gve: Use ethtool_sprintf/puts() to fill stats strings

Make use of standard helpers to simplify filling in stats strings.

The first two ethtool_puts() changes address the following fortification
warnings flagged by W=1 builds with clang-18. (The last ethtool_puts
change does not because the warning relates to writing beyond the first
element of an array, and gve_gstrings_priv_flags only has one element.)

.../fortify-string.h:562:4: warning: call to '__read_overflow2_field' declared with 'warning' attribute: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Wattribute-warning]
  562 |                         __read_overflow2_field(q_size_field, size);
      |                         ^
.../fortify-string.h:562:4: warning: call to '__read_overflow2_field' declared with 'warning' attribute: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Wattribute-warning]

Likewise, the same changes resolve the same problems flagged by Smatch.

.../gve_ethtool.c:100 gve_get_strings() error: __builtin_memcpy() '*gve_gstrings_main_stats' too small (32 vs 576)
.../gve_ethtool.c:120 gve_get_strings() error: __builtin_memcpy() '*gve_gstrings_adminq_stats' too small (32 vs 512)

Compile tested only.

Reviewed-by: Shailend Chand <shailend@google.com>
Reviewed-by: Larysa Zaremba <larysa.zaremba@intel.com>
Signed-off-by: Simon Horman <horms@kernel.org>
Acked-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240508-gve-comma-v2-2-1ac919225f13@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: horms

drivers/net/ethernet/google/gve/gve_ethtool.c

@@ -90,42 +90,34 @@ static const char gve_gstrings_priv_flags[][ETH_GSTRING_LEN] = {
 static void gve_get_strings(struct net_device *netdev, u32 stringset, u8 *data)
 {
 	struct gve_priv *priv = netdev_priv(netdev);
-	char *s = (char *)data;
+	u8 *s = (char *)data;
 	int num_tx_queues;
 	int i, j;
 
 	num_tx_queues = gve_num_tx_queues(priv);
 	switch (stringset) {
 	case ETH_SS_STATS:
-		memcpy(s, *gve_gstrings_main_stats,
-		       sizeof(gve_gstrings_main_stats));
-		s += sizeof(gve_gstrings_main_stats);
-
-		for (i = 0; i < priv->rx_cfg.num_queues; i++) {
-			for (j = 0; j < NUM_GVE_RX_CNTS; j++) {
-				snprintf(s, ETH_GSTRING_LEN,
-					 gve_gstrings_rx_stats[j], i);
-				s += ETH_GSTRING_LEN;
-			}
-		}
+		for (i = 0; i < ARRAY_SIZE(gve_gstrings_main_stats); i++)
+			ethtool_puts(&s, gve_gstrings_main_stats[i]);
 
-		for (i = 0; i < num_tx_queues; i++) {
-			for (j = 0; j < NUM_GVE_TX_CNTS; j++) {
-				snprintf(s, ETH_GSTRING_LEN,
-					 gve_gstrings_tx_stats[j], i);
-				s += ETH_GSTRING_LEN;
-			}
-		}
+		for (i = 0; i < priv->rx_cfg.num_queues; i++)
+			for (j = 0; j < NUM_GVE_RX_CNTS; j++)
+				ethtool_sprintf(&s, gve_gstrings_rx_stats[j],
+						i);
+
+		for (i = 0; i < num_tx_queues; i++)
+			for (j = 0; j < NUM_GVE_TX_CNTS; j++)
+				ethtool_sprintf(&s, gve_gstrings_tx_stats[j],
+						i);
+
+		for (i = 0; i < ARRAY_SIZE(gve_gstrings_adminq_stats); i++)
+			ethtool_puts(&s, gve_gstrings_adminq_stats[i]);
 
-		memcpy(s, *gve_gstrings_adminq_stats,
-		       sizeof(gve_gstrings_adminq_stats));
-		s += sizeof(gve_gstrings_adminq_stats);
 		break;
 
 	case ETH_SS_PRIV_FLAGS:
-		memcpy(s, *gve_gstrings_priv_flags,
-		       sizeof(gve_gstrings_priv_flags));
-		s += sizeof(gve_gstrings_priv_flags);
+		for (i = 0; i < ARRAY_SIZE(gve_gstrings_priv_flags); i++)
+			ethtool_puts(&s, gve_gstrings_priv_flags[i]);
 		break;
 
 	default: