This commit makes several fundamental changes to memory handling:
- the frame allocator is now only an allocator for free frames, and does
not track used frames.
- the frame allocator now stores its free list inside the free frames
themselves, as a hybrid stack/span model.
- This has the implication that all frames must currently fit within
the offset area.
- kutil has a new allocator interface, which is the only allowed way for
any code outside of src/kernel to allocate. Code under src/kernel
_may_ use new/delete, but should prefer the allocator interface.
- the heap manager has become heap_allocator, which is merely an
implementation of kutil::allocator which doles out sections of a given
address range.
- the heap manager now only writes block headers when necessary,
avoiding page faults until they're actually needed
- page_manager now has a page fault handler, which checks with the
address_manager to see if the address is known, and provides a frame
mapping if it is, allowing heap manager to work with its entire
address size from the start. (Currently 32GiB.)
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