bpf: Make internal bpf API independent of CONFIG_BPF_SYSCALL #ifdefs

Socket filter code and other subsystems with upcoming eBPF
support should not need to deal with the fact that we have
CONFIG_BPF_SYSCALL defined or not.

Having the bpf syscall as a config option is a nice thing and
I'd expect it to stay that way for expert users (I presume one
day the default setting of it might change, though), but code
making use of it should not care if it's actually enabled or
not.

Instead, hide this via header files and let the rest deal with it.

Signed-off-by: Daniel Borkmann <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Reviewed-by: Masami Hiramatsu <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

include/linux/bpf.h

···
 	enum bpf_prog_type type;
 };
 
-void bpf_register_prog_type(struct bpf_prog_type_list *tl);
-
 struct bpf_prog;
 
 struct bpf_prog_aux {
···
 };
 
 #ifdef CONFIG_BPF_SYSCALL
+void bpf_register_prog_type(struct bpf_prog_type_list *tl);
+
 void bpf_prog_put(struct bpf_prog *prog);
-#else
-static inline void bpf_prog_put(struct bpf_prog *prog) {}
-#endif
 struct bpf_prog *bpf_prog_get(u32 ufd);
+#else
+static inline void bpf_register_prog_type(struct bpf_prog_type_list *tl)
+{
+}
+
+static inline struct bpf_prog *bpf_prog_get(u32 ufd)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
+static inline void bpf_prog_put(struct bpf_prog *prog)
+{
+}
+#endif
+
 /* verify correctness of eBPF program */
 int bpf_check(struct bpf_prog *fp, union bpf_attr *attr);