bpf: Pass const struct bpf_prog * to .check_member

The .check_member field of struct bpf_struct_ops is currently passed the
member's btf_type via const struct btf_type *t, and a const struct
btf_member *member. This allows the struct_ops implementation to check
whether e.g. an ops is supported, but it would be useful to also enforce
that the struct_ops prog being loaded for that member has other
qualities, like being sleepable (or not). This patch therefore updates
the .check_member() callback to also take a const struct bpf_prog *prog
argument.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230125164735.785732-4-void@manifault.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf.h

@@ -1422,7 +1422,8 @@ struct bpf_struct_ops {
 	const struct bpf_verifier_ops *verifier_ops;
 	int (*init)(struct btf *btf);
 	int (*check_member)(const struct btf_type *t,
-			    const struct btf_member *member);
+			    const struct btf_member *member,
+			    const struct bpf_prog *prog);
 	int (*init_member)(const struct btf_type *t,
 			   const struct btf_member *member,
 			   void *kdata, const void *udata);

kernel/bpf/verifier.c

@@ -16792,7 +16792,7 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
 	}
 
 	if (st_ops->check_member) {
-		int err = st_ops->check_member(t, member);
+		int err = st_ops->check_member(t, member, prog);
 
 		if (err) {
 			verbose(env, "attach to unsupported member %s of struct %s\n",

net/ipv4/bpf_tcp_ca.c

@@ -248,7 +248,8 @@ static int bpf_tcp_ca_init_member(const struct btf_type *t,
 }
 
 static int bpf_tcp_ca_check_member(const struct btf_type *t,
-				   const struct btf_member *member)
+				   const struct btf_member *member,
+				   const struct bpf_prog *prog)
 {
 	if (is_unsupported(__btf_member_bit_offset(t, member) / 8))
 		return -ENOTSUPP;