MIT-6.828-JOS
It's a really good OS course
lab/finished contains code from lab1 to lab6
Most of lab1 to lab5 are completed by myself
Most code of lab6 are copied from petroav, his code has explicit annotation and is easy to read
macfij's repo and Clann24's repo are useful too.
Teacher Shao from HUST has a Chinese Toturial online.
Thanks to them for sharing their code!