Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

                                                     ◄Up► ◄Next► ◄Previous►
────────────────────────────────────────────────────────────────────────────
 
include vmm.inc
 
VMMcall _Allocate_GDT_Selector, <DescDWORD1, DescDWORD2, flags>
 
mov     ecx, eax                    ; zero in eax and edx if error
or      ecx, edx
jz      error
 
mov     [Selector], eax             ; new selector
mov     word ptr [GDTSel], dx       ; selector for the GDT
ror     edx, 10h
mov     word ptr [SelCount], dx     ; number of selectors in GDT
 
The _Allocate_GDT_Selector service creates a new selector and adds it to the
Global Descriptor Table (GDT).
 
Parameter   Description
────────────────────────────────────────────────────────────────────────────
 
DescDWORD1  Specifies the high doubleword of the descriptor for the
            selector. This parameter contains the high 16 bits of the base
            address, the high 4 bits of the limit, and the status and type
            bits.
 
DescDWORD2  Specifies the low doubleword of the descriptor for the selector.
            This parameter contains the low 16 bits of the base address and
            limit.
 
flags       Specifies the operation flags. This parameter must be set to 0.
 
Return Value
 
If the service is successful, the EAX and EDX registers contain the
following values:
 
Register  Description
────────────────────────────────────────────────────────────────────────────
EAX       Contains the new selector.
 
EDX       Contains the selector for and the size of the global descriptor
          table (GDT). The low 16 bits contains the selector for the GDT,
          and the high 16 bits contains the size of the GDT expressed as the
          number of selectors in the table.
 
If an error occurs, such as an invalid descriptor value or the GDT is full,
the EAX and EDX registers contain zero to indicate an error.
 
Comments
 
Although this service returns the selector for the GDT, virtual devices
should not attempt to edit the GDT directly. Virtual devices can instead use
the _SetDescriptor service to change selectors in the GDT.
 
Virtual devices should use the BuildDescriptorDWORDs service to set the
DescDWORD1 and DescDWORD2 parameters to the appropriate values.
 
This service sets the RPL of the selector to the DPL of the selector set in
the DescDWORD1 parameter.
 
Uses
 
EAX, EDX
 
See Also
 
_Allocate_LDT_Selector, _Free_GDT_Selector
 
 
                                      ♦