bpf: Provide function to get vmlinux BTF information

It will be used later for BPF structure display support
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/1601292670-1616-2-git-send-email-alan.maguire@oracle.com

include/linux/bpf.h

@@ -1364,6 +1364,8 @@ int bpf_check(struct bpf_prog **fp, union bpf_attr *attr,
 	      union bpf_attr __user *uattr);
 void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
 
+struct btf *bpf_get_btf_vmlinux(void);
+
 /* Map specifics */
 struct xdp_buff;
 struct sk_buff;

kernel/bpf/verifier.c

@@ -11533,6 +11533,17 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 	return 0;
 }
 
+struct btf *bpf_get_btf_vmlinux(void)
+{
+	if (!btf_vmlinux && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
+		mutex_lock(&bpf_verifier_lock);
+		if (!btf_vmlinux)
+			btf_vmlinux = btf_parse_vmlinux();
+		mutex_unlock(&bpf_verifier_lock);
+	}
+	return btf_vmlinux;
+}
+
 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
 	      union bpf_attr __user *uattr)
 {
@@ -11566,12 +11577,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
 	env->ops = bpf_verifier_ops[env->prog->type];
 	is_priv = bpf_capable();
 
-	if (!btf_vmlinux && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
-		mutex_lock(&bpf_verifier_lock);
-		if (!btf_vmlinux)
-			btf_vmlinux = btf_parse_vmlinux();
-		mutex_unlock(&bpf_verifier_lock);
-	}
+	bpf_get_btf_vmlinux();
 
 	/* grab the mutex to protect few globals used by verifier */
 	if (!is_priv)