ekimekim/gbos

A just-for-fun project for approximating an "operating system" for the original Game Boy.

Goals:
	Time-sharing scheduler
	Negotiation of access to shared resources
		eg. vram, audio, input, RAM
	IPC
	task spawning
	sleep()

Stretch goals:
	Text interface application
	Split screen access to vram

Non goals:
	Full state switching (eg. all io regs, vram, ...) to allow 'bare metal' programs to run
	Security - all programs must obey the rules but if they don't we can't stop them


Notes:

'Core' code is the OS itself, is located in ROM0 and uses RAM0. It has a dedicated stack.
'Tasks' (generally) run in an arbitrary ROM bank and may use a RAM bank allocated at runtime.
This allows for limited dynamic memory management without needing to make code relocatable.
There will probably also be 'core tasks' that are tasks that do async core work, and so not all
tasks will have a dedicated ROM bank. Currently design allows for up to one ROM and RAM bank per task.
These banks are only loaded when the task is.
Tasks are in charge of managing their own stack.
TODO allocate some stack space (and other space?) for tasks that don't otherwise need their own RAM bank.

Functions with 'T_' prepended, eg. 'T_Foobar' are suitable for calling 'into' core.
Generally, these don't actually trigger a task switch onto the core stack, but do some core-managed job
on the task's stack before returning, ie. they're normal functions, just semantically seperated
as being allowed to touch core stuff.