* The semantics of the join system call should change so that it only
returns the exit code once.
+
+* mmap/munmap should use segment IDs like Nachos. Too hard otherwise.
+
+* Some confusion--do we really get overlapping ro/rw segment in normal
+ link? Student example seemed to show that we don't.
+
+* Add qsort(), bsearch() implementations to kernel.
+
+* Finish writing the tour.
+
+* Come up with a way for us to release some of the tests.
+
+* userprog project should mark read-only pages as actually read-only
+ in the page table