net: core: Assert the size of netdev_featres_t

We have about 53 netdev_features_t bits defined and counting, add a
build time check to catch when an u64 type will not be enough and we
will have to convert that to a bitmap. This is done in
register_netdevice() for convenience.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -4108,6 +4108,12 @@ const char *netdev_drivername(const struct net_device *dev);
 
 void linkwatch_run_queue(void);
 
+static inline void netdev_features_size_check(void)
+{
+	BUILD_BUG_ON(sizeof(netdev_features_t) * BITS_PER_BYTE <
+		     NETDEV_FEATURE_COUNT);
+}
+
 static inline netdev_features_t netdev_intersect_features(netdev_features_t f1,
 							  netdev_features_t f2)
 {

net/core/dev.c

@@ -7879,6 +7879,7 @@ int register_netdevice(struct net_device *dev)
 	int ret;
 	struct net *net = dev_net(dev);
 
+	netdev_features_size_check();
 	BUG_ON(dev_boot_phase);
 	ASSERT_RTNL();