The World of Computer Software/World_Of_Computer_Software-02-385-Vol-1of3.iso/m/msc7.zip/DPMI.ASM

Assembly Source File | 1992-02-17 | 69KB | 2,845 lines

;;  Copyright (c) 1992, Qualitas, Inc.  All Rights Reserved
;;
;;  dpmi.asm - Source code for Qualitas DPMI library
;;

    include dpmi.inc

    .286p
    .model SMALL, C

    .data

;; data required by fix-up routines

codePara    dw    ?
dataPara    dw    ?
fixupSel    dw    ?
previous21    dd    ?

    .code

;;======================================================================
;; Function: Release Time Slice
;;
;; Synopsis:
;;
;;    void DPMIReleaseTimeSlice(void);
;;
;; Description:
;;
;;    DPMI clients call this function to indicate an idle state to the
;;    DPMI host.  This enables multitasking DPMI hosts to schedule other
;;    clients. Installing this call inside idle loops can result in
;;    significant improvement of system throughput.
;;
;; DPMI reference: INT 2Fh AX=1680h

DPMIReleaseTimeSlice PROC C
    mov    ax, 1680h
    int    2fh
    ret
DPMIReleaseTimeSlice ENDP

;;======================================================================
;; Function: Get CPU Mode
;;
;; Synopsis:
;;
;;    int DPMIGetCPUMode(void);
;;
;; Description:
;;
;;    This function may be used by mode sensitive applications to determine
;;    the current processor operating mode. Clients must verify the
;;    presence of a DPMI host prior to making this call. The function
;;    returns zero if executing in protected mode, and returns non-zero
;;    if running in real or virtual 86 mode.
;;
;; DPMI reference: INT 2Fh AX=1686h

DPMIGetCPUMode PROC C
    mov    ax, 1686h
    int    2Fh
    ret
DPMIGetCPUMode ENDP

;;======================================================================
;; Function: Obtain Mode Switch Entry Point
;;
;; Synopsis:
;;
;;    int DPMIObtainSwitchEntryPoint(
;;        uShort *flags,            ;; 32-bitness flag
;;        uChar *processor,        ;; processor type
;;        uChar *majorVersion,        ;; major version #
;;        uChar *minorVersion,        ;; minor version #
;;        uShort *nPrivateDataParas,    ;; size of host data
;;        void (far* *entryAddress)());    ;; switch entry point
;;
;; Description:
;;
;;    This call determines if a DPMI host is present, and if so, returns
;;    necessary information on how to invoke it.  The function returns
;;    zero if a DPMI host was found; otherwise it returns non-zero.
;;
;;    All arguments are pointers to locations to store return values.
;;    The flags argument is non-zero if the DPMI host supports 32-bit
;;    applications.  The processor argument is written as 2 (80286),
;;    3 (80386), 4 (80486), or 5 (future). The version arguments indicate
;;    the version numbers of the DPMI host (For DPMI 0.9, major version is
;;    zero, and minor version is 90).  The nPrivateDataParas argument
;;    receives the number of paragraphs of memory that the host requires
;;    for each client.  If this is non-zero, the client must provide
;;    this much memory prior to calling the mode switch entry point, and
;;    the memory must be paragraph aligned.
;;
;;    The value written at the entryAddress argument is the far address
;;    to call to make the initial switch into protected mode. See also,
;;    DPMIEnterProtectedMode.
;;
;; DPMI reference: INT 2Fh AX=1687h

DPMIObtainSwitchEntryPoint PROC C USES SI DI,    \
    flags:PTR,        \
    processor:PTR,        \
    majorVersion:PTR,    \
    minorVersion:PTR,    \
    nPrivateDataParas:PTR,    \
    entryAddress:PTR

    mov    ax, 1687h        ; test for presence of DPMI host
    int    2Fh

    or    ax, ax            ; ax == 0 means host responded
    jnz    noHost

    mov    ax, bx            ; save flags in ax

    ldptr    bx, flags
    mov    [bx], ax
    ldptr    bx, processor
    mov    [bx], cl
    ldptr    bx, majorVersion
    mov    [bx], dh
    ldptr    bx, minorVersion
    mov    [bx], dl
    ldptr    bx, nPrivateDataParas
    mov    [bx], si
    ldptr    bx, entryAddress
    mov    [bx], di
    mov    [bx+2], es

    xor    ax, ax
noHost:
    ret
DPMIObtainSwitchEntryPoint ENDP

;;======================================================================
;; Function: Enter Protected Mode
;;
;; Synopsis:
;;
;;    int DPMIEnterProtectedMode(
;;        void (far *switchEntryPoint)(),    ;; mode switch entry point
;;        uShort bitness,            ;; 16 or 32
;;        uShort nPrivateDataParas);    ;; number of paras required
;;
;;
;; Description:
;;
;;    This function is used to make the initial switch into protected
;;    mode.  The switchEntryPoint argument is the value returned in the
;;    entryAddress argument of ObtainSwitchEntryPoint.  The bitness argument
;;    is zero to indicate that the calling client is 16-bit, and is one to
;;    indicate that the calling client is 32-bit.  The nPrivateDataParas
;;    argument is obtained from the function DPMIObtainSwitchEntryPoint.
;;
;;    If the call returns zero, the client is then running in protected
;;    mode.  The segment registers CS, DS, and SS contain selectors that
;;    address the same linear memory as they did in real mode at the
;;    time of the call.  The selector in ES addresses the programs PSP,
;;    and the corresponding descriptor has a limit of 0xFF.  If running
;;    on a 32-bit processor, FS and GS are zero.
;;
;; DPMI reference: calling the mode switch entry point
;;
;; Version 1.0 Error returns:
;;
;;    8011h    descriptor unavailable
;;    8021h    32-bit clients not supported

DPMIEnterProtectedMode PROC C \
    switchEntryPoint:FAR PTR,    \
    bitness:uShort,            \
    nPrivateDataParas:uShort

    mov    ah, 48h            ;; get the required memory block
    mov    bx, nPrivateDataParas
    int    21h
    jc    @@fail

    mov    es, ax            ;; set up and call the mode switch
    mov    ax, bitness        ;;   entry point to make the initial
    call    switchEntryPoint    ;;   switch into protected mode
    jc    @@fail

    call    _fixup            ;; re fixup this exe
    call    _installHandlers    ;; install default exception handlers
    xor    ax, ax
    jmp    short @@exit
@@fail:
    mov    ax, 1
@@exit:
    ret
DPMIEnterProtectedMode ENDP

;;======================================================================
;; Function: Allocate Descriptors
;;
;; Synopsis:
;;
;;    int DPMIAllocateDescriptors(
;;        uShort howMany,        ;; how many descriptors to allocate
;;        selector_t *baseSel);    ;; receives selector of first desc
;;
;; Description:
;;
;;    This function allocates one or more LDT descriptors. The howMany
;;    argument is the number of descriptors to allocate, and the
;;    selector of the first allocated descriptor is written to the
;;    address pointed to by the baseSel argument.  When more than one
;;    descriptor  is allocated, they are consecutive, i.e., the
;;    difference between them is obtained by calling DPMIGetSelectorDelta.
;;
;;    At the time of allocation, each descriptor is of type DATA with
;;    a base and limit of zero.  It is the client's responsibility to
;;    set up the descriptors with meaningful values.
;;
;; DPMI reference: INT 31h AX=0000h
;;
;; Version 1.0 Error returns:
;;
;;    8011h    descriptor unavailable.

DPMIAllocateDescriptors PROC C    \
    howMany:uShort,        \
    baseSel:PTR

    mov    ax, 0000h
    mov    cx, howMany
    int    31h
    jc    @@fail

    ldptr    bx, baseSel
    mov    [bx], ax
    xor    ax, ax
    jmp    short @@exit
@@fail:
    mov    ax, 1
@@exit:
    ret
DPMIAllocateDescriptors ENDP

;;======================================================================
;; Function: Free Descriptor
;;
;; Synopsis:
;;
;;    int DPMIFreeDescriptor(
;;        selector_t sel);    ;; Selector of descriptor to free
;;
;; Description:
;;
;;    This function returns the specified descriptor to the DPMI host.
;;
;; DPMI reference: INT 31h AX=0001h
;;
;; Version 1.0 Error returns:
;;
;;    8022h    invalid selector

DPMIFreeDescriptor PROC C    \
    sel:selector_t

    mov    ax, 0001h
    mov    bx, sel
    int    31h
    jc    @@exit

    xor    ax, ax
@@exit:
    ret
DPMIFreeDescriptor ENDP

;;======================================================================
;; Function: Create Descriptor to Address Real Segment
;;
;; Synopsis:
;;
;;    int DPMIParaToSelector(
;;        uShort para,        ;; paragraph to map
;;        selector_t *sel);    ;; selector to address paragraph
;;
;; Description:
;;
;;    This function creates a data descriptor whose base corresponds
;;    to the real mode paragraph specified by the para argument.  The
;;    function writes the selector of the created descriptor at the
;;    address pointed to by the sel argument.  The descriptor limit
;;    is 64 KB.
;;
;;    The function is intended to be used only for commonly accessed
;;    regions of the low megabyte, for example, paragraphs 40h, A000h,
;;    and B800h. Descriptors allocated by this function should not be
;;    modified or freed.  Multiple calls to this function with the same
;;    input return the same selector.
;;
;; DPMI reference: INT 31h AX=0002h
;;
;; Version 1.0 Error returns:
;;
;;    8011h    descriptor unavailable

DPMIParaToSelector PROC C    \
    para:uShort,        \
    sel:PTR

    mov    ax, 0002h
    mov    bx, para
    int    31h
    jc    @@exit

    ldptr    bx, sel
    mov    [bx], ax
    xor    ax, ax
@@exit:
    ret
DPMIParaToSelector ENDP

;;======================================================================
;; Function: Get Selector Delta
;;
;; Synopsis:
;;
;;    uShort DPMIGetSelectorDelta(void);
;;
;; Description:
;;
;;    The return value of this function is the difference between
;;    consecutive selectors.
;;
;; DPMI reference: INT 31h AX=0003h

DPMIGetSelectorDelta PROC C
    mov    ax, 0003h
    int    31h
    ret
DPMIGetSelectorDelta ENDP

;;======================================================================
;; Function: Get Segment Base
;;
;; Synopsis:
;;
;;    int DPMIGetSegmentBase(
;;        selector_t sel,        ;; selector of segment to get base of
;;        uLong *base);        ;; location to receive base of segment
;;
;; Description:
;;
;;    This function retrieves the base of the segment specified by the
;;    sel argument.  The linear base of the segment is written at the
;;    address pointed to by the base argument.
;;
;; DPMI reference: INT 31h AX=0006h
;;
;; Version 1.0 Error returns:
;;
;;    8022h    invalid selector

DPMIGetSegmentBase PROC C    \
    sel:selector_t,        \
    base:PTR

    mov    ax, 0006h
    mov    bx, sel
    int    31h
    jc    @@exit

    ldptr    bx, base
    stlong    [bx], cx, dx

    xor    ax, ax
@@exit:
    ret
DPMIGetSegmentBase ENDP

;;======================================================================
;; Function: Set Segment Base
;;
;; Synopsis:
;;
;;    int DPMISetSegmentBase(
;;        selector_t sel,        ;; selector of segment to set base of
;;        uLong base);        ;; new value for base
;;
;; Description:
;;
;;    This function sets the base of the segment specified by the sel
;;    argument to the value of the base argument.
;;
;; DPMI reference: INT 31h AX=0007h
;;
;; Version 1.0 Error returns:
;;
;;    8022h    invalid selector
;;    8025h    invalid linear address

DPMISetSegmentBase PROC C    \
    sel:selector_t,        \
    base:uLong

    mov    ax, 0007h
    mov    bx, sel
    ldlong    cx, dx, base
    int    31h
    jc    @@exit

    xor    ax, ax
@@exit:
    ret
DPMISetSegmentBase ENDP

;;======================================================================
;; Function: Get Segment Limit
;;
;; Synopsis:
;;
;;    int DPMIGetSegmentLimit(
;;        selector_t sel,        ;; selector of segment to get limit of
;;        uLong *limit);        ;; location to receive limit
;;
;; Description:
;;
;;    This function retrieves retrieves the limit of the segment
;;    specified by the sel argument, and writes it at the address
;;    pointed to by the limit argument.  The function is implemented
;;    not by a DPMI call, but with the LSL instruction.
;;
;;
;; DPMI reference: Not a true DPMI function, but included for completeness.
;;

DPMIGetSegmentLimit PROC C    \
    sel:selector_t,        \
    limit:PTR

    mov    ax, 0400h    ;; check processor type
    int    31h
    cmp    cl, 2        ;; 2 means 286
    je    @@is286
.386p
    movzx    eax, sel
    lsl    eax, eax
    jnz    @@fail
    ldptr    bx, limit
    mov    [bx], eax
    xor    ax, ax
    jmp    short @@exit
.286p
@@is286:
    mov    ax, sel
    lsl    ax, ax        ;; get segment limit
    jnz    @@fail        ;; zf=0 if cannot access

    ldptr    bx, limit
    stlong    [bx], 0, ax
    xor    ax, ax
    jmp    short @@exit
@@fail:
    mov    ax, 1
@@exit:
    ret
DPMIGetSegmentLimit ENDP

;;======================================================================
;; Function: Set Segment Limit
;;
;; Synopsis:
;;
;;    int DPMISetSegmentLimit(
;;        selector_t sel,        ;; selector of segment to set limit of
;;        uLong limit);        ;; desired segment limit
;;
;;
;; Description:
;;
;;    This function sets the limit of the segment specified by the
;;    sel argument to the value given by the limit argument.
;;
;; DPMI reference: INT 31h AX=0008h
;;
;; Version 1.0 Error returns:
;;
;;    8021h    invalid value
;;    8022h    invalid selecotr
;;    8023h    invalid linear address

DPMISetSegmentLimit PROC C    \
    sel:selector_t,        \
    limit:uLong

    mov    ax, 0008h
    mov    bx, sel
    ldlong    cx, dx, limit
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMISetSegmentLimit ENDP

;;======================================================================
;; Function: Get Segment Attributes
;;
;; Synopsis:
;;
;;    int DPMIGetSegmentAttributes(
;;        selector_t sel,        ;; selector of segment to get attribs
;;        uChar *arb,        ;; receives access rights/type byte
;;        uChar *arb386);        ;; receives extended access byte(386+)
;;
;;
;; Description:
;;
;;    This function gets the attributes of the segment specified by the
;;    sel argument. The location pointed to by the arb argument receives
;;    the 6th byte of the descriptor, and the location pointed to by
;;    the arb386 argument returns the 8th byte of the descriptor.  This
;;    function is implemented with the LAR instruction.
;;
;; DPMI reference: Not a true DPMI function, but included for completeness.
;;

DPMIGetSegmentAttributes PROC C    \
    sel:selector_t,        \
    arb:PTR,        \
    arb386:PTR

    mov    ax, 0400h        ;; check processor type
    int    31h
    cmp    cl, 2            ;; 2 means 286
    je    @@is286
.386p
    movzx    eax, sel
    lar    eax, eax
    jnz    @@fail            ;; zf=0 means cannot access descriptor

    shr    eax, 8
    ldptr    bx, arb386
    mov    [bx], ah
    jmp    short getArb
.286p
@@is286:
    ldptr    bx, arb386
    mov    byte ptr [bx], 0

getArb:
    lar    ax, sel
    jnz    @@fail
    ldptr    bx, arb
    mov    [bx], ah

    xor    ax, ax
    jmp    short @@exit
@@fail:
    mov    ax, 1
@@exit:
    ret
DPMIGetSegmentAttributes ENDP

;;======================================================================
;; Function: Set Segment Attributes
;;
;; Synopsis:
;;
;;    int DPMISetSegmentAttributes(
;;        selector_t sel,        ;; selector of segment to set attribs
;;        uChar arb,        ;; access rights/type byte
;;        uChar arb386);        ;; extended access byte (386+)
;;
;;
;; Description:
;;
;;    This function sets the attributes of the segment specified by
;;    the sel argument.  The arb argument is the 6th byte of the
;;    descriptor, and the arb386 argument is the 8th byte of the
;;    descriptor.  Attempts to set privilege levels more privileged
;;    than the client level will fail.
;;
;; DPMI reference: INT 31h AX=0009h
;;
;; Version 1.0 Error returns:
;;
;;    8021h    invalid value
;;    8022h    invalid selector
;;    8025h    invalid linear address

DPMISetSegmentAttributes PROC C    \
    sel:selector_t,        \
    arb:uChar,        \
    arb386:uChar

    mov    ax, 0009h
    mov    bx, sel
    mov    cl, arb
    mov    ch, arb386
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMISetSegmentAttributes ENDP

;;======================================================================
;; Function: Create Alias Descriptor
;;
;; Synopsis:
;;
;;    int DPMICreateAlias(
;;        selector_t sel,        ;; selector to create alias for
;;        selector_t *alias);    ;; receives selector of alias segment
;;
;;
;; Description:
;;
;;    This function creates a descriptor with the same base and limit
;;    as the descriptor specified by the sel argument.  It writes the
;;    selector of the alias descriptor at the address pointed to by
;;    the alias argument.  The descriptor that this function creates is
;;    of type data.  The DPMI host does not maintain an association
;;    between the aliased descriptors.
;;
;; DPMI reference: INT 31h AX=000Ah
;;
;; Version 1.0 Error returns:
;;
;;    8011h    descriptor unavailable
;;    8022h    invalid selector

DPMICreateAlias PROC C    \
    sel:selector_t,    \
    aliasSel:PTR

    mov    ax, 000Ah
    mov    bx, sel
    int    31h
    jc    @@exit

    ldptr    bx, aliasSel
    mov    [bx], ax
    xor    ax, ax
@@exit:
    ret
DPMICreateAlias ENDP

;;======================================================================
;; Function: Get Raw LDT Descriptor
;;
;; Synopsis:
;;
;;    int DPMIGetDescriptor(
;;        selector_t sel,                ;; descriptor to get
;;        struct descriptor_t *descriptor);    ;; struct to receive
;;
;;
;; Description:
;;    This function copies the contents of the LDT descriptor specified
;;    by the sel argument to the structure pointed to by the descriptor
;;    argument.
;;
;; DPMI reference: INT 31h AX=000Bh
;;
;; Version 1.0 Error returns:
;;
;;    8022h    invalid selector

DPMIGetDescriptor PROC C USES DI,    \
    sel:selector_t,            \
    descriptor:PTR

    mov    ax, 000Bh
    mov    bx, sel
    ldptr    di, descriptor, es
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIGetDescriptor ENDP

;;======================================================================
;; Function: Set Raw LDT Descriptor
;;
;; Synopsis:
;;
;;    int DPMISetDescriptor(
;;        selector_t sel,                ;; descriptor to set
;;        struct descriptor_t *descriptor);    ;; descriptor contents
;;
;;
;; Description:
;;
;;    This function copies the contents of the structure pointed to
;;    by the descriptor argument to the LDT entry specified by the
;;    sel argument.  If the present bit is set, the
;;
;; DPMI reference: INT 31h AX=000Ch
;;
;; Version 1.0 Error returns:
;;
;;    8021h    invalid value
;;    8022h    invalid selector
;;    8025h    invalid linear address

DPMISetDescriptor PROC C USES DI, \
    sel:selector_t,          \
    descriptor:PTR

    mov    ax, 000Ch
    mov    bx, sel
    ldptr    di, descriptor, es
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMISetDescriptor ENDP

;;======================================================================
;; Function: Allocate Specific LDT Descriptor
;;
;; Synopsis:
;;
;;    int DPMIAllocateSpecificDescriptor(
;;        selector_t sel);    ;; selector of descriptor to allocate
;;
;;
;; Description:
;;    This function allocates a specific LDT descriptor in the range
;;    04h to 7Ch. It is intended for use only with DOS extended applications
;;    that require compatibility with pre-DPMI environments.
;;
;; DPMI reference: INT 31h AX=000Dh
;;
;; Version 1.0 Error returns:
;;
;;    8011h    descriptor unavailable
;;    8022h    invalid selector

DPMIAllocateSpecificDescriptor PROC C    \
    sel:selector_t

    mov    ax, 000Dh
    mov    bx, sel
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIAllocateSpecificDescriptor ENDP

;;======================================================================
;; Function: Allocate DOS Memory Block
;;
;; Synopsis:
;;
;;    int DPMIAllocateDOSMemory(
;;        uShort nParas,        ;; number of paragraphs to allocate
;;        uShort *para,        ;; receives para of alloc'ed block
;;        selector_t *sel,    ;; receives selector of alloc'ed block
;;        uShort *maxParas);    ;; receives max avail in fail case
;;
;;
;; Description:
;;
;;    This function allocates a block of memory from DOS.  The block so
;;    allocated is guaranteed to reside below 1 MB, and thus be addressable
;;    by real mode code.  The desired size of the block is specified by
;;    the nParas argument, which should be set to the number of paragraphs
;;    (16 bytes each) for the block.  The DPMI host provides both a
;;    paragraph address (which is written at the address pointed to by the
;;    para argument),and a selector (which is written at the address
;;    pointed to by the sel argument.
;;
;;    If the requested size of the block is greater than 64 KB (4096 paras),
;;    the DPMI host creates a set of descriptors sufficient to span the
;;    allocated region, with consecutive selectors and bases that differ
;;    by 64 KB.
;;
;;    In the case where there is insufficient memory to satisfy the request,
;;    the DPMI host writes the maximum number of paragraphs available to
;;    the address pointed to by the maxParas argument.
;;
;;
;; DPMI reference: INT 31h AX=0100h
;;
;; Error returns (valid for version 0.9)
;;
;;    0007h    memory control blocks damaged
;;    0008h    insufficient memory

DPMIAllocateDOSMemory PROC C    \
    nParas:uShort,        \
    para:PTR,        \
    sel:PTR,        \
    maxParas:PTR

    mov    ax, 0100h
    mov    bx, nParas
    int    31h
    jc    @@fail

    ldptr    bx, para
    mov    [bx], ax
    ldptr    bx, sel
    mov    [bx], dx

    xor    ax,ax
    jmp    short @@exit
@@fail:
    mov    cx, bx
    ldptr    bx, maxParas
    mov    [bx], cx
@@exit:
    ret
DPMIAllocateDOSMemory ENDP

;;======================================================================
;; Function: Free DOS Memory Block
;;
;; Synopsis:
;;
;;    int DPMIFreeDOSMemory(
;;        selector_t sel);    ;; selector of block to free
;;
;;
;; Description:
;;
;;    This function frees a DOS memory block allocated by the function
;;    DPMIAllocateDOSMemory.  The argument is the selector of the
;;    block to be freed. If the DOS block is larger than 64 KB, all of
;;    the descriptors that were allocated for the block are freed.d
;;
;; DPMI reference: INT 31h AX=0101h
;;
;; Error returns (valid for version 0.9):
;;
;;    0007h    memory control blocks damaged
;;    0009h    incorrect memory segment specified

DPMIFreeDOSMemory PROC C    \
    sel:selector_t

    mov    ax, 0101h
    mov    dx, sel
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIFreeDOSMemory ENDP

;;======================================================================
;; Function: Resize DOS Memory Block
;;
;; Synopsis:
;;
;;    int DPMIResizeDOSMemory(
;;        selector_t sel,        ;; selector of block to resize
;;        uShort nParas,        ;; desired size of block in paras
;;        uShort *maxParas);    ;; receives max paras available
;;
;;
;; Description:
;;
;;    This function changes the size of a block that was allocated with
;;    the function DPMIAllocateDOSMemory.  The nParas argument specifies
;;    the desired new size of the block, in paragraphs.  The sel argument
;;    is the selector of the block to be resized.
;;
;;    In the case where there is insufficient memory to satisfy the request,
;;    the DPMI host writes the maximum number of paragraphs available to
;;    the address pointed to by the maxParas argument.
;;
;; DPMI reference: INT 31h AX=102h
;;
;; Error returns (valid for version 0.9):
;;
;;    0007h    memory control blocks damaged
;;    0008h    insufficient memory
;;    0009h    incorrect memory segment

DPMIResizeDOSMemory PROC C    \
    sel:selector_t,        \
    nParas:uShort,        \
    maxParas:PTR

    mov    ax, 0102h
    mov    bx, nParas
    mov    dx, sel
    int    31h
    jc    @@fail

    xor    ax, ax
    jmp    short @@exit
@@fail:
    mov    cx, bx
    ldptr    bx, maxParas
    mov    [bx], cx
@@exit:
    ret
DPMIResizeDOSMemory ENDP

;;======================================================================
;; Function: Get Real Mode Interrupt Vector
;;
;; Synopsis:
;;
;;    void DPMIGetRealInterruptVector(
;;        uChar vector,            ;; vector number to get
;;        void (far* *realIsr)());    ;; receives real vector
;;
;;
;; Description:
;;
;;    This function retrieves the real mode paragraph:offset address of
;;    the real mode interrupt handler specified by the vector argument.
;;    The handler address is written to the address pointed to by the
;;    realIsr argument.
;;
;;
;; DPMI reference: INT 31h AX=0200h
;;

DPMIGetRealInterruptVector PROC C    \
    vector:uChar,            \
    realIsr:PTR

    mov    ax, 0200h
    mov    bl, vector
    int    31h
    ldptr    bx, realIsr
    stlong    [bx], cx, dx

    ret
DPMIGetRealInterruptVector ENDP

;;======================================================================
;; Function: Set Real Mode Interrupt Vector
;;
;; Synopsis:
;;
;;    void DPMISetRealInterruptVector(
;;        uChar vector,            ;; vector number to set
;;        void (far *realIsr)());        ;; new real vector
;;
;;
;; Description:
;;
;;    This function sets the real mode interrupt vector specified by the
;;    vector argument to the value in the realIsr argument.  The handler
;;    address in realIsr must be a real mode paragraph:offset address.
;;
;; DPMI reference: INT 31h AX=0201h
;;

DPMISetRealInterruptVector PROC C    \
    vector:uChar,            \
    realIsr:FAR PTR

    mov    ax, 0201h
    mov    bl, vector
    ldlong    cx, dx, realIsr
    int    31h
    ret
DPMISetRealInterruptVector ENDP

;;======================================================================
;; Function: Get Processor Exception Vector
;;
;; Synopsis:
;;
;;    int DPMIGetExceptionVector(
;;        uChar exception,        ;; exception number to get
;;        void (far* *excHandler)());    ;; receives handler address
;;
;;
;; Description:
;;
;;    This function retrieves the address of the exception handler
;;    specified by the exception argument (range 0-1Fh).  The handler
;;    address is written to the address pointed to by the
;;    excHandler argument.
;;
;; DPMI reference: INT 31h AX=0202h
;;
;; Version 1.0 Error returns:
;;
;;    8021h    invalid value

DPMIGetExceptionVector PROC C    \
    exception:uChar,    \
    excHandler:PTR

    mov    ax, 0202h
    mov    bl, exception
    int    31h
    jc    @@exit

    ldptr    bx, excHandler
    stlong    [bx], cx, dx

    xor    ax, ax
@@exit:
    ret
DPMIGetExceptionVector ENDP

;;======================================================================
;; Function: Set Processor Exception Vector
;;
;; Synopsis:
;;
;;    int DPMISetExceptionVector(
;;        uChar exception,        ;; exception number to set
;;        void (far *excHandler)());    ;; new handler address
;;
;;
;; Description:
;;
;;    This function sets the exception vector specified by the
;;    exception argument to the value in the excHandler argument.
;;
;;    The exception handler is defined as follows:
;;
;;        void _saveregs _far excHandler(struct excFrame);
;;
;;    The exception handler may modify the fields of the excFrame structure.
;;    When the handler returns, the DPMI host uses the new values from
;;    the structure to restart the faulting client.
;;
;; DPMI reference: INT 31h AX=0203h
;;
;; Version 1.0 Error returns:
;;
;;    8021h    invalid value
;;    8022h    invalid selector

DPMISetExceptionVector PROC C    \
    exception:uChar,    \
    excHandler:FAR PTR

    mov    ax, 0203h
    mov    bl, exception
    ldlong    cx, dx, excHandler
    int    31h
    jc    @@exit

    xor    ax, ax
@@exit:
    ret
DPMISetExceptionVector ENDP

;;======================================================================
;; Function: Get Protected Mode Interrupt Vector
;;
;; Synopsis:
;;
;;    void DPMIGetProtInterruptVector(
;;        uChar vector,            ;; interrupt vector to get
;;        void (far* *protIsr)());    ;; receives interrupt vector
;;
;; Description:
;;
;;    This function retrieves the protected mode interrupt vector
;;    specified by the vector argument.  The selector:offset address of
;;    the current interrupt handler is written to the address pointed to
;;    by the protIsr argument.
;;
;; DPMI reference: INT 31h AX=0204h
;;

DPMIGetProtInterruptVector PROC C    \
    vector:uChar,            \
    protIsr:PTR

    mov    ax, 0204h
    mov    bl, vector
    int    31h
    ldptr    bx, protIsr
    stlong    [bx], cx, dx

    ret
DPMIGetProtInterruptVector ENDP

;;======================================================================
;; Function: Set Protected Mode Interrupt Vector
;;
;; Synopsis:
;;
;;    int DPMISetProtInterruptVector(
;;        uChar vector,            ;; interrupt vector to set
;;        void (far *protIsr)());        ;; new handler address
;;
;;
;; Description:
;;
;;    This function sets the address of the protected mode interrupt
;;    handler for the vector specified by the vector arugment.  The
;;    protIsr argument is the selector:offset of the desired new
;;    handler.
;;
;; DPMI reference: INT 31h AX=0205h
;;
;; Version 1.0 Error returns:
;;
;;    8022h    invalid selector

DPMISetProtInterruptVector PROC C    \
    vector:uChar,            \
    protIsr:FAR PTR

    mov    ax, 0205h
    mov    bl, vector
    ldlong    cx, dx, protIsr
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMISetProtInterruptVector ENDP

;;======================================================================
;; Function: Issue Real Mode Interrupt
;;
;; Synopsis:
;;
;;    int DPMIIssueRealInterrupt(
;;        uChar vector,            ;; interrupt to issue
;;        uShort nArgBytes,        ;; number of bytes of args
;;        struct dpmiRegs_t *regs,    ;; real mode register state
;;        ...);
;;
;;
;; Description:
;;
;;    This function switches to real mode and issues the interrupt
;;    specified by the vector argument.  Prior to issuing the interrupt,
;;    the DPMI host loads the processor registers with the contents of
;;    the structure pointed to by the regs argument.  When the interrupt
;;    handler returns, the DPMI host updates the register structure to
;;    reflect changes caused by the interrupt handler.
;;
;;    The CS:IP field of the real call structure is ignored, because the
;;    execution address is determined by the real mode interrupt vector.
;;
;; DPMI reference: INT 31h AX=0300h
;;
;; Version 1.0 Error returns:
;;
;;    8012h    linear memory unavailable
;;    8013h    physical memory unavailable
;;    8014h    backing store unavailable
;;    8021h    invalid value

DPMIIssueRealInterrupt PROC C USES DS SI DI,    \
    vector:BYTE,                \
    nArgBytes:uShort,            \
    regs:PTR,                \
    arguments:BYTE

    mov    cx, nArgBytes        ;; copy stack arguments
    jcxz    @@doCall
    sub    sp, cx
    mov    di, sp
    lea    si, arguments
    mov    ax, ss
    mov    ds, ax
    mov    es, ax
    cld
    rep movsb
@@doCall:
    mov    ax, 0300h
    xor    bh, bh
    mov    bl, vector
    mov    cx, nArgBytes
    ldptr    di, regs, es
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    add    sp, nArgBytes
    ret
DPMIIssueRealInterrupt ENDP

;;======================================================================
;; Function: Call Real Mode Procedure with Far Return
;;
;; Synopsis:
;;
;;    int DPMICallRealProcedure(
;;        uShort nArgBytes,        ;; number of bytes of args
;;        struct dpmiRegs_t *regs,    ;; real mode register state
;;        ...);                ;; function arguments
;;
;; Description:
;;
;;    This function causes the DPMI host to switch to real mode, push
;;    zero or more argument bytes on the stack, and call the far function
;;    indicated by the CS:IP fields of the real call structure pointed
;;    to by the regs argument.  The number of argument bytes to push is
;;    given by the nArgBytes argument, and the function arguments should
;;    follow the pointer to the real call structure in the arugment list.
;;    The real function must return on the same stack on which it was
;;    called.
;;
;;    The DPMI host reloads the register structure with the register
;;    current register state when the far function returns.
;;
;; DPMI reference: INT 31h AX=0301h
;;
;; Version 1.0 Error returns:
;;
;;    8012h    linear memory unavailable
;;    8013h    physical memory unavailable
;;    8014h    backing store unavailable
;;    8021h    invalid value

DPMICallRealProcedure PROC C USES DS SI DI,    \
    nArgBytes:uShort,            \
    regs:PTR,                \
    arguments:BYTE

    mov    cx, nArgBytes        ;; copy stack arguments
    jcxz    @@doCall
    sub    sp, cx
    mov    di, sp
    lea    si, arguments
    mov    ax, ss
    mov    ds, ax
    mov    es, ax
    cld
    rep movsb
@@doCall:
    mov    ax, 0301h
    xor    bh, bh
    mov    cx, nArgBytes
    ldptr    di, regs, es
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    add    sp, nArgBytes
    ret
DPMICallRealProcedure ENDP

;;======================================================================
;; Function: Call Real Mode Procedure with IRET
;;
;; Synopsis:
;;
;;    int DPMICallRealInterruptProcedure(
;;        uShort nArgBytes,        ;; number of bytes of args
;;        struct dpmiRegs_t *regs,    ;; real mode register state
;;        ...);                ;; function arguments.
;;
;;
;; Description:
;;
;;    This function is identical to DPMICallRealProcedure, except that
;;    it is used to call a real function that returns with an IRET
;;    instead of a RETF.
;;
;; DPMI reference: INT 31h AX=0302h
;;
;; Version 1.0 Error returns:
;;
;;    8012h    linear memory unavailable
;;    8013h    physical memory unavailable
;;    8014h    backing store unavailable
;;    8021h    invalid value

DPMICallRealInterruptProcedure PROC C USES DS SI DI, \
    nArgBytes:uShort,            \
    regs:PTR,                \
    arguments:BYTE

    mov    cx, nArgBytes        ;; copy stack arguments
    jcxz    @@doCall
    sub    sp, cx
    mov    di, sp
    lea    si, arguments
    mov    ax, ss
    mov    ds, ax
    mov    es, ax
    cld
    rep movsb
@@doCall:
    mov    ax, 0302h
    xor    bh, bh
    mov    cx, nArgBytes
    ldptr    di, regs, es
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    add    sp, nArgBytes
    ret
DPMICallRealInterruptProcedure ENDP

;;======================================================================
;; Function: Allocate Real Mode Callback
;;
;; Synopsis:
;;
;;    int DPMIAllocateRealCallBack(
;;        struct dpmiRegs_t *regs,    ;; address of static reg state
;;        void (far *handler)(),        ;; prot mode callback handler
;;        void (far* *cbAddr)());        ;; receives real callback addr
;;
;; Description:
;;
;;    This function allocates a real mode callback from the DPMI host.
;;    A real mode callback is a real mode address (paragraph:offset) that
;;    a real mode caller uses to invoke a protected mode callback
;;    handler.  This provides a mechanism for calling protected mode
;;    from real mode.
;;
;;    The cbAddr argument points to the location to receive the real mode
;;    callback address.  When called, the DPMI host passes control to
;;    the protected mode address specified by the handler argument.
;;
;;    The protected mode handler  is passed (in ES:DI) a pointer to the
;;    real mode call structure whose address is passed  to this function
;;    in the regs argument.  Therefore, this structure should be statically
;;    allocated.  The DPMI host is responsible for loading the structure
;;    with the register state at the time of the callback prior to passing
;;    it to the protected mode callback handler. The handler is also
;;    passed (in DS:SI) the address of the real mode stack.
;;
;;    The DPMI host uses the register state in the call structure
;;    to restart the real mode caller.  It is the responsibility of the
;;    protected mode handler to locate the real mode return address on
;;    the real mode stack, and store it in the CS:IP fields of the call
;;    structure in order to effect a return from the callback.
;;
;; DPMI reference: INT 31h AX=0303h
;;
;; Version 1.0 Error returns:
;;
;;    8015h    callback unavailable

DPMIAllocateRealCallBack PROC C    USES DS SI DI,     \
    regs:PTR,                \
    handler:FAR PTR,            \
    cbAddr:PTR

    push    ds
    mov    ax, 0303h
    ldptr    di, regs, es
    ldlong    ds, si, handler
    int    31h
    jc    @@fail

    pop    ds
    ldptr    bx, cbAddr
    stlong    [bx], cx, dx
    xor    ax, ax
    jmp    short @@exit
@@fail:
    pop    ds
@@exit:
    ret
DPMIAllocateRealCallBack ENDP

;;======================================================================
;; Function: Free Real Mode Callback
;;
;; Synopsis:
;;
;;    int DPMIFreeRealCallBack(
;;        void (far *cbAddr)());        ;; callback to free
;;
;;
;; Description:
;;
;;    This function frees a real mode callback allocated by
;;    DPMIAllocateRealCallBack.  The cbAddr is the callback
;;    address to be freed.
;;
;; DPMI reference: INT 31h AX=0303h
;;
;; Version 1.0 Error returns:
;;
;;    8024h    invalid callback address

DPMIFreeRealCallBack PROC C    \
    cbAddr:FAR PTR

    mov    ax, 0304h
    ldlong    cx, dx, cbAddr
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIFreeRealCallBack ENDP

;;======================================================================
;; Function: Get State Save/Restore Procedure Addresses
;;
;; Synopsis:
;;
;;    void DPMIGetStateSaveRestoreProcs(
;;        uShort *stateSize,        ;; size of state info
;;        void (far* *realProc)(),    ;; receives real save/rst proc
;;        void (far* *protProc)());    ;; receives prot save/rst proc
;;
;; Description:
;;
;;    This function retrieves information from the DPMI host that
;;    is required for saving and restoring the client state when
;;    using the raw mode switch function.
;;
;;    The DPMI specification requires that clients save their state
;;    prior to making a raw mode switch, and subsequently restore it.
;;    This function provides the size of the state information, and
;;    the both the protected mode and real mode addresses of functions
;;    to call to save and restore the client state.
;;
;;    The size of the state information, in bytes, is stored at the
;;    address pointed to by the stateSize argument.  The address of the
;;    far procedure to call from real mode to save or restore the client
;;    state is stored at the address pointed to by the realProc argument.
;;    The address of the far procedure to call from protected mode to
;;    save and restore the client state is stored at the address pointed
;;    to by the protProc argument.
;;
;;    The state save/restore procedures are called with AL=0 to save the
;;    state, and AL=1 to restore the state.  In both cases, ES:DI points
;;    to the state information buffer.
;;
;;
;; DPMI reference: INT 31h AX=0305h

DPMIGetStateSaveRestoreProcs PROC C USES SI DI,    \
    stateSize:PTR,        \
    realProc:PTR,        \
    protProc:PTR

    mov    ax, 0305h
    int    31h

    mov    dx, bx

    ldptr    bx, stateSize
    mov    [bx], ax
    ldptr    bx, realProc
    stlong    [bx], dx, cx
    ldptr    bx, protProc
    stlong    [bx], si, di

    ret
DPMIGetStateSaveRestoreProcs ENDP

;;======================================================================
;; Function: Save Or Restore Client State for Raw Switch
;;
;; Synopsis:
;;
;;    void DPMISaveOrRestoreState(
;;        int saveRestore,        ;; 0=save 1=restore
;;        uChar *stateBuffer,        ;; pointer to state buffer
;;        void (far *procAddr)());    ;; procedure to call
;;
;; Description:
;;
;;    This function invokes the save/restore procedure whose address
;;    is specified by the procAddr argument.  The stateBuffer argument
;;    points to the buffer to supply or receive the client state. Its
;;    size is determined by calling DPMIGetStateSaveRestoreProcs. The
;;    saveRestore argument is zero to perform state save, or one to
;;    perform a state restore.

DPMISaveOrRestoreState PROC C USES DI,    \
    saveRestore:WORD,        \
    stateBuffer:PTR,        \
    procAddr:FAR PTR

    mov    ax, saveRestore
    ldptr    di, stateBuffer, es
    call    procAddr

    ret
DPMISaveOrRestoreState ENDP

;;======================================================================
;; Function: Get Raw Switch Procedure Addresses
;;
;; Synopsis:
;;
;;    void DPMIGetRawSwitchProc(
;;        void (far* *realToProt)(),    ;; real to prot switch addr
;;        void (far* *protToReal)());    ;; prot to real switch addr
;;
;; Description:
;;
;;    This function retrieves information from the DPMI host that
;;    is required for raw mode switching.  The address (paragraph:offset)
;;    of the real to protected mode service is stored at the address
;;    pointed to by the realToProt argument.  The address (selector:offset)
;;    of the protected to real mode service is stored at the address
;;    pointed to by the protToReal argument.
;;
;; DPMI reference: INT 31h AX=0306h

DPMIGetRawSwitchProc PROC C USES SI DI,    \
    realToProt:PTR,            \
    protToReal:PTR

    mov    ax,0306h
    int    31h

    mov    dx, bx
    ldptr    bx, realToProt
    stlong    [bx], dx, cx
    ldptr    bx, protToReal
    stlong    [bx], si, di

    ret
DPMIGetRawSwitchProc ENDP

;;======================================================================
;; Function: Do Raw Mode Switch
;;
;; Synopsis:
;;
;;    void DPMIDoRawSwitch(
;;        void (far *switchAddr)(),    ;; switch service address
;;        struct rawModeRegs_t *rawRegs);    ;; new register values
;;
;; Description:
;;
;;    This function invokes the raw switch service.  The switchAddr
;;    argument is obtained from DPMIGetRawSwitchProc, and specifies
;;    the address of the switch service to invoke.  When the function
;;    returns, the processor will be in the alternate mode.
;;
;;    The rawRegs argument points to the structure containing the register
;;    contents to be put in effect after the mode switch is effected.
;;    The values in the structure MUST be aliases for the currently active
;;    segment registers.  In other words, when switching from protected
;;    to real mode, each segment register value in the structure must
;;    be the paragraph equivalent of the current protected mode descriptor
;;    value.  Likewise, when switching from real to protected mode, each
;;    segment register value in the structure must be the selector that
;;    maps the current paragraph in each segment register. These
;;    requirements imply that this routine must execute only in the low
;;    1 MB of the address space, and that the stack must also be in the
;;    low 1 MB.
;;
;; DPMI reference: invoking the raw mode switch services

DPMIDoRawSwitch PROC C USES SI DI,     \
    switchAddr:FAR PTR,    \
    rawRegs:PTR

    ldptr    di, rawRegs
    mov    ax, [di].rawDS
    mov    cx, [di].rawES
    mov    dx, [di].rawSS
    mov    bx, sp
    mov    si, [di].rawCS
    mov    di, offset @@cont
    push    word ptr switchAddr+2    ;; push switch address and retf to it
    push    word ptr switchAddr
    retf
@@cont:
    ret
DPMIDoRawSwitch ENDP

;;======================================================================
;; Function: Get DPMI Host Version Information
;;
;; Synopsis:
;;
;;    void DPMIGetVersion(
;;        uChar *major,        ;; receives major version number
;;        uChar *minor,        ;; receives minor version number
;;        uChar *processor,    ;; receives processor code
;;        uShort *flags,        ;; receives flags
;;        uChar *masterPIC,    ;; receives virtual master PIC base
;;        uChar *slavePIC);    ;; receives virtual slave PIC base
;;
;; Description:
;;
;;    This function retrieves version information from the DPMI host.
;;    For version 0.9, the major version is zero and the minor version
;;    is 90 (5Ah).  The processor codes are as follows:
;;
;;        2 => 80286, 3 => 80386, 4 => 80486 5-FFh => future
;;
;;    The bits of the flags word have the following meanings:
;;
;;        Bit    Meaning
;;         0    0 = 16-bit host,
;;            1 = 32-bit host
;;         1    0 = DOS runs in virtual 86 mode,
;;            1 = DOS runs in real
;;         2    0 = no virtual memory support
;;            1 = virtual memory supported
;;
;; DPMI reference: INT 31h AX=0400h

DPMIGetVersion PROC C USES SI,    \
    major:PTR,    \
    minor:PTR,    \
    processor:PTR,    \
    flags:PTR,    \
    masterPIC:PTR,    \
    slavePIC:PTR

    mov    ax, 0400h
    int    31h

    ldptr    si, major
    mov    [si], ah
    ldptr    si, minor
    mov    [si], al
    ldptr    si, flags
    mov    [si], bx
    ldptr    si, processor
    mov    [si], cl
    ldptr    si, masterPIC
    mov    [si], dh
    ldptr    si, slavePIC
    mov    [si], dl

    ret
DPMIGetVersion ENDP

;;======================================================================
;; Function: Get Free Memory Information
;;
;; Synopsis:
;;
;;    void DPMIGetFreeMemory(
;;        struct freeMem_t *freeMem); ;; receives free mem info
;;
;;
;; Description:
;;
;;    This function retrieves free memory information from the DPMI
;;    host.  The freeMem argument is a pointer to the structure to
;;    receive the free memory information. Only the first field
;;    (largestFree) of the free memory structure is guaranteed to be
;;    supported.  The other values are set to 0xffffffff if the
;;    item is unavailable.
;;
;; DPMI reference: INT 31h AX=0500h

DPMIGetFreeMemory PROC C USES DI,    \
    freeMem:PTR

    mov    ax, 0500h
    ldptr    di, freeMem, es
    int    31h
    ret
DPMIGetFreeMemory ENDP

;;======================================================================
;; Function: Allocate Memory Block
;;
;; Synopsis:
;;
;;    int DPMIAllocateMemory(
;;        uLong nBytes,        ;; size of block to allocate
;;        uLong *base,        ;; receives linear base of block
;;        uLong *handle);        ;; receives block handle
;;
;; Description:
;;
;;    This function allocates a memory block.  The nBytes argument
;;    specifies the desired size of the block to allocate, in bytes.
;;    The linear base address of the block that is allocated is
;;    written to the address pointed to by the base argument.  The
;;    block handle is written to the address pointed to by the handle
;;    argument.  The handle is used to free or resize the block.
;;
;; DPMI reference: INT 31h AX=0501h
;;
;; Version 1.0 Error returns:
;;
;;    8012h    linear memory unavailable
;;    8013h    physicl memory unavailable
;;    8014h    backing store unavailable
;;    8016h    handle unavailable
;;    8021h    invalid value

DPMIAllocateMemory PROC C USES SI DI,    \
    nBytes:uLong,            \
    base:PTR,            \
    handle:PTR

    mov    ax, 0501h
    ldlong    bx, cx, nBytes
    int    31h
    jc    @@exit

    mov    ax, bx
    ldptr    bx, base
    stlong    [bx], ax, cx
    ldptr    bx, handle
    stlong    [bx], si, di
    xor    ax, ax
@@exit:
    ret
DPMIAllocateMemory ENDP

;;======================================================================
;; Function: Free Memory Block
;;
;; Synopsis:
;;
;;    int DPMIFreeMemory(
;;        uLong handle);        ;; handle of block to free
;;
;;
;; Description:
;;
;;    This function frees a memory block allocated by DPMIAllocateMemory.
;;
;; DPMI reference: INT 31h AX=0502h
;;
;; Version 1.0 Error returns:
;;
;;    8023h    invalid handle

DPMIFreeMemory PROC C USES SI DI,    \
    handle:uLong

    mov    ax, 0502h
    ldlong    si, di, handle
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIFreeMemory ENDP

;;======================================================================
;; Function: Resize Memory Block
;;
;; Synopsis:
;;
;;    int DPMIResizeMemory(
;;        uLong *handle,        ;;address of handle of block to resize
;;        uLong nBytes,        ;; new desired size in bytes
;;        uLong *base);        ;; receives new linear base of block
;;
;; Description:
;;
;;    This function resizes a memory block allocated by DPMIAllocateMemory.
;;    The handle argument points to the handle of the block to resize.
;;    The nBytes argument is the desired new size of the block, in bytes.
;;    The base argument points to the address to receive the new address
;;    of the block.  Note that both the block handle and the linear base
;;    of the block may be changed by this call.
;;
;; DPMI reference: INT 31h AX=0503h
;;
;; Version 1.0 Error returns:
;;
;;    8012h    linear memory unavailable
;;    8013h    physical memory unavailable
;;    8014h    backing store unavailable
;;    8016h    handle unavailable
;;    8021h    invalid value

DPMIResizeMemory PROC C USES SI DI,    \
    handle:PTR,            \
    nBytes:uLong,            \
    base:PTR

    mov    ax, 0503h
    ldptr    bx, handle
    ldlong    si, di, [bx]
    ldlong    bx, cx, nBytes
    int    31h
    jc    @@exit

    mov    ax, bx
    ldptr    bx, base
    stlong    [bx], ax, cx
    ldptr    bx, handle
    stlong    [bx], si, di
    xor    ax, ax
@@exit:
    ret
DPMIResizeMemory ENDP

;;======================================================================
;; Function: Lock Linear Region of Memory
;;
;; Synopsis:
;;
;;    int DPMILockRegion(
;;        uLong base,        ;; linear address of region to lock
;;        uLong nBytes);        ;; size of region to lock
;;
;; Description:
;;
;;    This function is used to prevent pages from being swapped to disk
;;    by a DPMI host that supports virtual memory.  The base argument is
;;    the linear address of the start of the region to be locked, and the
;;    nBytes argument is the size of the region to lock.  The host maintains
;;    a lock count for each page.  If the DPMI host does not support
;;    virtual memory, the function has no effect.
;;
;; DPMI reference: INT 31h AX=0600h
;;
;; Version 1.0 Error returns:
;;
;;    8013h    physical memory unavailable
;;    8017h    lock count exceeded
;;    8025h    invalid linear address

DPMILockRegion PROC C USES SI DI,    \
    base:uLong,            \
    nBytes:uLong

    mov    ax, 0600h
    ldlong    bx, cx, base
    ldlong    si, di, nBytes
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMILockRegion ENDP

;;======================================================================
;; Function: Unlock Linear Region of Memory
;;
;; Synopsis:
;;
;;    int DPMIUnlockRegion(
;;        uLong base,        ;; linear address of region to unlock
;;        uLong nBytes);        ;; size of region to unlock
;;
;; Description:
;;
;;    This function decrements the lock count for pages in the specified
;;    region.  The base argument is the linear address of the start of the
;;    region, and the nBytes argument is the size of the region in bytes.
;;    Pages are not unlocked until the lock count is zero.
;;
;; DPMI reference: INT 31h AX=0601h
;;
;; Version 1.0 Error returns:
;;
;;    8002h    invalid state
;;    8025h    invalid linear address

DPMIUnlockRegion PROC C USES SI DI,    \
    base:uLong,            \
    nBytes:uLong

    mov    ax, 0601h
    ldlong    bx, cx, base
    ldlong    si, di, nBytes
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIUnlockRegion ENDP

;;======================================================================
;; Function: Mark Real Mode Region as Pageable
;;
;; Synopsis:
;;
;;    int DPMIMarkRealRegionPageable(
;;        uLong base,        ;; linear address of region to mark
;;        uLong nBytes);        ;; size in bytes of region to mark
;;
;; Description:
;;
;;    This function allows memory in the low megabyte of the linear
;;    address space to be swapped to disk by a DPMI host that supports
;;    virtual memory.  The base argument is the linear address of the
;;    start of the region to be made pageable, and the nBytes argument
;;    is the size of the region in bytes.
;;
;; DPMI reference: INT 31h AX=0602h
;;
;; Version 1.0 Error returns:
;;
;;    8002h    invalid state
;;    8025h    invalid linear address

DPMIMarkRealRegionPageable PROC C USES SI DI,    \
    base:uLong,                \
    nBytes:uLong

    mov    ax, 0602h
    ldlong    bx, cx, base
    ldlong    si, di, nBytes
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIMarkRealRegionPageable ENDP

;;======================================================================
;; Function: Relock Real Mode Region
;;
;; Synopsis:
;;
;;    int DPMIRelockRealRegion(
;;        uLong base,        ;; linear address of region to relock
;;        uLong nBytes);        ;; size in bytes of region to relock
;;
;; Description:
;;
;;    This function relocks a memory region in the low 1 MB that was marked
;;    as pageable by DPMIMarkRealRegionPageable.  The base argument is the
;;    linear address of the start of the region to be relocked, and the
;;    nBytes argument is the size of the region in bytes.
;;
;; DPMI reference: INT 31h AX=0603h
;;
;; Version 1.0 Error returns:
;;
;;    8002h    invalid state
;;    8013h    physical meomory unavailable
;;    8025h    invalid linear address

DPMIRelockRealRegion PROC C USES SI DI,    \
    base:uLong,            \
    nBytes:uLong

    mov    ax, 0603h
    ldlong    bx, cx, base
    ldlong    si, di, nBytes
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIRelockRealRegion ENDP

;;======================================================================
;; Function: Get Size of Processor Page
;;
;; Synopsis:
;;
;;    int DPMIGetPageSize(
;;        uLong *pageSize);
;;
;; Description:
;;
;;    This function is used to determine the processor's page size.
;;    The pageSize argument points to the location to receive the
;;    page size, in bytes.  16-bit hosts will fail this call.
;;
;; DPMI reference: INT 31h AX=0604h
;;
;; Version 1.0 Error returns:
;;
;;    8001h    unsupported function

DPMIGetPageSize PROC C \
    pageSize:PTR

    mov    ax, 0604h
    int    31h
    jc    @@exit

    mov    ax, bx
    ldptr    bx, pageSize
    stlong    [bx], ax, cx
    xor    ax, ax
@@exit:
    ret
DPMIGetPageSize ENDP

;;======================================================================
;; Function: Nominate Pages as Demand Paging Candidates
;;
;; Synopsis:
;;
;;    int DPMINominatePages(
;;        uLong base,        ;; base of region to nominate
;;        uLong nBytes);        ;; size in bytes of region
;;
;; Description:
;;
;;    This function is used to indicate to the DPMI host that a range
;;    of memory should be the most likely to be swapped to disk.  The
;;    base argument is the linear address of the start of the region
;;    to be nominated, and the nBytes argument is the size of the region,
;;    in bytes.  The call is advisory only.
;;
;; DPMI reference: INT 31h AX=0702h
;;
;; Version 1.0 Error returns:
;;
;;    8025h    invalid linear address range

DPMINominatePages PROC C USES SI DI,    \
    base:uLong,            \
    nBytes:uLong

    mov    ax, 0702h
    ldlong    bx, cx, base
    ldlong    si, di, nBytes
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMINominatePages ENDP

;;======================================================================
;; Function: Discard Contents of Pages
;;
;; Synopsis:
;;
;;    int DPMIDiscardPageContents(
;;        uLong base,        ;; base of region to discard
;;        uLong nBytes);        ;; size of region in bytes
;;
;; Description:
;;
;;    This function advises the DPMI host to discard the contents of
;;    the specified region to avoid unnecessarily saving them on disk.  The
;;    base argument is the linear address of the start of the region
;;    to be discarded, and the nBytes argument is the size of the region,
;;    in bytes.  The call is advisory only.
;;
;; DPMI reference: INT 31h AX=0703h
;;
;; Version 1.0 Error returns:
;;
;;    8025h    invalid linear address

DPMIDiscardPageContents PROC C USES SI DI,      \
    base:uLong,                \
    nBytes:uLong

    mov    ax, 0703h
    ldlong    bx, cx, base
    ldlong    si, di, nBytes
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIDiscardPageContents ENDP

;;======================================================================
;; Function: Get Linear Address for Physical Region
;;
;; Synopsis:
;;
;;    int DPMIMapPhysicalRegion(
;;        uLong physAddr,        ;; physical address to map
;;        uLong nBytes,        ;; size of region to map
;;        uLong *linear);        ;; receives linear address of region
;;
;; Description:
;;
;;    This function allows a DPMI client to obtain a linear address that
;;    maps to any physical address above 1 MB.  The physAddr argument
;;    specifies the physical address of the region to map. The nBytes
;;    argument is the size of the region to map, in bytes. The linear
;;    argument points to the address to receive the linear address that
;;    the DPMI sets up to map the physical region.
;;
;; DPMI reference: INT 31h AX=0800h
;;
;; Version 1.0 Error returns:
;;
;;    8003h    system integrity
;;    8021h    invalid value

DPMIMapPhysicalRegion PROC C USES SI DI,\
    physAddr:uLong,            \
    nBytes:uLong,            \
    linear:PTR

    mov    ax, 0800h
    ldlong    bx, cx, physAddr
    ldlong    si, di, nBytes
    int    31h
    jc    @@exit

    ldptr    si, linear
    stlong    [si], bx, cx
    xor    ax, ax
@@exit:
    ret
DPMIMapPhysicalRegion ENDP

;;======================================================================
;; Function: Test Virtual Interrupt State and Disable
;;
;; Synopsis:
;;
;;    int DPMITestDisableInts(void);
;;
;; Description:
;;
;;    This function returns the current virtual interrupt enable state,
;;    and disables virtual interrupts.  The return value is zero if
;;    interrupts were previously disabled, and one if they were enabled.
;;
;; DPMI reference: INT 31h AX=0900h

DPMITestDisableInts PROC C
    mov    ax, 0900h
    int    31h
    xor    ah, ah
    ret
DPMITestDisableInts ENDP

;;======================================================================
;; Function: Test Virtual Interrupt State and Enable
;;
;; Synopsis:
;;
;;    int DPMITestEnableInts(void);
;;
;; Description:
;;
;;    This function returns the current virtual interrupt enable state,
;;    and enables virtual interrupts.  The return value is zero if
;;    interrupts were previously disabled, and one if they were enabled.
;;
;; DPMI reference: INT 31h AX=0901h

DPMITestEnableInts PROC C
    mov    ax, 0901h
    int    31h
    xor    ah, ah
    ret
DPMITestEnableInts ENDP

;;======================================================================
;; Function: Test Virtual Interrupt State
;;
;; Synopsis:
;;
;;    int DPMITestInts(void);
;;
;; Description:
;;
;;    This function returns the current virtual interrupt enable state.
;;    The return value is zero if interrupts are disabled, and one if
;;    they are enabled.
;;
;;
;; DPMI reference: INT 31h AX=0902h

DPMITestInts PROC C
    mov    ax, 0902h
    int    31h
    xor    ah, ah
    ret
DPMITestInts ENDP

;;======================================================================
;; Function: Get Vendor Extensions Entry Point
;;
;; Synopsis:
;;
;;    int DPMIGetVendorEntryPoint(
;;        char *extensionID,
;;        void (far* *extAPIEntry)());
;;
;; Description:
;;
;;    This function retrieves an address that can be used to access
;;    vendor specific DPMI extensions.  The extensionID argument points
;;    to a null terminated string that identifies the desired set of
;;    extensions.  The extAPIEntry argument points to the address where
;;    a far pointer to the vendor entry point is to be stored.  The function
;;    returns non-zero if the requested vendor extensions are not found.
;;
;; DPMI reference: INT 31h AX=0A00h and INT 2Fh AX=168Ah
;;
;; Version 1.0 Error returns:
;;
;;    8001h    unsupported function

DPMIGetVendorEntryPoint PROC C USES SI DI,    \
    extensionID:PTR,            \
    extAPIEntry:PTR

    mov    ax, 0A00h
    ldptr    si, extensionID
    int    31h
    jc    @@exit

    ldptr    bx, extAPIEntry
    stlong    [bx], es, di
    xor    ax, ax
@@exit:
    ret
DPMIGetVendorEntryPoint ENDP

;;======================================================================
;; Function: Set Debug Watchpoint
;;
;; Synopsis:
;;
;;    int DPMISetWatchpoint(
;;        uLong linear,        ;; linear address of watchpoint
;;        enum watchSize size,    ;; watchpoint size
;;        enum watchType type,    ;; watchpoint type
;;        uShort *watchHandle);    ;; receives watchpoint handle
;;
;; Description:
;;
;;    This function sets a debug watchpoint using the processor's debug
;;    registers.  The linear argument specifies the linear address of the
;;    watchpoint.  Arguments watchSize and watchType specify the size
;;    and type of the watchpoint.  The watchHandle argument points to the
;;    location to receive the watchpoint handle allocated by the DPMI
;;    host.  Tripping a watchpoint invokes the exception 1 handler.
;;
;; DPMI reference: INT 31h AX=0B00h
;;
;; Version 1.0 Error returns:
;;
;;    8016h    too many breakpoints
;;    8021h    invalid value
;;    8025h    invalid linear address

DPMISetWatchpoint PROC C \
    linear:uLong,    \
    wSize:BYTE,    \
    wType:BYTE,    \
    watchHandle:PTR

    mov    ax, 0B00h
    ldlong    bx, cx, linear
    mov    dl, wSize
    mov    dh, wType
    int    31h
    jc    @@exit
    mov    ax, bx
    ldptr    bx, watchHandle
    mov    [bx], ax
    xor    ax, ax
@@exit:
    ret
DPMISetWatchpoint ENDP

;;======================================================================
;; Function: Clear Debug Watchpoint
;;
;; Synopsis:
;;
;;    int DPMIClearWatchpoint(
;;        uShort watchHandle);    ;; handle of watchpoint to free
;;
;; Description:
;;
;;    This function releases the watchpoint handle allocated by
;;    DPMISetWatchpoint, and clears the associated debug register.
;;    The watchHandle argument is the handle of the watchpoint to free.
;;
;; DPMI reference: INT 31h AX=0B01h
;;
;; Version 1.0 Error returns:
;;
;;    8023h    invalid handle

DPMIClearWatchpoint PROC C    \
    watchHandle:uShort

    mov    ax, 0B01h
    mov    bx, watchHandle
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIClearWatchpoint ENDP

;;======================================================================
;; Function: Get Debug Watchpoint State
;;
;; Synopsis:
;;
;;    int DPMIGetWatchpointState(
;;        uShort watchHandle,    ;;handle of watchpoint to get state of
;;        uChar *tripped);    ;; receives state
;;
;; Description:
;;
;;    This function retrieves the state of a watchpoint set by
;;    DPMISetWatchpoint.  The watchHandle argument is the handle of
;;    watchpoint whose state is to be retrieved.  The tripped argument
;;    receives a zero if the watchpoint has not been encountered,
;;    and receives a one if the watchpoint has been encountered.
;;
;; DPMI reference: INT 31h AX=0B02h
;;
;; Version 1.0 Error returns:
;;
;;    8023h    invalid handle

DPMIGetWatchpointState PROC C    \
    watchHandle:uShort,    \
    tripped:PTR

    mov    ax, 0B02h
    mov    bx, watchHandle
    int    31h
    jc    @@exit
    ldptr    bx, tripped
    mov    [bx], al
    xor    ax, ax
@@exit:
    ret
DPMIGetWatchpointState ENDP

;;======================================================================
;; Function: Reset Debug Watchpoint
;;
;; Synopsis:
;;
;;    int DPMIResetWatchpoint(
;;        uShort watchHandle);    ;; handle of watchpoint to reset
;;
;; Description:
;;
;;    This function resets the state of a watchpoint allocated by
;;    DPMISetWatchpoint.  This sets the watchpoint state to
;;    "not encountered".  The watchHandle argument specifies the watchpoint
;;    in question.
;;
;; DPMI reference: INT 31h AX=0B03h
;;
;; Version 1.0 Error returns:
;;
;;    8023h    invalid handle

DPMIResetWatchpoint PROC C \
    watchHandle:uShort

    mov    ax, 0B03h
    mov    bx, watchHandle
    int    31h
    jc    @@exit
    xor    ax, ax
@@exit:
    ret
DPMIResetWatchpoint ENDP

;;======================================================================
;; Function: Get Current Code Segment
;;
getCS    PROC C
    mov     ax, cs
    ret
getCS    ENDP

;;======================================================================
;; Function: Get Current Data Segment

getDS    PROC C
    mov     ax, ds
    ret
getDS    ENDP




;;======================================================================
;;
;; The remainder of the source module is comprised of routines that
;; re-fix-up the EXE after entering protected mode
;;

relocCountOffset     equ     6
relocTableStart     equ     18h

;;======================================================================
;; Read a word from a file
;;   bx is the handle
;;   ax is the offset
;;
;;   Return word in ax
;;
getWord    PROC C USES DS BX CX DX
    mov    dx, ax
    mov    ax, 4200h
    xor    cx, cx
    int    21h            ;; seek to offset
    push    ax
    mov    dx, sp
    push    ss
    pop    ds
    mov    cx, 2
    mov    ah, 3fh
    int    21h            ;; read to word buf on stack
    pop    ax            ;; pop word for return
    ret
getWord ENDP

;;======================================================================
;;Read in the fixup table
;;
readFixupTable PROC
    mov    ah, 62h            ;; get psp
    int    21h
    mov    es, bx
    mov    es, es:[2ch]        ;; get environment
    xor    bx, bx
chkForEnd:
    cmp    word ptr es:[bx], 0
    je    foundEnvEnd
    inc    bx
    jmp    chkForEnd
foundEnvEnd:
    add    bx, 4
    push    ds
    push    es
    pop    ds
    mov    dx, bx
    mov    ax, 3d00h        ;; open this exe file
    int    21h
    pop    ds
    jc    rFTfail
    mov    bx, ax            ;; handle to bx

    mov    ax, 0
    call    getWord
    cmp    ax, 'ZM'        ;; quit if not exe signature
    push    ax
    jne    rFTclose
    pop    ax

    mov    ax, relocCountOffset
    call    getWord            ;; get reloc count to cx
    mov    cx, ax

    or    cx, cx
    jnz    getTable
    push    cx
    jmp    rFTclose

getTable:
    mov    ax, relocTableStart
    call    getWord            ;; get start of reloc table

    push    cx            ;; save count
    xor    cx, cx
    mov    dx, ax
    mov    ax, 4200h        ;; seek to reloc table
    int    21h
    pop    cx
    jc    rFTfail

    shl    cx, 2            ;; each entry four bytes
    add    cx, 0fh            ;; round up to para
    shr    cx, 4            ;; cx = paras needed for table

    push    cx            ;; save para count
    push    bx            ;; save handle
    mov    bx, cx            ;; get a buffer from DOS
    mov    ah, 48h
    int    21h
    pop    bx
    pop    cx
    jc    rFTfail

    push    ds
    mov    ds, ax
    mov    es, ax            ;; es is para of table
    xor    dx, dx
    shl    cx, 4            ;; para to byte
    mov    ah, 3fh
    int    21h            ;; read reloc table
    pop    ds
    jc    rFTfail

    mov    ax, relocCountOffset
    call    getWord
    push    ax

rFTclose:
    mov    ah, 3eh
    int    21h            ;; close the file
    pop    ax            ;; pop count of relocs
    jmp    short rFTexit

rFTfail:
    xor    ax, ax
rFTexit:
    ret
readFixupTable ENDP


;;======================================================================
;; Initialize the fixup data area
;;
setupFixup PROC C USES AX BX CX DX
    mov    ax, 0000h        ;; get a descriptor
    int    31h
    mov    fixupSel, ax

    mov    dx, 0ffffh
    mov    cx, 0
    mov    bx, ax
    mov    ax, 0008h        ;; set limit to 64 kb
    int    31h

    mov    ax, 0006h        ;; get segment base
    mov    bx, cs
    int    31h
    shr    dx, 4            ;; convert linear base to para
    shl    cx, 12
    or    dx, cx
    mov    codePara, dx

    mov    ax, 0006h        ;; get segment base
    mov    bx, ds
    int    31h
    shr    dx, 4            ;; convert linear base to para
    shl    cx, 12
    or    dx, cx
    mov    dataPara, dx

    ret
setupFixup ENDP

;;======================================================================
;; Process a fixup
;;
;; es:di points to fixup record
;;
processFixup PROC USES CX ES
    mov    bx, es:[di]        ;; pick up fixup rec in ax bx
    mov    dx, es:[di].2
    add    dx, codePara
    mov    ax, dx            ;; compute linear address
    shl    ax, 4
    shr    dx, 12
    add    ax, bx
    adc    dx, 0            ;; linear addr of fixup in dx:ax
    mov    bx, fixupSel
    mov    cx, dx
    mov    dx, ax
    mov    ax, 7            ;; target descriptor to fixup
    int    31h
    mov    es, bx
    mov    ax, es:[0]        ;; get fixup target
    cmp    ax, codePara        ;; is it a fixup to CS?
    je    fixCode
    cmp    ax, dataPara        ;; a fixup to DS?
    jb    newCode
    je    fixData
    jmp    newData

fixCode:
    mov    es:[0], cs
    jmp    pFexit

fixData:
    mov    es:[0], ds
    jmp    pFexit

newCode:
    mov    bx, ax            ;; para to selector
    mov    ax, 0002h
    int    31h

    mov    bx, ax            ;; create an alias
    mov    ax, 0ah
    int    31h

    mov    bx, ax            ;; set arb to code
    lar    cx, ax
    shr    cx, 8
    or    cx, 8

    mov    ax, 9
    int    31h

    mov    es:[0], bx
    jmp    pFexit

newData:
    mov    bx, ax            ;; para to selector
    mov    ax, 0002h
    int    31h
    mov    es:[0], ax
    jmp    pFexit

pFexit:
    ret
processFixup ENDP


;;======================================================================
;; Main routine for fixup
;;
;;
_fixup    PROC C  USES DI
    call    readFixupTable        ;; rets count in ax, table in es
    or    ax, ax
    jz    fixupExit

    call    setupFixup

    mov    cx, ax
    xor     di, di
nextFU:
    call    processFixup
    add    di, 4
    loop    nextFU

    mov    ax, 1            ;; free descriptor
    mov    bx, fixupSel
    int    31h

    mov    ah, 49h
    int    21h
fixupExit:
    ret
_fixup    ENDP

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;         Exception handlers
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; Macro to output a string
puts     MACRO str
    local over, slbl
    jmp    short over
slbl    db    str, '$'
over:
    lea    dx, slbl
    mov    ah, 9
    int    21h
    ENDM

;; Macro to output a hex value
hexOut    MACRO val
    mov    cx, val
    call    putHex
    ENDM

;; Macro to output a string followed by a hex value
putReg    MACRO str, r
    puts    str
    mov    cx, r
    call    putHex
    ENDM

;; Hex output routine
hexdigs    db "0123456789ABCDEF"
putHex    PROC USES BX             ;; output CX in hex
    mov    bx, cx            ;;   use bx as working reg
    shr    bx, 12            ;;   top nibble to right
    mov    dl, hexdigs[bx]        ;;   look up character
    mov    ah, 2            ;;   send to DOS
    int    21h

    mov    bx, cx            ;; original value to bx
    shr    bx, 8            ;; 2nd nibble to right
    and    bx, 0fh            ;; mask off unwanted higher nibble
    mov    dl, hexdigs[bx]        ;; look up character
    mov    ah, 2            ;; send to DOS
    int    21h

    mov    bx, cx            ;; etc.
    shr    bx, 4
    and    bx, 0fh
    mov    dl, hexdigs[bx]
    mov    ah, 2
    int    21h

    mov    bx, cx
    and    bx, 0fh
    mov    dl, hexdigs[bx]
    mov    ah, 2
    int    21h

    ret
putHex    ENDP

;; Exception handler entry points
;;
;; This macro generates the exception handlers, each of which pushes
;; its ordinal value and jumps to the generic handler
;;
    IRP n, <00,01,02,03,04,05,06,07,08,09,0A,0B,0C,0D,0E,0F>
_exc&n&Handler:
    push    &n&H
    jmp    near ptr exceptionEntry
    ENDM
;;
;; Exception names - the generic handler uses this table to look up
;; the name of the exception that occurred
;;
x00nm    db    "Divide by Zero$"
x01nm    db    "Trace$"
x02nm    db    "?$"
x03nm    db    "Breakpoint$"
x04nm    db    "Overflow$"
x05nm    db    "Bounds$"
x06nm    db    "Invalid Opcode$"
x07nm    db    "Coprocessor (7)$"
x08nm    db    "Double Fault$"
x09nm    db    "Coprocessor (9)$"
x0anm    db    "Invalid TSS$"
x0bnm    db    "Segment not present$"
x0cnm    db    "Stack$"
x0dnm    db    "General Protection$"
x0enm    db    "Page Fault$"
x0fnm    db    "?$"
x10nm    db    "Coprocessor (16)$"

xNameTable:
    IRP n, <00,01,02,03,04,05,06,07,08,09,0A,0B,0C,0D,0E,0F>
    dw    offset x&n&nm
    ENDM

;;
;; Exception entry point table - this table contains the offset of each
;; handler - used to hook the vectors.
;;
xEntryTable:
    IRP n, <00,01,02,03,04,05,06,07,08,09,0A,0B,0C,0D,0E,0F>
    dw    offset _exc&n&Handler
    ENDM

;;
;; Install the default exception handlers for fatal exceptions
;;
_installHandlers PROC USES SI DI
    lea    si, xEntryTable
    xor    di, di
_iHhook:
    IRP n, <0, 1, 2, 3, 4, 5, 7>    ;; don't handle these - DPMI is
      cmp    di, n            ;; supposed to pass them through
      je    _iHnext            ;; to real mode
    ENDM

    mov    ax, 203h        ;; set exception handler service
    mov    bx, di
    mov    cx, cs
    mov    dx, cs:[si]
    int    31h

_iHnext:
    add    si, 2
    inc    di
    cmp    di, 10h
    jne    _iHhook

    ret
_installHandlers ENDP


;; This structure defines the register structure in effect while the
;; generic handler runs
;;
eFrame STRUC
    efDS    dw    ?
    efES    dw    ?
    efDI    dw    ?
    efSI    dw    ?
    efBP    dw    ?
    efXX    dw    ?
    efBX    dw    ?
    efDX    dw    ?
    efCX    dw    ?
    efAX    dw    ?
    efxNum    dw    ?
    efhRIP    dw    ?
    efhRCS    dw    ?
    efError    dw    ?
    efXIP    dw    ?
    efXCS    dw    ?
    efXFl    dw    ?
    efXSP    dw    ?
    efXSS    dw    ?
eFrame ENDS

;;
;; The generic handler - dump registers and exit
;;
exceptionEntry PROC
    pusha                    ;; build frame
    push    es
    push    ds
    mov    bp, sp

    push    cs                ;; ds <- cs
    pop    ds

    mov    bx, [bp].efxNum            ;; get exception number
    shl    bx, 1                ;; make it word offset
    add    bx, offset xNameTable        ;; look up name of exception
    mov    dx, [bx]

    mov    ah, 9                ;; output it to  DOS
    int    21h

    putReg    " Exception at ", [bp].efXCS    ;; dump regs
    putReg    ":",efXIP
    putReg    " Error code=", [bp].efError
    puts    <10,13>

    putReg    "SS=", [bp].efXSS
    putReg    " SP=", [bp].efXSP
    putReg    " DS=", [bp].efDS
    putReg    " ES=", [bp].efES
    putReg    " Flags=", [bp].efXFl

    puts    <10,13>
    putReg    "AX=", [bp].efAX
    putReg    " BX=", [bp].efBX
    putReg    " CX=", [bp].efCX
    putReg    " DX=", [bp].efDX
    putReg    " SI=", [bp].efSI
    putReg    " DI=", [bp].efDI
    putReg    " BP=", [bp].efBP
    puts    <10,13>

    mov    [bp].efXCS, cs                ;; set frame to exit
    mov    [bp].efXIP, offset bye
    pop    ds
    pop    es
    popa
    add    sp, 2
    retf                        ;; get off host stack

bye:
    mov    ah, 4Ch                    ;; and terminate
    int    21h
exceptionEntry ENDP

    end