Map Conventional Memory in Memory Block

Aliases linear  addresses below the 1 MB boundary onto the
linear addresses of a memory block previously allocated with
Int 31H Fn  0504H.

Call With:

   AX     = 0509H
   ESI    = memory block handle
   EBX    = offset within memory block of page(s) to be
           mapped (must be page-aligned)
   ECX    = number of pages to map
   EDX    = linear address of conventional memory (must be
           page-aligned)

Returns:

   if function successful
   Carry flag= clear

   if function unsuccessful
   Carry flag= set
   AX     = error code
           8001H   unsupported function (Conventional Memory
                   Mapping Capability not supported)
           8003H   system integrity (invalid conventional
                   memory address)
           8023H   invalid handle (in ESI)
           8025H   invalid linear address (specified range
                   is not within specified block, or EBX/EDX
                   is not page aligned)

Notes:

o  16-bit DPMI hosts will not support this function.  A
   16-bit client of a 32-bit DPMI 1.0 host can use this
   function.
o  Support of this call by 32-bit DPMI hosts is optional.
   Application programs or DOS Extenders which require this
   call in order to run are not DPMI Compliant.
o  Any committed or mapped pages resided in the linear
   address range that is being mapped into will be
   uncommitted or unmapped automatically by the host.
o  A client may only map conventional memory that it already
   owns; i.e. memory which the client previously allocated
   with Int 31H Fn 0100H or by calling DOS's Int 21H
   Function 48H directly via the translation services.
o  All pages created by this call have the mapped bit (bit
   2) set in the attributes returned by the Get Page
   Attributes function (Int 31H Fn 0506H).
o  DPMI hosts that do not implement virtual memory can
   support this function by simply copying page table
   entries.  The entries must be marked as mapped so that
   the host knows not to free up those physical pages when
   the memory block is freed.
o  DPMI hosts that provide virtual memory must implement
   some form of page aliasing in order to support this
   function.
o  The function can provide a large contiguous memory space
   without virtual memory support.

§  Implementors of DPMI hosts which do not provide virtual
   memory are encouraged to support this function.  Without
   this function, conventional memory may be inaccessible to
   a 32-bit nonsegmented client, because the client may need
   contiguous linear memory for its code and data.  32-bit
   clients can always guarantee that conventional memory is
   not wasted with the following strategy:

§  Call DOS to allocate any free conventional memory
§  If the DPMI host supports virtual memory, call the Mark
   Real Mode Region Pageable function (Int 31H Function
   0602H) to ensure that the host has not locked down
   conventional memory.
§  If the host does not support virtual memory but supports
   the Map Conventional Memory function (Int 31H Function
   0509H), allocate a memory block with uncommitted pages,
   then use Function 0509H to make the physical memory
   allocated below 640 KB addressable in the memory block,
   and therefore useable by the 32-bit application program.