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The DPMI - DPMI Interface Library
Copyright (c) 1997,98 TMT Development Corp.
All Rights Reserved
INTRODUCTION
------------
The DOS Protected Mode Interface (DPMI) was defined to allow DOS
programs to access the extended memory of PC architecture computers
while maintaining system protection. DPMI defines a specific subset of
DOS and BIOS calls that can be made by protected mode DOS programs. It
also defines a new interface via software interrupt 31h that protected
mode programs use to allocate memory, modify descriptors, call real
mode software, etc. Any operating system that currently supports
virtual DOS sessions should be capable of supporting DPMI without
affecting system security. Some DPMI implementations can execute
multiple protected mode programs in independent virtual machines.
Thus, DPMI applications can behave exactly like any other standard DOS
program and can, for example, run in the background or in a window (if
the environment supports these features). Programs that run in
protected mode also gain all the benefits of virtual memory and can
run in 32-bit flat model if desired.
DPMI PROCEDURES & FUNCTIONS REFERENCE
-------------------------------------
procedure ClearRmRegs (var Regs: TRmRegs)
-----------------------------------------
This procedure clears (fills with zero) the Real Mode registers
structure. You must do it before you call any function, which
uses it! See the TESTLBF.PAS and EXEC16.PAS examples.
function FarGetByte (Seg: Word; Offs: DWord): Byte
--------------------------------------------------
Returns byte value from specified offset of specified
protected mode segment (selector).
function FarGetWord (Seg: Word; Offs: DWord): Word
--------------------------------------------------
Returns word value from specified offset of specified
protected mode segment (selector).
function FarGetDWord (Seg: Word; Offs: DWord): DWord
----------------------------------------------------
Returns dword value from specified offset of specified
protected mode segment (selector).
procedure FarPutByte (Seg: Word; Offs: DWord; Value: Byte)
----------------------------------------------------------
Puts byte value to specified offset of specified
protected mode segment (selector).
procedure FarPutWord (Seg: Word; Offs: DWord; Value: Word)
----------------------------------------------------------
Puts word value to specified offset of specified
protected mode segment (selector).
procedure FarPutDWord (Seg: Word; Offs: DWord; Value: DWord)
------------------------------------------------------------
Puts dword value to specified offset of specified
protected mode segment (selector).
function GetCS: Word
---------------------
Returns current code segment.
function GetDS: Word
---------------------
Returns current data segment.
function AllocateDescriptors (NumberOfDescriptors: Word): Word
--------------------------------------------------------------
This function is used to allocate one or more
descriptors from the task's Local Descriptor Table
(LDT). The descriptor(s) allocated must be initialized
by the application.
Entry: NumberOfDescriptors - Number of descriptors to allocate
Exit: if successful: Base selector (use SelctorInc to asscss to
next selector)
if failed : Zero
function CreateDataDescriptor (Base, Limit: DWord): Word
--------------------------------------------------------
This function is used to allocate one data
descriptor from the task's Local Descriptor Table
(LDT) with specified Base and Limit
Entry: Base - Specified Base
Limit - Specified limit
Exit: if successful: Data Selector
if failed : Zero
function CreateCodeDescriptor (Base, Limit: DWord): Word
--------------------------------------------------------
This function is used to allocate one code
descriptor from the task's Local Descriptor Table
(LDT) with specified Base and Limit
Entry: Base - Specified Base
Limit - Specified limit
Exit: if successful: Code Selector
if failed : Zero
function FreeDescriptor (Selector: Word): Boolean
-------------------------------------------------
This function is used to free descriptors that were
allocated through the Allocate LDT Descriptors
function.
Entry: Selector - selector to free
Exit : if successful: TRUE
if failed : FALSE
function SegmentToDescriptor (Segment: Word): Word
--------------------------------------------------
This function is used to convert real mode segments
into descriptors that are addressable by protected mode
programs.
Entry: Segment - Real mode segment address
Exit : if successful: Selector mapped to real mode segment
if failed : Zero
function SelectorInc: Word
--------------------------
Some functions such as allocate LDT descriptors and
allocate DOS memory can return more than one
descriptor. You must call this function to determine
the value that must be added to a selector to access
the next descriptor in the array.
Entry: None
Exit : if successful: Value to add to get to next selector
if failed : Zero
function GetSegmentBaseAddress (Selsctor: Word): DWord
------------------------------------------------------
This function returns the 32-bit linear base address of
the specified segment.
Entry: Selector - Defined selector
Exit : if successful: 32-bit linear base address of segment
if failed : Zero
function SetSelectorBaseAddress (Selector: Word; Base: DWord): Boolean
----------------------------------------------------------------------
This function changes the 32-bit linear base address of
the specified selector.
Entry: Selector - Defined selector
Base - 32-bit linear base address for segment
Exit : if successful: TRUE
if failed : FALSE
function SetSelectorLimit (Selector: Word; Limit: DWord): Word
--------------------------------------------------------------
This function sets the limit for the specified segment.
Entry: Selector - Defined selector
Limit - 32-bit segment limit
Exit : if successful: Segment
if failed : Zero
function GetSelectorAccessRights (Selector: Word): Word
-------------------------------------------------------
This function returns access rights and type fields of a
descriptor.
Entry: Selector - Defined selector
Rights - 80386 access rights/type word
Exit : if successful: Access rights
if failed: Zero
function SetSelectorAccessRights (Selector,Rights: Word): Boolean
-----------------------------------------------------------------
This function allows a protected mode program to modify
the access rights and type fields of a descriptor.
Entry: Selector - Defined selector
Rights - 80386 access rights/type word
Exit : if successful: TRUE
if failed: FALSE
function CreateCodeAlias (Selector: Word): Word
-----------------------------------------------
This function will create a code descriptor that has
the same base and limit as the specified code segment
descriptor.
Entry: Selector - Data segment selector
Exit : if successful: Alias selector
if failed: Zero
function CreateDataAlias (Selector: Word): Word
-----------------------------------------------
This function will create a code descriptor that has
the same base and limit as the specified code segment
descriptor.
Entry: Selector - Data segment selector
Exit : if successful: Alias selector
if failed: Zero
function GetDescriptor (Selector: Word; var Descriptor: TDescriptor): Boolean
-----------------------------------------------------------------------------
This function copies the descriptor table entry for a
specified descriptor into an eight byte buffer.
Entry: Selector - Defined selector
Descriptor - Pointer to an 8 byte buffer to receive copy
of descriptor
Exit : if successful: TRUE
if failed: FALSE
function SetDescriptor (Selector: Word; var Descriptor: TDescriptor): Boolean
-----------------------------------------------------------------------------
This function copies an eight byte buffer into the LDT
entry for a specified descriptor.
Entry: Selector - Defined selector
Descriptor - Pointer to an 8 byte buffer that contains
descriptor
Exit : if successful: TRUE
if failed: FALSE
function AllocateSpecificDescriptor (Selector: Word): Boolean
-------------------------------------------------------------
This function is used to allocate one specific
LTD descriptor.
Entry: Selector - Selector to allocate
Exit: if successful: TRUE
if failed : FALSE
function AllocDOSmemoryBlock (SizeInBytes: DWord): DWord
--------------------------------------------------------
This function will allocate a block of memory from the
DOS free memory pool. It returns both the real mode
segment and one or more descriptors that can be used by
protected mode applications to access the block.
Entry: SizeInBytes - Number of bytes desired
Exit : if successful: Paragraph-segment value in its high-order
word and a selector in its low-order word
if failed: Zero
function FreeDOSMemoryBlock (Selector: Word): Boolean
-----------------------------------------------------
This function frees memory that was allocated through
the Allocate DOS Memory Block function.
Entry: Selector - Selector of block to free
Exit : if successful: TRUE
if failed: FALSE
function ResizeDOSmemoryBlock (Selector: Word; NewSize: DWord): Boolean
-----------------------------------------------------------------------
This function is used to grow or shrink a memory block
that was allocated through the AllocateDOSmemoryBlock
function.
Entry: NewSize - New block size in bytes
Selector - Selector of block to modify
Exit : if successful: TRUE
if failed: FALSE
function DOSMemoryAlloc (SizeInBytes: DWord): Word
--------------------------------------------------
This function will allocate a block of memory from the
DOS free memory pool. It returns real mode only
segment of alloceted DOS memory block.
Entry: SizeInBytes - Number of bytes desired
Exit : if successful: Paragraph-segment value
if failed: Zero
Note: To get access to allocated DOS memory block you should
multiply the returned Paragrapf-segment by 16 and add _zero value.
Example:
function MkDOSPointer (Segment: Word): Pointer;
begin
Result:=DWord(Segment)*16+_zero;
end.
This function makes a protected mode pointer on a given segment of
allocated DOS memory block.
function DOSMemoryFree (Segment: Word): Boolean
-----------------------------------------------
This function frees memory that was allocated through
the DOSMemoryAlloc function.
Entry: Segment - Real mode segment of block to free
Exit : if successful: TRUE
if failed: FALSE
Remarks:
DOSMemoryAlloc and DOSMemoryFree functions uses Int 21h and do not
require DPMI function 100h, which is not supported by PMODE.EXE
extender. DOSMemoryAlloc and DOSMemoryFree will work correctly in
RAW DOS.
function GetRealModeIntVec (IntNo: Byte; var RSeg,ROfs: Word): Boolean
----------------------------------------------------------------------
This function returns the value of the current task's
real mode interrupt vector for the specified interrupt.
Entry: IntNo - Interrupt number
Exit : if successful: TRUE
RSeg - Segment of real mode interrupt handler
ROfs - Offset of real mode interrupt handler
if failed: FALSE
function SetRealModeIntVec (IntNo: Byte; RSeg,ROfs: Word): Boolean
------------------------------------------------------------------
This function sets the value of the current task's real
mode interrupt vector for the specified interrupt.
Entry: IntNo - Interrupt number
RSeg - Segment of real mode interrupt handler
ROfs - Offset of real mode interrupt handler
Exit : if successful: TRUE
if failed: FALSE
function GetExceptionHandler (ExpFault: Byte; var Sel: Word; var Offs: DWord): Boolean
--------------------------------------------------------------------------------------
This function returns the Pointer to the current
protected mode exception handler for the specified
exception number.
Entry: ExpFault - Exception/fault number (00h-1Fh)
Exit : if successful: TRUE
Sel,Offs: Selector,Offset of exception handler
if failed: FALSE
function SetExceptionHandler (ExpFault: Byte; Sel: Word; Offs: DWord): Boolean
------------------------------------------------------------------------------
This function allows protected mode applications to
intercept processor exceptions that are not handled by
the DPMI environment. Programs may wish to handle
exceptions such as not present segment faults which
would otherwise generate a fatal error.
Entry: ExpFault - Exception/fault number (00h-1Fh)
Sel,Offs - Selector, Offset of exception handler
Exit : if successful: TRUE
if failed: FALSE
function GetDPMIIntVec (IntNo: Byte; var Sel: Word; var Offs: DWord): Boolean
-----------------------------------------------------------------------------
This function returns the ParPointer to the current
protected mode interrupt handler for the specified
interrupt number.
Entry: IntNo - Interrupt number
Exit : if successful: TRUE
Sel,Offs - Selector,Offset of interrupt handler
if failed: FALSE
function SetDPMIIntVec (IntNo: Byte; Sel: Word; Offs: DWord): Boolean
---------------------------------------------------------------------
This function sets the address of the specified
protected mode interrupt vector.
Entry: IntNo - Interrupt number
Addr - Pointer of interrupt handler
Exit : if successful: TRUE
if failed: FALSE
function RealModeInt (IntNo: Byte; var Regs: TRmRegs): Boolean
--------------------------------------------------------------
This function simulates an interrupt in real mode. It
will invoke the CS:IP specified by the real mode
interrupt vector and the handler must return by
executing an iret.
Entry: IntNo - Interrupt number
Regs - TRealRegs structure
Exit : if successful: TRUE
if failed: FALSE
function CallRealModeFar (var Regs: TRmRegs): Boolean
-----------------------------------------------------
This function calls a real mode procedure. The called
procedure must execute a far return when it completes.
Entry: Regs - TRealRegs structure
Exit : if successful: TRUE
if failed: FALSE
function CallRealModeIRet (var Regs: TRmRegs): Boolean
------------------------------------------------------
This function calls a real mode procedure. The called
procedure must execute an iret when it completes.
Entry: Regs - TRealRegs structure
Exit : if successful: TRUE
if failed: FALSE
function AllocRealModeCallBack (HandlerAddr, RegsAddr: Pointer;
var HndSeg: Word; var HndOfs: DWord): Boolean;
-------------------------------------------------------------------
This function is used to obtain a unique real mode
SEG:OFFSET that will transfer control from real mode to
a protected mode procedure.
Entry: Linear address of procedure to call
Linear address of real mode call structure
Exit : if successful: Segment:Offset of real mode call address
if failed: Zero
function FreeRealModeCallBack (HndSeg: Word; HndOfs: DWord): Boolean;
----------------------------------------------------------
This function frees a real mode call-back address that
was allocated through the allocate real mode call-back
address service.
Entry: HndSeg and HndOfs - segment and offset of real mode
call-back address to free
Exit : if successful: TRUE
if failed: FALSE
function GetDPMIVer: Word
-------------------------
Returns the version of DPMI services supported.
Entry: None
Exit : if successful: Version of DPMI service
if failed : Zero
function GetFreeMemoryInfo (BufferPtr: Pointer): Boolean
--------------------------------------------------------
This function is provided so that protected mode
applications can determine how much memory is
available. Under DPMI implementations that support
virtual memory, it is important to consider issues such
as the amount of available physical memory.
Entry: BufferPtr - Selector:Offset of 30h byte buffer
Exit : if successful: TRUE
if failed: FALSE
function MapPhysicalToLinear (PhysAddr, SizeInBytes: DWord): DWord
------------------------------------------------------------------
This function can be used by device
drivers to convert a physical address into a linear address.
The linear address can then be used to access the device
memory.
Entry: PhysAddr - Physical address to map
SizeInBytes - Size in bytes of block to map
Exit : if successful: Pointer to linear address that can be
used to access the physical memory
if failed: Nil
function GetDisableInterruptState: Boolean
------------------------------------------
This function will disable the virtual interrupt flag
and return the previous state of the virtual interrupt
flag.
Entry: None
Exit : Virtual interrupt state
function GetEnableInterruptState: Boolean
-----------------------------------------
This function will enable the virtual interrupt flag
and return the previous state of the virtual interrupt
flag.
Entry: None
Exit : Virtual interrupt state
function GetInterruptState: Boolean
-------------------------------------------------------------------
This function will disable return state of the virtual
interrupt flag.
Entry: None
Exit : Virtual interrupt state