Daniel Verkamp: COMBOOT Support

• 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!

3876fad11e9f4ba3d8319eaadffce7c30aaaeaa6 , bcb1ffca2899973f73381d36cdae88e7c13c0881 , 32030bd5f16208b01441eed8ef0d101362770ef0 , 8f4adae9cb357b8f88beea16439fa2afdcc127d3 , f7a3b956e3eaa5689da98721d1bbb55910b5d6c1

• 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