File descriptor accounting

[zmitchell]

It would be convenient if proctrace could keep track of which file descriptors were open at which points in time, including which ones were inherited via a fork.

Monitoring open and close syscalls is pretty straightforward, but determining which fds were inherited is less straightforward.
I think you find the file table through the $cur_task builtin variable, but it seems like in the actual kernel you're supposed to do this while holding some kind of lock, and we don't have that lock.