Stay overnight on the Great Wall

I don't think it works, since the great wall sections open for tourists like Badaling, Mutianyu, Jinshanling all have special staff working there who will let all the visitors out at the closing time, and for those unopened sections, it is really dangerous to stay in a tent overnight on the walls. Thus, you have to stay in the farmhouses or hotels at the foot of the great walls. Have a nice trip in China!