bpf: Migrate cgroup_bpf to internal cgroup_bpf_attach_type enum

Add an enum (cgroup_bpf_attach_type) containing only valid cgroup_bpf
attach types and a function to map bpf_attach_type values to the new
enum. Inspired by netns_bpf_attach_type.

Then, migrate cgroup_bpf to use cgroup_bpf_attach_type wherever
possible.  Functionality is unchanged as attach_type_to_prog_type
switches in bpf/syscall.c were preventing non-cgroup programs from
making use of the invalid cgroup_bpf array slots.

As a result struct cgroup_bpf uses 504 fewer bytes relative to when its
arrays were sized using MAX_BPF_ATTACH_TYPE.

bpf_cgroup_storage is notably not migrated as struct
bpf_cgroup_storage_key is part of uapi and contains a bpf_attach_type
member which is not meant to be opaque. Similarly, bpf_cgroup_link
continues to report its bpf_attach_type member to userspace via fdinfo
and bpf_link_info.

To ease disambiguation, bpf_attach_type variables are renamed from
'type' to 'atype' when changed to cgroup_bpf_attach_type.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210819092420.1984861-2-davemarchevsky@fb.com

include/uapi/linux/bpf.h

@@ -84,7 +84,7 @@ struct bpf_lpm_trie_key {
 
 struct bpf_cgroup_storage_key {
 	__u64	cgroup_inode_id;	/* cgroup inode id */
-	__u32	attach_type;		/* program attach type */
+	__u32	attach_type;		/* program attach type (enum bpf_attach_type) */
 };
 
 union bpf_iter_link_info {

net/ipv4/af_inet.c

@@ -452,7 +452,7 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 	 * changes context in a wrong way it will be caught.
 	 */
 	err = BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr,
-						 BPF_CGROUP_INET4_BIND, &flags);
+						 CGROUP_INET4_BIND, &flags);
 	if (err)
 		return err;
 
@@ -781,7 +781,7 @@ int inet_getname(struct socket *sock, struct sockaddr *uaddr,
 		sin->sin_port = inet->inet_dport;
 		sin->sin_addr.s_addr = inet->inet_daddr;
 		BPF_CGROUP_RUN_SA_PROG_LOCK(sk, (struct sockaddr *)sin,
-					    BPF_CGROUP_INET4_GETPEERNAME,
+					    CGROUP_INET4_GETPEERNAME,
 					    NULL);
 	} else {
 		__be32 addr = inet->inet_rcv_saddr;
@@ -790,7 +790,7 @@ int inet_getname(struct socket *sock, struct sockaddr *uaddr,
 		sin->sin_port = inet->inet_sport;
 		sin->sin_addr.s_addr = addr;
 		BPF_CGROUP_RUN_SA_PROG_LOCK(sk, (struct sockaddr *)sin,
-					    BPF_CGROUP_INET4_GETSOCKNAME,
+					    CGROUP_INET4_GETSOCKNAME,
 					    NULL);
 	}
 	memset(sin->sin_zero, 0, sizeof(sin->sin_zero));

net/ipv4/udp.c

@@ -1143,7 +1143,7 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		rcu_read_unlock();
 	}
 
-	if (cgroup_bpf_enabled(BPF_CGROUP_UDP4_SENDMSG) && !connected) {
+	if (cgroup_bpf_enabled(CGROUP_UDP4_SENDMSG) && !connected) {
 		err = BPF_CGROUP_RUN_PROG_UDP4_SENDMSG_LOCK(sk,
 					    (struct sockaddr *)usin, &ipc.addr);
 		if (err)

net/ipv6/af_inet6.c

@@ -455,7 +455,7 @@ int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 	 * changes context in a wrong way it will be caught.
 	 */
 	err = BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr,
-						 BPF_CGROUP_INET6_BIND, &flags);
+						 CGROUP_INET6_BIND, &flags);
 	if (err)
 		return err;
 
@@ -532,7 +532,7 @@ int inet6_getname(struct socket *sock, struct sockaddr *uaddr,
 		if (np->sndflow)
 			sin->sin6_flowinfo = np->flow_label;
 		BPF_CGROUP_RUN_SA_PROG_LOCK(sk, (struct sockaddr *)sin,
-					    BPF_CGROUP_INET6_GETPEERNAME,
+					    CGROUP_INET6_GETPEERNAME,
 					    NULL);
 	} else {
 		if (ipv6_addr_any(&sk->sk_v6_rcv_saddr))
@@ -541,7 +541,7 @@ int inet6_getname(struct socket *sock, struct sockaddr *uaddr,
 			sin->sin6_addr = sk->sk_v6_rcv_saddr;
 		sin->sin6_port = inet->inet_sport;
 		BPF_CGROUP_RUN_SA_PROG_LOCK(sk, (struct sockaddr *)sin,
-					    BPF_CGROUP_INET6_GETSOCKNAME,
+					    CGROUP_INET6_GETSOCKNAME,
 					    NULL);
 	}
 	sin->sin6_scope_id = ipv6_iface_scope_id(&sin->sin6_addr,

net/ipv6/udp.c

@@ -1475,7 +1475,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		fl6.saddr = np->saddr;
 	fl6.fl6_sport = inet->inet_sport;
 
-	if (cgroup_bpf_enabled(BPF_CGROUP_UDP6_SENDMSG) && !connected) {
+	if (cgroup_bpf_enabled(CGROUP_UDP6_SENDMSG) && !connected) {
 		err = BPF_CGROUP_RUN_PROG_UDP6_SENDMSG_LOCK(sk,
 					   (struct sockaddr *)sin6, &fl6.saddr);
 		if (err)

tools/include/uapi/linux/bpf.h

@@ -84,7 +84,7 @@ struct bpf_lpm_trie_key {
 
 struct bpf_cgroup_storage_key {
 	__u64	cgroup_inode_id;	/* cgroup inode id */
-	__u32	attach_type;		/* program attach type */
+	__u32	attach_type;		/* program attach type (enum bpf_attach_type) */
 };
 
 union bpf_iter_link_info {