Processes can now wait on signals/children/time. There is no clock
currently so "time" is just a monotonically increating tick count. Added
a SLEEP syscall to test this waiting/waking.
The syscall/sysret instructions don't swap stacks. This was bad but
passable until syscalls caused the scheduler to run, and scheduling a
task that paused due to interrupt.
Adding a new (hopefully temporary) syscall interrupt `int 0xee` to allow
me to test syscalls without stack issues before I tackle the
syscall/sysret issue.
Also implemented a basic `pause` syscall that causes the calling process
to become unready. Because nothing can wake a process yet, it never
returns.
- Scheduler now has multiple linked_lists of processes at different
priorities
- Process structure improvements
- scheduler::tick() and scheduler::schedule() separation
Now any initrd file is treated like a program image and passed to the
loader to load as a process. Very rudimentary elf loading just allocates
pages, copies sections, and sets the ELF's entrypoint as the RIP to
iretq to.
