Source file origins:

threads/loader.S: From MIT class code but heavily modified.
threads/mmu.h: Ditto.
threads/io.h: Also from MIT class code but less modified.

threads/synch.c: More or less transliterated from Nachos' synch.cc.
filesys/filesys.c: Ditto.
filesys/filehdr.c: Ditto.

All other files written by me, although inspiration is often due to
Nachos or in some cases Linux.