Re: [Intel-wired-lan] [PATCH net v2 1/3] xsk: align TX metadata layout across ABIs
Simon Horman <[email protected]>
| Newsgroups | org.osuosl.intel-wired-lan,org.infradead.lists.linux-arm-kernel,org.kernel.vger.bpf,org.kernel.vger.linux-kernel,org.kernel.vger.linux-rdma,org.kernel.vger.netdev |
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| Message-ID | <[email protected]> |
On Thu, Aug 13, 2026 at 12:07:58PM -0700, Stanislav Fomichev wrote:
> Add explicit padding before launch_time so xsk_tx_metadata has the same
> layout on 32-bit and 64-bit systems.
>
> On i386 and m68k, the old native 32-bit layout put launch_time at offset 12
> and had a natural size of 20 bytes. Using sizeof(struct xsk_tx_metadata) as
> tx_metadata_len was already rejected because the length must be a multiple
> of eight, so the straightforward use of the interface was broken on those
> ABIs. Userspace could still register a padded length of 24 bytes, though;
> mixing the old and new layouts then silently reads launch_time from the
> wrong offset and misprograms packet launch times. This intentionally
> replaces that incompatible layout while the interface is still new.
>
> Fixes: ca4419f15abd ("xsk: Add launch time hardware offload support to XDP Tx metadata")
> Signed-off-by: Stanislav Fomichev <[email protected]>
Reviewed-by: Simon Horman <[email protected]>