[RFC bpf-next v2 1/9] bpf: add a get_helper_proto() utility function

[Eduard Zingerman <eddyz87@gmail.com>]

Extract the part of check_helper_call() as a utility function allowing
to query 'struct bpf_func_proto' for a specific helper function id.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/verifier.c | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d3927d819465..4869f1fb0a42 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10261,6 +10261,24 @@ static void update_loop_inline_state(struct bpf_verifier_env *env, u32 subprogno
 				 state->callback_subprogno == subprogno);
 }
 
+static int get_helper_proto(struct bpf_verifier_env *env, int func_id,
+			    const struct bpf_func_proto **ptr)
+{
+	const struct bpf_func_proto *result = NULL;
+
+	if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID)
+		return -ERANGE;
+
+	if (env->ops->get_func_proto)
+		result = env->ops->get_func_proto(func_id, env->prog);
+
+	if (!result)
+		return -EINVAL;
+
+	*ptr = result;
+	return 0;
+}
+
 static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			     int *insn_idx_p)
 {
@@ -10277,18 +10295,16 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 
 	/* find function prototype */
 	func_id = insn->imm;
-	if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
-		verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
-			func_id);
+	err = get_helper_proto(env, insn->imm, &fn);
+	if (err == -ERANGE) {
+		verbose(env, "invalid func %s#%d\n", func_id_name(func_id), func_id);
 		return -EINVAL;
 	}
 
-	if (env->ops->get_func_proto)
-		fn = env->ops->get_func_proto(func_id, env->prog);
-	if (!fn) {
+	if (err) {
 		verbose(env, "program of this type cannot use helper %s#%d\n",
 			func_id_name(func_id), func_id);
-		return -EINVAL;
+		return err;
 	}
 
 	/* eBPF programs must be GPL compatible to use GPL-ed functions */
-- 
2.45.2