netdevsim: don't compile BPF code if syscall not enabled

We should not compile netdevsim/bpf.c if BPF syscall is not
enabled.  Otherwise bpf core would have to provide wrappers
for all functions offload drivers may call, even though
system will never see a BPF object.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netdevsim/Makefile

@@ -4,4 +4,8 @@ obj-$(CONFIG_NETDEVSIM) += netdevsim.o
 
 netdevsim-objs := \
 	netdev.o \
-	bpf.o \
+
+ifeq ($(CONFIG_BPF_SYSCALL),y)
+netdevsim-objs += \
+	bpf.o
+endif

drivers/net/netdevsim/netdevsim.h

@@ -68,12 +68,40 @@ struct netdevsim {
 
 extern struct dentry *nsim_ddir;
 
+#ifdef CONFIG_BPF_SYSCALL
 int nsim_bpf_init(struct netdevsim *ns);
 void nsim_bpf_uninit(struct netdevsim *ns);
 int nsim_bpf(struct net_device *dev, struct netdev_bpf *bpf);
 int nsim_bpf_disable_tc(struct netdevsim *ns);
 int nsim_bpf_setup_tc_block_cb(enum tc_setup_type type,
 			       void *type_data, void *cb_priv);
+#else
+static inline int nsim_bpf_init(struct netdevsim *ns)
+{
+	return 0;
+}
+
+static inline void nsim_bpf_uninit(struct netdevsim *ns)
+{
+}
+
+static inline int nsim_bpf(struct net_device *dev, struct netdev_bpf *bpf)
+{
+	return bpf->command == XDP_QUERY_PROG ? 0 : -EOPNOTSUPP;
+}
+
+static inline int nsim_bpf_disable_tc(struct netdevsim *ns)
+{
+	return 0;
+}
+
+static inline int
+nsim_bpf_setup_tc_block_cb(enum tc_setup_type type, void *type_data,
+			   void *cb_priv)
+{
+	return -EOPNOTSUPP;
+}
+#endif
 
 static inline struct netdevsim *to_nsim(struct device *ptr)
 {