome/nfp/flower/cmsg.h
+++ b/drivers/net/ethernet/netronome/nfp/flower/cmsg.h
@@ -587,7 +587,7 @@ struct nfp_flower_cmsg_mac_repr {
                u8 info;
                u8 nbi_port;
                u8 phys_port;
-       } ports[0];
+       } ports[];
 };
 
 #define NFP_FLOWER_CMSG_MAC_REPR_NBI           GENMASK(1, 0)
@@ -619,7 +619,7 @@ struct nfp_flower_cmsg_merge_hint {
        struct {
                __be32 host_ctx;
                __be64 host_cookie;
-       } __packed flow[0];
+       } __packed flow[];
 };
 
 enum nfp_flower_cmsg_port_type {

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_main.h b/drivers/net/ethernet/netronome/nfp/nfp_main.h
index 5d5812f..fa6b13a 100644 (file)
--- a/drivers/net/ethernet/netronome/nfp/nfp_main.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_main.h
@@ -42,7 +42,7 @@ struct nfp_shared_buf;
  */
 struct nfp_dumpspec {
        u32 size;
-       u8 data[0];
+       u8 data[];
 };
 
 /**

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
index 769ceef..a614df0 100644 (file)
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
@@ -36,7 +36,7 @@ enum nfp_dumpspec_type {
 struct nfp_dump_tl {
        __be32 type;
        __be32 length;  /* chunk length to follow, aligned to 8 bytes */
-       char data[0];
+       char data[];
 };
 
 /* NFP CPP parameters */
@@ -62,7 +62,7 @@ struct nfp_dumpspec_csr {
 
 struct nfp_dumpspec_rtsym {
        struct nfp_dump_tl tl;
-       char rtsym[0];
+       char rtsym[];
 };
 
 /* header for register dumpable */
@@ -79,7 +79,7 @@ struct nfp_dump_rtsym {
        struct nfp_dump_common_cpp cpp;
        __be32 error;           /* error code encountered while reading */
        u8 padded_name_length;  /* pad so data starts at 8 byte boundary */
-       char rtsym[0];
+       char rtsym[];
        /* after padded_name_length, there is dump_length data */
 };
 
@@ -92,7 +92,7 @@ struct nfp_dump_error {
        struct nfp_dump_tl tl;
        __be32 error;
        char padding[4];
-       char spec[0];
+       char spec[];
 };
 
 /* to track state through debug size calculation TLV traversal */

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.h b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.h
index e0f13df..48a74ac 100644 (file)
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.h
@@ -18,7 +18,7 @@ struct nfp_port;
  */
 struct nfp_reprs {
        unsigned int num_reprs;
-       struct net_device __rcu *reprs[0];
+       struct net_device __rcu *reprs[];
 };
 
 /**

diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h
index 1531c18..f5360ba 100644 (file)
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h
@@ -183,7 +183,7 @@ struct nfp_eth_table {
                bool is_split;
 
                unsigned int fec_modes_supported;
-       } ports[0];
+       } ports[];
 };
 
 struct nfp_eth_table *nfp_eth_read_ports(struct nfp_cpp *cpp);