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| author | Gustavo A. R. Silva <gustavo@embeddedor.com> | 2020-02-28 07:19:07 -0600 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2020-02-28 12:08:37 -0800 |
| commit | 95e486f5519848ca4c2f2645cbe120de5df133f3 (patch) | |
| tree | 937b075552d32f6f0eb131a5ec25565d7835d0d3 | |
| parent | 549da33801266c6cb04431add7c205bb43e93acf (diff) | |
| download | linux-95e486f5519848ca4c2f2645cbe120de5df133f3.tar.bz2 | |
xdp: 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>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/xdp/xsk_queue.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h index 89a01ac4e079..b50bb5c76da5 100644 --- a/net/xdp/xsk_queue.h +++ b/net/xdp/xsk_queue.h @@ -19,13 +19,13 @@ struct xdp_ring { /* Used for the RX and TX queues for packets */ struct xdp_rxtx_ring { struct xdp_ring ptrs; - struct xdp_desc desc[0] ____cacheline_aligned_in_smp; + struct xdp_desc desc[] ____cacheline_aligned_in_smp; }; /* Used for the fill and completion queues for buffers */ struct xdp_umem_ring { struct xdp_ring ptrs; - u64 desc[0] ____cacheline_aligned_in_smp; + u64 desc[] ____cacheline_aligned_in_smp; }; struct xsk_queue { |