bpf: Replace open code with for allocated object check

>From commit 282de143 ("bpf: Introduce allocated objects support"),
With this allocated object with BPF program, (PTR_TO_BTF_ID | MEM_ALLOC)
has been a way of indicating to check the type is the allocated object.

commit d8939cb0 ("bpf: Loosen alloc obj test in verifier's
reg_btf_record")
>From the commit, there has been helper function for checking this, named
type_is_ptr_alloc_obj(). But still, some of the code use open code to
retrieve this info. This commit replaces the open code with the
type_is_alloc(), and the type_is_ptr_alloc_obj() function.
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230527122706.59315-1-danieltimlee@gmail.com

kernel/bpf/verifier.c

@@ -5894,7 +5894,7 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
 		 * program allocated objects (which always have ref_obj_id > 0),
 		 * but not for untrusted PTR_TO_BTF_ID | MEM_ALLOC.
 		 */
-		if (atype != BPF_READ && reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) {
+		if (atype != BPF_READ && !type_is_ptr_alloc_obj(reg->type)) {
 			verbose(env, "only read is supported\n");
 			return -EACCES;
 		}
@@ -7514,7 +7514,7 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 	if (base_type(arg_type) == ARG_PTR_TO_MEM)
 		type &= ~DYNPTR_TYPE_FLAG_MASK;
 
-	if (meta->func_id == BPF_FUNC_kptr_xchg && type & MEM_ALLOC)
+	if (meta->func_id == BPF_FUNC_kptr_xchg && type_is_alloc(type))
 		type &= ~MEM_ALLOC;
 
 	for (i = 0; i < ARRAY_SIZE(compatible->types); i++) {