Exit Visa Stamps from mainland china

I have an entry stamp going into mainland given at the Shanghai airport. Before 60 days I must leave mainland and have my passport stamped.

If I fly from Wuhan Airport to Hong Kong Airport, how would I get the exit stamp from mainland, since Wuhan does not have a passport control station?

Any suggestions? Basically, want to renew the entry and exit stamps for another 60 day stay in mainland.

Thanks!