806 lines
17 KiB
NASM
806 lines
17 KiB
NASM
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PAGE ,132
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TITLE DXROM.ASM -- Dos Extender ROM Specific Code
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; Copyright (c) Microsoft Corporation 1990-1991. All Rights Reserved.
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;***********************************************************************
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;
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; DXROM.ASM -- Dos Extender ROM Specific Code
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;
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;-----------------------------------------------------------------------
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;
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; This module contains code specific to the ROM version of the DOS
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; Extender.
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;
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;-----------------------------------------------------------------------
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;
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; 11/05/90 jimmat Created.
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;
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;***********************************************************************
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.286p
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IFDEF ROM
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; -------------------------------------------------------
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; INCLUDE FILE DEFINITIONS
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; -------------------------------------------------------
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.xlist
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.sall
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include segdefs.inc
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include gendefs.inc
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include pmdefs.inc
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include dxrom.inc
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.list
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; -------------------------------------------------------
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; GENERAL SYMBOL DEFINITIONS
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; -------------------------------------------------------
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; Define some pubilc symbols to be exported for the ROM Image Builder
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public __selDXCODE, __selDXDGROUP, __selDXPMCODE
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__selDXCODE = SEL_DXCODE
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__selDXDGROUP = SEL_DXDATA
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__selDXPMCODE = SEL_DXPMCODE
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public __selFirstLDT, __selLDTAlias
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__selFirstLDT = SEL_USER
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__selLDTAlias = SEL_LDT_ALIAS
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; -------------------------------------------------------
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; EXTERNAL SYMBOL DEFINITIONS
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; -------------------------------------------------------
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extrn ParaToLinear:NEAR
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extrn AllocateLDTSelector:NEAR
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extrn ChildTerminationHandler:NEAR
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externFP NSetSegmentDscr
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; -------------------------------------------------------
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; DATA SEGMENT DEFINITIONS
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; -------------------------------------------------------
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DXDATA segment
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extrn selGDTFree:WORD
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extrn segDXData:WORD
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extrn ExitCode:BYTE
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SaveROMVector dw ?
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cparChildMem dw ? ; size of child DOS mem block in para's
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regOurSSSP dd ? ; SS:SP save location
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DXDATA ends
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; -------------------------------------------------------
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; CODE SEGMENT VARIABLES
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; -------------------------------------------------------
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DXCODE segment
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; For the ROM version, the following items locate (and size) the
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; DGROUP and DXPMCODE segments. These items are 'imported' from
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; the ROM Image Builder which sets the values when the ROM image
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; is created.
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extrn lmaDXDGROUP:DWORD, cparDXDGROUP:ABS, lmaDXPMCODE:DWORD
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public lmaRomDXPMCode
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cparDgroup dw cparDXDGROUP
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lmaDGroup dd lmaDXDGROUP
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lmaRomDXPMCode dd lmaDXPMCODE
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DXCODE ends
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DXPMCODE segment
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extrn selDgroupPM:WORD
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extrn lmaROMTOC:DWORD
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MyLmaROMTOC dd lmaROMTOC
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DXPMCODE ends
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; -------------------------------------------------------
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subttl ROM Real Mode ROM Specific Routines
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page
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; -------------------------------------------------------
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; ROM REAL MODE ROM SPECIFIC ROUTINES
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; -------------------------------------------------------
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DXCODE segment
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assume cs:DXCODE
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; -------------------------------------------------------
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; ROMEntry -- Setup the special ROM environment needed
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; immediately by DOSX.
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;
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; Note: This routine runs in real mode only!
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;
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; Input: ES -> PSP for use by DOSX
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; Output: CY clear if successful, set if init failed
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; DS -> DOSX RAM DGROUP
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; DX:AX = far return address to app that invoked DOSX
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; Errors: none
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; Uses: All except ES
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assume ds:NOTHING,es:NOTHING,ss:NOTHING
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public ROMEntry
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ROMEntry proc near
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; Allocate a data segment in RAM and copy down the ROM version
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mov ah,48h ;allocate RAM for DGROUP
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mov bx,cparDgroup
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int 21h
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jc REAllocFailed ;big trouble if this happens
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push ax ;save RAM DGROUP
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mov dx, word ptr lmaDGroup[0]
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mov bx, word ptr lmaDGroup[2]
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mov cx, 4
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xor si, si
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@@:
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shr bx, 1 ;determine if its in conventional
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rcr dx, 1 ;memory and if so the canonical
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rcr si, 1 ;segment:offset in dx:si
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loop @B
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or bx, bx
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jnz RECopyFromExtended
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RECopyFromConventional:
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push es ;save es
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mov es,ax
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mov ds,dx
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mov cx,cparDgroup ; (CS variable)
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shl cx,3 ;DGROUP size in words
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xor di,di
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cld
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rep movsw
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pop es ;restore es
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pop ds ;point to RAM dgroup
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assume ds:DGROUP, es:NOTHING
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clc ;worked!
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REAllocFailed:
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ret
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RECopyFromExtended:
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sub sp, 30h
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mov si, sp
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push ss
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pop es
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mov di, si
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push ax
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xor ax,ax
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mov cx, 18h
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rep stosw
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dec ax
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mov es:[si+10h], ax ; Limits to FFFF
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mov es:[si+18h], ax
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mov al, 93h
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mov es:[si+15h], al ; access to data rw
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mov es:[si+1Dh], al
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pop ax
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mov cx, 4
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sub dx, dx
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@@:
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shl ax, 1 ;compute new DGROUP lma
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rcl dx, 1
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loop @B
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mov es:[si+1Ah], ax ;stuff into dest descr
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mov es:[si+1Ch], dl
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mov ax, word ptr lmaDGroup[0]
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mov dx, word ptr lmaDGroup[2]
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mov es:[si+12h], ax
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mov es:[si+14h], dl ;put ROM lma in source descr
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mov cx, cparDGroup
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shl cx, 3 ;length of dgroup ***in words ***
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mov ah, 87h ;fn 87h = copy extended memory
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int 15h
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jc REExtCopyFailed
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add sp, 30h
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pop ds ;get ram address in ds
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clc
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ret
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REExtCopyFailed:
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add sp, 32h ;remove stuff from stack
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stc
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ret
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ROMEntry endp
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; -------------------------------------------------------
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; InvokeROMChild -- ROM specific method of invoking the
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; child application.
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;
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; Note: This routine must be called in real mode!
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; It returns to the caller after the child returns. Control
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; passes directly to ChildTerminationHandler if child does a
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; DOS exit call.
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;
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; Input: none
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; Output: CY clear if child executed successfully, set if failed
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; AX = error code if failure (8 = insufficient DOS memory)
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; Errors: none
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; Uses: All except DS
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assume ds:DGROUP,es:NOTHING,ss:NOTHING
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public InvokeROMChild
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InvokeROMChild proc near
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; Setup the environment for the ROM child app. First, allocate
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; the largest conventional memory block available and build a PSP
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; at the start of it.
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mov bx,-1 ; how big is the largest avail block?
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dossvc 48h
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cmp bx,64 SHL 6 ; is there at least 64k available?
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jae @f
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mov ax,8 ; DOS insufficient memory error
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jmp short IRCFail
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@@:
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mov cparChildMem,bx ; save block size
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dossvc 48h ; allocate block
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IF DEBUG
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jnc @f ; shouldn't fail, but...
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int 3
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@@:
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ENDIF
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; Got conventional memory, now build a PSP at the start of it.
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mov dx,ax ; new PSP here
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mov si,10h ; use this as mem length for now
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dossvc 55h ; duplicate PSP call
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; Set up the termination vector in the child's PSP to point to
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; the Dos Extender termination code.
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mov es,dx
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assume es:PSPSEG
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mov word ptr [lpfnParent],offset ChildTerminationHandler
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mov word ptr [lpfnParent+2],cs
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; Switch to protected mode to complete initialization of child environment
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SwitchToProtectedMode
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assume ds:DGROUP,es:DGROUP
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sti
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; Allocate/init a selector mapping first 64k of child memory block & PSP
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call AllocateLDTSelector ; get new selector in AX
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; DX still has PSP segment,
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call ParaToLinear ; convert to linear memory address
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push bx ; save lma for later
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push dx
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push ax ; save mem/PSP selector too
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cCall NSetSegmentDscr,<ax,bx,dx,0,0FFFFh,STD_DATA>
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; Allocate/init a zero length selector pointing to just past the end of
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; the child's memory block and plug the selector into the PSP.
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call AllocateLDTSelector ; get another selector
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pop es
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assume es:PSPSEG
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mov segMemEnd,ax ; store in child's PSP
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mov dx,cparChildMem ; get size of memory block in bytes
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call ParaToLinear ; in BX:DX
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pop ax ; recover lma of block start
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pop cx ; in CX:AX
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add dx,ax
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adc bx,cx ; BX:DX = lma of block end
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cCall NSetSegmentDscr,<segMemEnd,bx,dx,0,0,STD_DATA>
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; Allocate/init a selector pointin to our DOS environment block--plug this
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; into the child's PSP so it can party on the same env block.
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call AllocateLDTSelector
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mov dx,segEnviron ; segment from PSP
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call ParaToLinear
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cCall NSetSegmentDscr,<ax,bx,dx,0,7FFFH,STD_DATA>
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mov segEnviron,ax ; selector to PSP
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; The child environment is now build, invoke the child with DS = ES =
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; memory/PSP block. Set the stack 64k (less one word) into the block,
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; push our far return address on the stack.
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mov word ptr [regOurSSSP],sp ;save DOSX stack location
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mov word ptr [regOurSSSP+2],ss
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mov ax,es ; switch to child stack
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mov ss,ax
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mov sp,0FFFEh
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push cs ; far return address to us
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push offset IRCReturn
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call GetROMTOCPointer ; push the kernel entry CS:IP on stack
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assume es:ROMTOC
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push word ptr [KRNL_CSIP+2]
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push word ptr [KRNL_CSIP]
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mov ds,ax
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mov es,ax
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assume ds:NOTHING,es:NOTHING
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xor cx, cx ; tell KRNL386 linear == physical
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xor dx, dx
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retf ; invoke the kernel
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public IRCReturn ;public for debugging
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IRCReturn:
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mov ds,selDgroupPM ; restore our DS
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assume ds:DGROUP
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mov ss,word ptr [regOurSSSP+2] ; and our stack
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mov sp,word ptr [regOurSSSP]
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mov ExitCode,al ; save the child exit code
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SwitchToRealMode
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sti
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clc
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ret
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IRCFail:
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stc
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ret
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InvokeROMChild endp
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; -------------------------------------------------------
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; ROMInitialization -- This routine performs the initial ROM
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; specific DOS Extender initialization.
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;
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; Note: This routine runs in real mode only!
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;
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; Input: none
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; Output: CY clear if successful, set if init failed
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; Errors: none
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; Uses: AX
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assume ds:DGROUP,es:NOTHING,ss:NOTHING
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public ROMInitialization
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ROMInitialization proc near
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; Point 2nd word of DOSX ROM Int vector to the data segment.
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push es
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xor ax,ax
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mov es,ax
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mov ax, word ptr es:[ROMIntVector*4][2] ;save current vector
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mov SaveROMVector,ax ; contents
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mov word ptr es:[ROMIntVector*4][2],ds ;point vector to data
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pop es
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clc
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ROMInitFailed:
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ret
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|
||
|
|
ROMInitialization endp
|
||
|
|
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; ROMCleanUp -- This routine performs the ROM specific
|
||
|
|
; DOS Extender termination clean up.
|
||
|
|
;
|
||
|
|
; Note: This routine runs in real mode only!
|
||
|
|
;
|
||
|
|
; Input: none
|
||
|
|
; Output: none
|
||
|
|
; Errors: none
|
||
|
|
; Uses: none
|
||
|
|
|
||
|
|
assume ds:DGROUP,es:NOTHING,ss:NOTHING
|
||
|
|
public ROMCleanUp
|
||
|
|
|
||
|
|
ROMCleanUp proc near
|
||
|
|
|
||
|
|
; Remove DOSX Int vector pointer to the data segment.
|
||
|
|
|
||
|
|
push es
|
||
|
|
xor ax,ax
|
||
|
|
mov es,ax
|
||
|
|
|
||
|
|
mov ax,SaveROMVector ;restore prior contents
|
||
|
|
mov word ptr es:[ROMIntVector*4][2],ax
|
||
|
|
|
||
|
|
pop es
|
||
|
|
|
||
|
|
ret
|
||
|
|
|
||
|
|
ROMCleanUp endp
|
||
|
|
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
subttl ROM Real Mode Utility Routines
|
||
|
|
page
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; ROM REAL MODE UTILITY ROUTINES
|
||
|
|
; -------------------------------------------------------
|
||
|
|
|
||
|
|
; GetDXDataRM -- This routine returns the paragraph address of
|
||
|
|
; the DOS Extender data segment. It should only be called
|
||
|
|
; by real mode code.
|
||
|
|
;
|
||
|
|
; Input: none
|
||
|
|
; Output: AX = DOSX data segment paragraph address
|
||
|
|
; Errors: none
|
||
|
|
; Uses: none
|
||
|
|
|
||
|
|
assume ds:NOTHING,es:NOTHING,ss:NOTHING
|
||
|
|
public GetDXDataRM
|
||
|
|
|
||
|
|
GetDXDataRM proc near
|
||
|
|
|
||
|
|
; Get data segment value from 2nd word of DOSX Int vector
|
||
|
|
|
||
|
|
push ds
|
||
|
|
|
||
|
|
xor ax,ax
|
||
|
|
mov ds,ax
|
||
|
|
mov ax,word ptr ds:[ROMIntVector*4][2]
|
||
|
|
|
||
|
|
IF DEBUG
|
||
|
|
mov ds,ax
|
||
|
|
cmp ax,ds:[segDXData] ; Make sure ax points to the
|
||
|
|
jz @f ; right place
|
||
|
|
int 3
|
||
|
|
@@:
|
||
|
|
ENDIF
|
||
|
|
pop ds
|
||
|
|
ret
|
||
|
|
|
||
|
|
GetDXDataRM endp
|
||
|
|
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; SetDXDataRM -- This routine sets DS equal to the DOS Extender
|
||
|
|
; data segment address. It should only be called by real
|
||
|
|
; mode code.
|
||
|
|
;
|
||
|
|
; Input: none
|
||
|
|
; Output: DS -> DOSX data segment
|
||
|
|
; Errors: none
|
||
|
|
; Uses: none
|
||
|
|
|
||
|
|
assume ds:NOTHING,es:NOTHING,ss:NOTHING
|
||
|
|
public SetDXDataRM
|
||
|
|
|
||
|
|
SetDXDataRM proc near
|
||
|
|
|
||
|
|
; Get data segment value from 2nd word of DOSX Int vector
|
||
|
|
|
||
|
|
push ax
|
||
|
|
|
||
|
|
xor ax,ax
|
||
|
|
mov ds,ax
|
||
|
|
mov ds,word ptr ds:[ROMIntVector*4][2]
|
||
|
|
|
||
|
|
IF DEBUG
|
||
|
|
mov ax,ds ; Make sure DS points to the
|
||
|
|
cmp ax,ds:[segDXData] ; right place
|
||
|
|
jz @f
|
||
|
|
int 3
|
||
|
|
@@:
|
||
|
|
ENDIF
|
||
|
|
pop ax
|
||
|
|
ret
|
||
|
|
|
||
|
|
SetDXDataRM endp
|
||
|
|
|
||
|
|
|
||
|
|
DXCODE ends
|
||
|
|
|
||
|
|
;****************************************************************
|
||
|
|
|
||
|
|
DXPMCODE SEGMENT
|
||
|
|
assume cs:DXPMCODE
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
subttl ROM Protect Mode Utility Routines
|
||
|
|
page
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; ROM PROTECT MODE UTILITY ROUTINES
|
||
|
|
; -------------------------------------------------------
|
||
|
|
|
||
|
|
; ROMInitLDT -- This routine initializes the LDT descriptors
|
||
|
|
; defined in the ROM prototype LDT.
|
||
|
|
;
|
||
|
|
; Input: none
|
||
|
|
; Output: none
|
||
|
|
; Errors: none
|
||
|
|
; Uses: none
|
||
|
|
|
||
|
|
assume ds:DGROUP,es:NOTHING,ss:NOTHING
|
||
|
|
public ROMInitLDT
|
||
|
|
|
||
|
|
ROMInitLDT proc near
|
||
|
|
|
||
|
|
; Access the ROM Table of Contents to find out where the proto LDT
|
||
|
|
; is, and how many descriptors it contains.
|
||
|
|
|
||
|
|
pusha
|
||
|
|
push ds
|
||
|
|
push es
|
||
|
|
|
||
|
|
call GetROMTOCPointer ; Note: uses SEL_SCR0
|
||
|
|
assume es:ROMTOC
|
||
|
|
|
||
|
|
mov cx,cROMsels ; # descriptors defined in proto LDT
|
||
|
|
mov bx,word ptr [lmaROMLDT+2]
|
||
|
|
mov dx,word ptr [lmaROMLDT] ; bx:dx = lma of proto LDT
|
||
|
|
mov ax,FirstROMSel
|
||
|
|
mov di, ax
|
||
|
|
|
||
|
|
; Do a quick (and dirty?) allocation of the correct number of LDT selectors.
|
||
|
|
; DANGER: this code has intimate knowledge of how the LDT free list is kept!
|
||
|
|
; We could make CX calls to AllocateLDTSelector, but that is slow and would
|
||
|
|
; do zillions and zillions of segment loads.
|
||
|
|
;
|
||
|
|
cmp ax,selGDTFree ; next free descriptor in LDT
|
||
|
|
jne alloc_in_chain
|
||
|
|
|
||
|
|
IF DEBUG
|
||
|
|
cmp ax,__selFirstLDT ; first one free better be the one
|
||
|
|
jz @f ; the ROM Image Builder used.
|
||
|
|
int 3
|
||
|
|
@@:
|
||
|
|
ENDIF
|
||
|
|
shl cx,3 ; 'allocate' all these by setting
|
||
|
|
add ax,cx ; the next free to be beyond them
|
||
|
|
mov selGDTFree,ax
|
||
|
|
push SEL_LDT_ALIAS OR STD_RING
|
||
|
|
pop es
|
||
|
|
jmp short sels_alloced
|
||
|
|
|
||
|
|
alloc_in_chain:
|
||
|
|
mov si, ax
|
||
|
|
sub si, 8
|
||
|
|
push SEL_LDT_ALIAS OR STD_RING
|
||
|
|
pop es
|
||
|
|
shl cx, 3
|
||
|
|
add ax, cx
|
||
|
|
mov es:[si], ax
|
||
|
|
|
||
|
|
sels_alloced:
|
||
|
|
|
||
|
|
; Copy the prototype descriptors into the actual LDT
|
||
|
|
|
||
|
|
cCall NSetSegmentDscr,<SEL_SCR0,bx,dx,0,-1,STD_DATA>
|
||
|
|
|
||
|
|
push SEL_SCR0 OR STD_TBL_RING
|
||
|
|
pop ds ; ds -> proto LDT descriptors
|
||
|
|
assume ds:NOTHING
|
||
|
|
|
||
|
|
xor si,si
|
||
|
|
|
||
|
|
shr cx,1 ; # words of descriptors to copy
|
||
|
|
|
||
|
|
cld
|
||
|
|
rep movsw ; move'm into the LDT
|
||
|
|
|
||
|
|
pop es
|
||
|
|
pop ds
|
||
|
|
assume ds:DGROUP,es:NOTHING
|
||
|
|
popa
|
||
|
|
|
||
|
|
ret
|
||
|
|
|
||
|
|
ROMInitLDT endp
|
||
|
|
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; GetROMTOCPointer -- return ES:0 pointing to the ROM Table of
|
||
|
|
; Contents.
|
||
|
|
;
|
||
|
|
; Note: modifies the SEL_SCR0 descriptor!
|
||
|
|
;
|
||
|
|
; Input: none
|
||
|
|
; Output: ES:0 -> ROM TOC
|
||
|
|
; Errors: none
|
||
|
|
; Uses: none
|
||
|
|
|
||
|
|
assume ds:DGROUP,es:NOTHING,ss:NOTHING
|
||
|
|
public GetROMTOCPointer
|
||
|
|
|
||
|
|
GetROMTOCPointer proc near
|
||
|
|
|
||
|
|
push bx
|
||
|
|
push dx
|
||
|
|
|
||
|
|
mov bx,word ptr [MyLmaROMTOC+2]
|
||
|
|
mov dx,word ptr [MyLmaROMTOC] ;bx:dx = lma of ROMTOC
|
||
|
|
|
||
|
|
cCall NSetSegmentDscr,<SEL_SCR0,bx,dx,0,-1,STD_DATA>
|
||
|
|
|
||
|
|
push SEL_SCR0 OR STD_TBL_RING
|
||
|
|
pop es
|
||
|
|
|
||
|
|
pop dx
|
||
|
|
pop bx
|
||
|
|
|
||
|
|
ret
|
||
|
|
|
||
|
|
GetROMTOCPointer endp
|
||
|
|
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; GetDXDataPM -- This routine returns the paragraph address of
|
||
|
|
; the DOS Extender data segment. It should only be called
|
||
|
|
; by protected mode code.
|
||
|
|
;
|
||
|
|
; Input: none
|
||
|
|
; Output: AX = DOSX data segment paragraph address
|
||
|
|
; Errors: none
|
||
|
|
; Uses: none
|
||
|
|
|
||
|
|
assume ds:NOTHING,es:NOTHING,ss:NOTHING
|
||
|
|
public GetDXDataPM
|
||
|
|
|
||
|
|
GetDXDataPM proc near
|
||
|
|
|
||
|
|
; Get data segment value from 1st word of DOSX Int vector
|
||
|
|
|
||
|
|
push ds
|
||
|
|
|
||
|
|
mov ax,SEL_RMIVT or STD_RING
|
||
|
|
mov ds,ax
|
||
|
|
mov ax,word ptr ds:[ROMIntVector*4][2]
|
||
|
|
|
||
|
|
pop ds
|
||
|
|
ret
|
||
|
|
|
||
|
|
GetDXDataPM endp
|
||
|
|
|
||
|
|
if 0 ;***************************************************************
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; SetDXDataPM -- This routine sets DS equal to the DOS Extender
|
||
|
|
; data segment address. It should only be called by protected
|
||
|
|
; mode code.
|
||
|
|
;
|
||
|
|
; Input: none
|
||
|
|
; Output: DS -> DOSX data segment
|
||
|
|
; Errors: none
|
||
|
|
; Uses: none
|
||
|
|
|
||
|
|
assume ds:NOTHING,es:NOTHING,ss:NOTHING
|
||
|
|
public SetDXDataPM
|
||
|
|
|
||
|
|
SetDXDataPM proc near
|
||
|
|
|
||
|
|
; Set DS = data segment selector.
|
||
|
|
|
||
|
|
push SEL_DXDATA OR STD_RING
|
||
|
|
pop ds
|
||
|
|
ret
|
||
|
|
|
||
|
|
SetDXDataPM endp
|
||
|
|
endif ;***************************************************************
|
||
|
|
|
||
|
|
|
||
|
|
DXPMCODE ends
|
||
|
|
|
||
|
|
;****************************************************************
|
||
|
|
|
||
|
|
ifdef ROMSTUB ;--------------------------------------------------------
|
||
|
|
|
||
|
|
*********************************************
|
||
|
|
*********************************************
|
||
|
|
***** *****
|
||
|
|
***** THIS CODE IS NO LONGER USED *****
|
||
|
|
***** *****
|
||
|
|
*********************************************
|
||
|
|
*********************************************
|
||
|
|
|
||
|
|
DXSTUB SEGMENT
|
||
|
|
assume cs:DXSTUB
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
subttl Real Mode RAM Stub Segment
|
||
|
|
page
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; REAL MODE RAM STUB SEGMENT
|
||
|
|
; -------------------------------------------------------
|
||
|
|
|
||
|
|
; This segment contains code and data that is moved to conventional
|
||
|
|
; RAM during initialization. The code is only executed from RAM
|
||
|
|
; mode and exists for those few cases where it is most convenient
|
||
|
|
; to have code segement variables.
|
||
|
|
;
|
||
|
|
; Note: Since this code is moved to RAM, be very carefull of the
|
||
|
|
; instructions it contains. In particular, realize the the code segment
|
||
|
|
; value is going to be different from the copy in ROM.
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; CODE SEGMENT VARIABLES
|
||
|
|
; -------------------------------------------------------
|
||
|
|
|
||
|
|
public PrevInt2FHandler
|
||
|
|
|
||
|
|
PrevInt2FHandler dd ?
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
; StubInt2FHook -- This code is used by the DOS Extender real mode
|
||
|
|
; Int 2Fh hook to chain the interrupt to the previous Int 2Fh
|
||
|
|
; handler.
|
||
|
|
;
|
||
|
|
; Note: This code executes in real mode only!
|
||
|
|
;
|
||
|
|
; Input: stack = [DS] [IP] [CS] [FL]
|
||
|
|
; Output: none
|
||
|
|
; Errors: none
|
||
|
|
; Uses: none
|
||
|
|
|
||
|
|
|
||
|
|
assume ds:NOTHING,es:NOTHING,ss:NOTHING
|
||
|
|
public StubInt2FHook
|
||
|
|
|
||
|
|
StubInt2FHook proc far
|
||
|
|
|
||
|
|
pop ds
|
||
|
|
jmp [PrevInt2FHandler]
|
||
|
|
|
||
|
|
StubInt2FHook endp
|
||
|
|
|
||
|
|
; -------------------------------------------------------
|
||
|
|
|
||
|
|
DXSTUB ends
|
||
|
|
|
||
|
|
endif ;----------------------------------------------------------------
|
||
|
|
|
||
|
|
;****************************************************************
|
||
|
|
|
||
|
|
ENDIF ;ROM
|
||
|
|
|
||
|
|
end
|