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sfc: falcon: use padding to fix alignment in loopback test
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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 <[email protected]>
Signed-off-by: Edward Cree <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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@davem330
Edward Cree authored and davem330 committed Jun 26, 2023
1 parent 30c24dd commit 1186c6b
Showing 1 changed file with 28 additions and 19 deletions.
47 changes: 28 additions & 19 deletions drivers/net/ethernet/sfc/falcon/selftest.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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) = {
Expand Down Expand Up @@ -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);
Expand All @@ -295,57 +299,58 @@ 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));
goto err;
}

/* 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));
goto err;
}

/* 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));
goto err;
}

/* 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));
goto err;
}

/* 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;
}
Expand All @@ -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);
Expand All @@ -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 */
Expand All @@ -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;
Expand All @@ -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. */
Expand Down

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