Daniel Verkamp: COMBOOT Support

Journal

Message to soc-mentors discussing implementation details; learned how to get available memory, test if key is hit, call protected-mode code with flat-memory setup, etc.
Finish COMBOOT API “Get Version” - return address of version and copyright strings 4f02100d29583bd9586e4a832eb910f9192d304b
Fill in correct value for available memory field in PSP header c07e41f20e6ef9b89e290733d5c06a8fcadfb0e1

Initial try at COM32 support; helper functions are not implemented yet, so nothing really works 6d18cc20c85e7a1a195705d1da6bd67c0917138f
Wrappers for COM32 helper functions to switch between flat mapping used by COM32 and the virtual address space used by gPXE (COM32 still mainly untested) d5e92f83c8fba51e0a2c803b9204bae7d86c9cd8
Some small fixes to COMBOOT (always load the image in the same place, and use that fact to locate the PSP even if the image changes segment registers) 245547103ed490bfc380d94ea7f7634a6e46f11a

TODO:

Find correct end of available memory value for ESP before executing COM32 images
Finish helper functions (copy between registers and com32sys_t structs)

Find end of memory value from walking memmap and pass it to COM32 programs 164672592936bb3026b4ada3113b3e66f0e6f51c

Fix a lot of small things related to COM32; now hello.c32 and hello2.c32 run correctly!

Only the intcall helper is implemented; the farcall and cfarcall helper functions are still unimplemented, but should be relatively easy now that intcall is working