On Tue, 31 Mar 2020 15:08:26 +0100
Kevin Traynor <ktray...@redhat.com> wrote:
> struct virtchnl_rss_key {
> u16 vsi_id;
> u16 key_len;
> u8 key[1]; /* RSS hash key, packed bytes */
> ^^^^^^^^^
> };
>
> Then in iavf_configure_rss_key()
>
> len = sizeof(*rss_key) + vf->vf_res->rss_key_size - 1;
> ^^^^^^^^^^^^
> rss_key = rte_zmalloc("rss_key", len, 0);
> ^^^ extra space beyond key[1] allocated here
>
> <snip>
> rte_memcpy(rss_key->key, vf->rss_key, vf->vf_res->rss_key_size);
> ^^^ ^^^^^^^^^^^^
>
> At runtime we have allocated extra space at the end of the struct for
> key, and the same size used in the malloc is also considered when
> finding the right branches in the memcpy fns. But the compiler does not
> know value of size and it simply sees there can be casts of a 1 byte key
> to 16 or 32 bytes in some branches of the memcpy fns, so gives a warning.
The standard way to do such a thing is to use an empty
array. The Linux kernel has just gone through cleaning up
all these zero length (and it this case one) array at
end of function.
