Here is tagged mbi proposal rebased for multiboot2. I defined begining
of tag buffer as starting with total mbi size to make relocation and
memory mapping trivial.
Current problems:
- I haven't migrated the a.out (as oppose to multiboot kludge) symbols,
drives table and ROM configuration table. I'm not familiar with these
fields. What are they used for?
-Memory usage.  Additionally to the space occupied by payload multiboot
specification uses memory for mbi, ELF sections and modules. Moving all
this information around without overwriting may be a difficult task.
Possible alternatives:
  - Put modules and sections in mbi. But then one-chunk mbi may not find
enough available space in the memory
  - Add a map of memory used by multiboot separately from memory map. I
don't think it's worth it since this information is easily available by
    traversing mbi anyway.
  - Add requirements on position of modules. It actually just moves
complexity from payload to bootloader. (for grub I wrote newreloc layer
for such requirements present in different protocols, it's currently in
late alpha, available at people/phcoder/newreloc)
  - Leave it as is and propose some code to do moving mbi around sanely
under non-copyleft license.


-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko