pkcs7_validate_trust
ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);
ret = pkcs7_validate_trust(pkcs7, trusted_keys);
EXPORT_SYMBOL_GPL(pkcs7_validate_trust);
ret = pkcs7_validate_trust(pkcs7, keyring);
extern int pkcs7_validate_trust(struct pkcs7_message *pkcs7,