sfc: falcon: use padding to fix alignment in loopback test

Add two bytes of padding to the start of struct ef4_loopback_payload,
 which are not sent on the wire.  This ensures the 'ip' member is
 4-byte aligned, preventing the following W=1 warning:
net/ethernet/sfc/falcon/selftest.c:43:15: error: field ip within 'struct ef4_loopback_payload' is less aligned than 'struct iphdr' and is usually due to 'struct ef4_loopback_payload' being packed, which can lead to unaligned accesses [-Werror,-Wunaligned-access]
        struct iphdr ip;

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/sfc/falcon/selftest.c b/drivers/net/ethernet/sfc/falcon/selftest.c
index 6a454ac..9e5ce2a 100644 (file)
--- a/drivers/net/ethernet/sfc/falcon/selftest.c
+++ b/drivers/net/ethernet/sfc/falcon/selftest.c
@@ -39,12 +39,16 @@
  * Falcon only performs RSS on TCP/UDP packets.
  */
 struct ef4_loopback_payload {
+       char pad[2]; /* Ensures ip is 4-byte aligned */
        struct ethhdr header;
        struct iphdr ip;
        struct udphdr udp;
        __be16 iteration;
        char msg[64];
-} __packed;
+} __packed __aligned(4);
+#define EF4_LOOPBACK_PAYLOAD_LEN       (sizeof(struct ef4_loopback_payload) - \
+                                        offsetof(struct ef4_loopback_payload, \
+                                                 header))
 
 /* Loopback test source MAC address */
 static const u8 payload_source[ETH_ALEN] __aligned(2) = {
@@ -284,7 +288,7 @@ void ef4_loopback_rx_packet(struct ef4_nic *efx,
                            const char *buf_ptr, int pkt_len)
 {
        struct ef4_loopback_state *state = efx->loopback_selftest;
-       struct ef4_loopback_payload *received;
+       struct ef4_loopback_payload received;
        struct ef4_loopback_payload *payload;
 
        BUG_ON(!buf_ptr);
@@ -295,13 +299,14 @@ void ef4_loopback_rx_packet(struct ef4_nic *efx,
 
        payload = &state->payload;
 
-       received = (struct ef4_loopback_payload *) buf_ptr;
-       received->ip.saddr = payload->ip.saddr;
+       memcpy(&received.header, buf_ptr,
+              min_t(int, pkt_len, EF4_LOOPBACK_PAYLOAD_LEN));
+       received.ip.saddr = payload->ip.saddr;
        if (state->offload_csum)
-               received->ip.check = payload->ip.check;
+               received.ip.check = payload->ip.check;
 
        /* Check that header exists */
-       if (pkt_len < sizeof(received->header)) {
+       if (pkt_len < sizeof(received.header)) {
                netif_err(efx, drv, efx->net_dev,
                          "saw runt RX packet (length %d) in %s loopback "
                          "test\n", pkt_len, LOOPBACK_MODE(efx));
@@ -309,7 +314,7 @@ void ef4_loopback_rx_packet(struct ef4_nic *efx,
        }
 
        /* Check that the ethernet header exists */
-       if (memcmp(&received->header, &payload->header, ETH_HLEN) != 0) {
+       if (memcmp(&received.header, &payload->header, ETH_HLEN) != 0) {
                netif_err(efx, drv, efx->net_dev,
                          "saw non-loopback RX packet in %s loopback test\n",
                          LOOPBACK_MODE(efx));
@@ -317,16 +322,16 @@ void ef4_loopback_rx_packet(struct ef4_nic *efx,
        }
 
        /* Check packet length */
-       if (pkt_len != sizeof(*payload)) {
+       if (pkt_len != EF4_LOOPBACK_PAYLOAD_LEN) {
                netif_err(efx, drv, efx->net_dev,
                          "saw incorrect RX packet length %d (wanted %d) in "
-                         "%s loopback test\n", pkt_len, (int)sizeof(*payload),
-                         LOOPBACK_MODE(efx));
+                         "%s loopback test\n", pkt_len,
+                         (int)EF4_LOOPBACK_PAYLOAD_LEN, LOOPBACK_MODE(efx));
                goto err;
        }
 
        /* Check that IP header matches */
-       if (memcmp(&received->ip, &payload->ip, sizeof(payload->ip)) != 0) {
+       if (memcmp(&received.ip, &payload->ip, sizeof(payload->ip)) != 0) {
                netif_err(efx, drv, efx->net_dev,
                          "saw corrupted IP header in %s loopback test\n",
                          LOOPBACK_MODE(efx));
@@ -334,7 +339,7 @@ void ef4_loopback_rx_packet(struct ef4_nic *efx,
        }
 
        /* Check that msg and padding matches */
-       if (memcmp(&received->msg, &payload->msg, sizeof(received->msg)) != 0) {
+       if (memcmp(&received.msg, &payload->msg, sizeof(received.msg)) != 0) {
                netif_err(efx, drv, efx->net_dev,
                          "saw corrupted RX packet in %s loopback test\n",
                          LOOPBACK_MODE(efx));
@@ -342,10 +347,10 @@ void ef4_loopback_rx_packet(struct ef4_nic *efx,
        }
 
        /* Check that iteration matches */
-       if (received->iteration != payload->iteration) {
+       if (received.iteration != payload->iteration) {
                netif_err(efx, drv, efx->net_dev,
                          "saw RX packet from iteration %d (wanted %d) in "
-                         "%s loopback test\n", ntohs(received->iteration),
+                         "%s loopback test\n", ntohs(received.iteration),
                          ntohs(payload->iteration), LOOPBACK_MODE(efx));
                goto err;
        }
@@ -365,7 +370,8 @@ void ef4_loopback_rx_packet(struct ef4_nic *efx,
                               buf_ptr, pkt_len, 0);
                netif_err(efx, drv, efx->net_dev, "expected packet:\n");
                print_hex_dump(KERN_ERR, "", DUMP_PREFIX_OFFSET, 0x10, 1,
-                              &state->payload, sizeof(state->payload), 0);
+                              &state->payload.header, EF4_LOOPBACK_PAYLOAD_LEN,
+                              0);
        }
 #endif
        atomic_inc(&state->rx_bad);
@@ -387,14 +393,15 @@ static void ef4_iterate_state(struct ef4_nic *efx)
        payload->ip.daddr = htonl(INADDR_LOOPBACK);
        payload->ip.ihl = 5;
        payload->ip.check = (__force __sum16) htons(0xdead);
-       payload->ip.tot_len = htons(sizeof(*payload) - sizeof(struct ethhdr));
+       payload->ip.tot_len = htons(sizeof(*payload) -
+                                   offsetof(struct ef4_loopback_payload, ip));
        payload->ip.version = IPVERSION;
        payload->ip.protocol = IPPROTO_UDP;
 
        /* Initialise udp header */
        payload->udp.source = 0;
-       payload->udp.len = htons(sizeof(*payload) - sizeof(struct ethhdr) -
-                                sizeof(struct iphdr));
+       payload->udp.len = htons(sizeof(*payload) -
+                                offsetof(struct ef4_loopback_payload, udp));
        payload->udp.check = 0; /* checksum ignored */
 
        /* Fill out payload */
@@ -420,7 +427,7 @@ static int ef4_begin_loopback(struct ef4_tx_queue *tx_queue)
        for (i = 0; i < state->packet_count; i++) {
                /* Allocate an skb, holding an extra reference for
                 * transmit completion counting */
-               skb = alloc_skb(sizeof(state->payload), GFP_KERNEL);
+               skb = alloc_skb(EF4_LOOPBACK_PAYLOAD_LEN, GFP_KERNEL);
                if (!skb)
                        return -ENOMEM;
                state->skbs[i] = skb;
@@ -431,6 +438,8 @@ static int ef4_begin_loopback(struct ef4_tx_queue *tx_queue)
                payload = skb_put(skb, sizeof(state->payload));
                memcpy(payload, &state->payload, sizeof(state->payload));
                payload->ip.saddr = htonl(INADDR_LOOPBACK | (i << 2));
+               /* Strip off the leading padding */
+               skb_pull(skb, offsetof(struct ef4_loopback_payload, header));
 
                /* Ensure everything we've written is visible to the
                 * interrupt handler. */