[9fans] Creating a custom jmp_buf; libthread implementation question

[Joel Salomon <chesky@plan9.jp>]

For my next homework in my Operating Systems class, the professor has
assigned the equivalent of a simple libthread.  I’ve been looking
through the libthread code and getting lost ☹.  I don’t need procs,
only threads (except for the oh-so-fun complication of user-level
pre-emptive scheduling, but I can worry about that mañana).  I do,
however, need to create per-thread stacks, probably by massaging
jmp_bufs in malloc()ed memory.

Where in libthread does the stack get set up, and could somebody
please give me a high-level overview of what the code is doing?

Thanks, --Joel