On Thu, Apr 14, 2022 at 10:47:20PM +0000, Alexander Lobakin wrote:
> Fix two sort-of-false-positives in the xdpsock userspace part:
>
> samples/bpf/xdpsock_user.c: In function 'main':
> samples/bpf/xdpsock_user.c:1531:47: warning: 'tv_usec' may be used uninitialized in this function [-Wmaybe-uninitialized]
> 1531 | pktgen_hdr->tv_usec = htonl(tv_usec);
> | ^~~~~~~~~~~~~~
> samples/bpf/xdpsock_user.c:1500:26: note: 'tv_usec' was declared here
> 1500 | u32 idx, tv_sec, tv_usec;
> | ^~~~~~~
> samples/bpf/xdpsock_user.c:1530:46: warning: 'tv_sec' may be used uninitialized in this function [-Wmaybe-uninitialized]
> 1530 | pktgen_hdr->tv_sec = htonl(tv_sec);
> | ^~~~~~~~~~~~~
> samples/bpf/xdpsock_user.c:1500:18: note: 'tv_sec' was declared here
> 1500 | u32 idx, tv_sec, tv_usec;
> | ^~~~~~
>
> Both variables are always initialized when @opt_tstamp == true and
> they're being used also only when @opt_tstamp == true. However, that
> variable comes from the BSS and is being toggled from another
> function. They can't be executed simultaneously to actually trigger
> undefined behaviour, but purely technically it is a correct warning.
> Just initialize them with zeroes.
>
> Fixes: eb68db45b747 ("samples/bpf: xdpsock: Add timestamp for Tx-only operation")
> Signed-off-by: Alexander Lobakin <alobakin@xxxxx>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
Magnus would tell you that you should fix this on libxdp side instead :)
> ---
> samples/bpf/xdpsock_user.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
> index 399b999fcec2..1dc7ad5dbef4 100644
> --- a/samples/bpf/xdpsock_user.c
> +++ b/samples/bpf/xdpsock_user.c
> @@ -1496,7 +1496,7 @@ static void rx_drop_all(void)
> static int tx_only(struct xsk_socket_info *xsk, u32 *frame_nb,
> int batch_size, unsigned long tx_ns)
> {
> - u32 idx, tv_sec, tv_usec;
> + u32 idx, tv_sec = 0, tv_usec = 0;
> unsigned int i;
>
> while (xsk_ring_prod__reserve(&xsk->tx, batch_size, &idx) <
> --
> 2.35.2
>
>
