I'm looking for a film I saw a few years ago and can't remember any names or actors in it. It's a chinese kung fu film from around the 80s or older, about a guy who gets captured by a master who always wears a white mask which covers his whole face. He controls the guy with long strings attacked to him so he can stop him from escaping. The master makes the guy train insanely hard at kung fu whilst still attached by strings. There's other parts to the plot but I can't remember. I do remember the fight scene towards the end between the main guy and the master and there's knives involved. This film seems rare and I'm pretty sure there's no big name actors in it.