I forgot to account for tracking page table physical addresses, so
this is a bit of an overhaul. Major changes:
- Refactor bootstrap code into more functions and:
- Only allocate 32 pages of scratch space
- Remap remaining space into top 256GiB, the "page table space"
- Use the page table space to directly offset-map page table pages
from their physical addresses, to avoid tracking overhead.
- Refactor page_block list functions into static functions to better
handle null/empty lists
Return to having the bootloader re-map the kernel into the higher
half before jumping into the kernel entrypoint, so we don't have
to juggle pointers inside the kernel.
Map is still identity-mapped. I think we need to sort and/or clean up
the map before using a higher half address. In-kernel vga output not
working yet, but do_the_set_registers() is getting called.
