net, xdp: decouple XDP code from the core networking code

Currently, there are a couple of rather big pieces of purely XDP
code residing in `net/core/dev.c` and `net/core/filter.c`, and they
won't get smaller any time soon.
To make it more scalable, move them to the new separate files inside
`net/bpf/`, which is almost empty now, along with `net/core/xdp.c`.
This goes so well so that we only had to make 3 functions global
which were static previously (+1 static key). The only mentions of
XDP left in `filter.c` are helpers which share code with the skb
variants and it would cost much more to make the shared code global
instead.

Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>

MAINTAINERS

@@ -21726,7 +21726,9 @@ F:	include/net/xdp_priv.h
 F:	include/trace/events/xdp.h
 F:	kernel/bpf/cpumap.c
 F:	kernel/bpf/devmap.c
-F:	net/core/xdp.c
+F:	net/bpf/core.c
+F:	net/bpf/dev.c
+F:	net/bpf/prog_ops.c
 F:	samples/bpf/xdp*
 F:	tools/testing/selftests/bpf/*xdp*
 F:	tools/testing/selftests/bpf/*/*xdp*

include/linux/filter.h

@@ -992,6 +992,8 @@ void xdp_do_flush(void);
 #define xdp_do_flush_map xdp_do_flush
 
 void bpf_warn_invalid_xdp_action(struct net_device *dev, struct bpf_prog *prog, u32 act);
+const struct bpf_func_proto *xdp_inet_func_proto(enum bpf_func_id func_id);
+bool xdp_helper_changes_pkt_data(const void *func);
 
 #ifdef CONFIG_INET
 struct sock *bpf_run_sk_reuseport(struct sock_reuseport *reuse, struct sock *sk,

include/linux/netdevice.h

@@ -3848,7 +3848,12 @@ struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *d
 struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 				    struct netdev_queue *txq, int *ret);
 
+DECLARE_STATIC_KEY_FALSE(generic_xdp_needed_key);
+
 int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
+int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
+		      int fd, int expected_fd, u32 flags);
+void dev_xdp_uninstall(struct net_device *dev);
 u8 dev_xdp_prog_count(struct net_device *dev);
 u32 dev_xdp_prog_id(struct net_device *dev, enum bpf_xdp_mode mode);
 

net/bpf/Makefile

@@ -1,5 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-only
-obj-$(CONFIG_BPF_SYSCALL)	:= test_run.o
+
+obj-y				:= core.o dev.o prog_ops.o
+
+obj-$(CONFIG_BPF_SYSCALL)	+= test_run.o
 ifeq ($(CONFIG_BPF_JIT),y)
 obj-$(CONFIG_BPF_SYSCALL)	+= bpf_dummy_struct_ops.o
 endif

net/core/xdp.c → net/bpf/core.c

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
-/* net/core/xdp.c
+/* net/bpf/core.c
  *
  * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
  */