Detroit (USA) -> Toronto (Canada) -> Shanghai -> Hong Kong, Direct Transits

My itinerary from Detroit (USA) to Hong Kong passes through Toronto and Shanghai (or alternatively Beijing), by Air Canada and Cathay Pacific. The scheduled layover in Shanghai is 2.5 hours. I have no plans to leave the secure area of the airport. Is that enough time to make the connection? Can I go directly from gate to gate, or will I need to pass through any security or immigration checks? Thank you.