Implement Debugging Functions

[salekinsirajus]

• uint32 free_ffs_pages() – number of free frames in the FFS space (see below)
• uint32 free_swap_pages() – number of free frames in the swap space (see below)
• uint32 allocated_virtual_pages(pid32 pid) – number of virtual pages allocated by a
  particular process (including pages allocated but not mapped to physical memory space)
• uint32 used_ffs_frames(pid32 pid) – number of FFS frames in use by a given process