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netronome: Replace zero-length array with flexible-array member
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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 7649773 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Gustavo A. R. Silva authored and David S. Miller committed Feb 24, 2020
1 parent f49b275 commit 3f6e963
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Showing 6 changed files with 12 additions and 12 deletions.
6 changes: 3 additions & 3 deletions drivers/net/ethernet/netronome/nfp/bpf/fw.h
Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand All @@ -120,6 +120,6 @@ struct cmsg_bpf_event {
__be64 map_ptr;
__be32 data_size;
__be32 pkt_size;
u8 data[0];
u8 data[];
};
#endif
4 changes: 2 additions & 2 deletions drivers/net/ethernet/netronome/nfp/flower/cmsg.h
Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand Down Expand Up @@ -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 {
Expand Down
2 changes: 1 addition & 1 deletion drivers/net/ethernet/netronome/nfp/nfp_main.h
Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,7 @@ struct nfp_shared_buf;
*/
struct nfp_dumpspec {
u32 size;
u8 data[0];
u8 data[];
};

/**
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8 changes: 4 additions & 4 deletions drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand All @@ -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 */
Expand All @@ -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 */
};

Expand All @@ -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 */
Expand Down
2 changes: 1 addition & 1 deletion drivers/net/ethernet/netronome/nfp/nfp_net_repr.h
Original file line number Diff line number Diff line change
Expand Up @@ -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[];
};

/**
Expand Down
2 changes: 1 addition & 1 deletion drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down

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