plex86 bug

[Kevin Lawton]

I did find a bug, after cosimulating plex86+bochs only a couple thousand
instructions into the boot sequence.  Here's a replacement for a function
in kernel/emulation/access.c.

I implemented a bunch of instructions along the way, and need to
code a bunch more.  I'm also working on booting FreeDOS.  My plan
is a CVS sync by this weekend.  Sorry I haven't got to that.
Might as well start off with a CVS version 0.1.0 that can
run FreeDOS & MSDOS. :^)

-Kevin

  void
write_RMW_virtual(vm_t *vm, void *data, unsigned size)
{
  if (vm->guest_cpu.cr0.fields.pg) {
    if (vm->guest_cpu.address_xlation.pages == 1) {
      write_physical(vm, vm->guest_cpu.address_xlation.paddress1, size, data);
      }
    else {
      write_physical(vm, vm->guest_cpu.address_xlation.paddress1,
                     vm->guest_cpu.address_xlation.len1,
                     data);
      write_physical(vm, vm->guest_cpu.address_xlation.paddress2,
                     vm->guest_cpu.address_xlation.len2,
                     ((Bit8u *) data) + vm->guest_cpu.address_xlation.len1);
      }
    }
  else {
    write_physical(vm, vm->guest_cpu.address_xlation.paddress1, size, data);
    }
}