61d87d82bb
variables where necessary. This clears up the confusing shadowing. git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@716 6ac86273-5f31-0410-b378-82cca8765d1b
956 lines
31 KiB
NASM
956 lines
31 KiB
NASM
;
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; File:
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; kernel.asm
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; Description:
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; kernel start-up code
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;
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; Copyright (c) 1995, 1996
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; Pasquale J. Villani
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; All Rights Reserved
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;
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; This file is part of DOS-C.
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;
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; DOS-C is free software; you can redistribute it and/or
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; modify it under the terms of the GNU General Public License
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; as published by the Free Software Foundation; either version
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; 2, or (at your option) any later version.
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;
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; DOS-C is distributed in the hope that it will be useful, but
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; WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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; the GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public
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; License along with DOS-C; see the file COPYING. If not,
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; write to the Free Software Foundation, 675 Mass Ave,
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; Cambridge, MA 02139, USA.
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;
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; $Id$
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;
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%include "segs.inc"
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%include "ludivmul.inc"
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segment PSP
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extern _ReqPktPtr:wrt LGROUP
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STACK_SIZE equ 384/2 ; stack allocated in words
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;************************************************************
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; KERNEL BEGINS HERE, i.e. this is byte 0 of KERNEL.SYS
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;************************************************************
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..start:
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entry:
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jmp short realentry
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;************************************************************
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; KERNEL CONFIGURATION AREA
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; this is copied up on the very beginning
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; it's a good idea to keep this in sync with KConfig.h
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;************************************************************
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global _LowKernelConfig
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_LowKernelConfig:
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db 'CONFIG' ; constant
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dw configend-configstart; size of config area
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; to be checked !!!
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configstart:
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DLASortByDriveNo db 0 ; sort disks by drive order
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InitDiskShowDriveAssignment db 1 ;
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SkipConfigSeconds db 2 ;
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ForceLBA db 0 ;
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GlobalEnableLBAsupport db 1 ;
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BootHarddiskSeconds db 0 ;
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configend:
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;************************************************************
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; KERNEL CONFIGURATION AREA END
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;************************************************************
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;************************************************************
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; KERNEL real entry (at ~60:20)
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;
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; moves the INIT part of kernel.sys to high memory (~9000:0)
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; then jumps there
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; to aid debugging, some '123' messages are output
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; this area is discardable and used as temporary PSP for the
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; init sequence
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;************************************************************
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realentry: ; execution continues here
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push ax
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push bx
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pushf
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mov ax, 0e31h ; '1' Tracecode - kernel entered
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mov bx, 00f0h
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int 010h
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popf
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pop bx
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pop ax
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jmp far kernel_start
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beyond_entry: resb 256-(beyond_entry-entry)
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; scratch area for data (DOS_PSP)
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segment INIT_TEXT
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extern _FreeDOSmain
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;
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; kernel start-up
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;
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kernel_start:
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push ax
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push bx
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pushf
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mov ax, 0e32h ; '2' Tracecode - kernel entered
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mov bx, 00f0h
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int 010h
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popf
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pop bx
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pop ax
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mov ax,cs
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cli
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mov ss,ax
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mov sp,init_tos
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int 12h ; move the init code to higher memory
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mov cl,6
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shl ax,cl
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mov dx,init_end+15
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mov cl,4
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shr dx,cl
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sub ax,dx
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mov es,ax
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mov ax,cs
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mov ds,ax
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xor si,si
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xor di,di
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mov cx,init_end+1
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shr cx,1
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cld
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rep movsw
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push es
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mov ax,cont
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push ax
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retf
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cont: mov ax,cs
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mov ss,ax
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; Now set up call frame
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mov ds,[cs:_INIT_DGROUP]
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mov bp,sp ; and set up stack frame for c
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sti ; now enable them
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push ax
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push bx
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pushf
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mov ax, 0e33h ; '3' Tracecode - kernel entered
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mov bx, 00f0h
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int 010h
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popf
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pop bx
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pop ax
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mov byte [_BootDrive],bl ; tell where we came from
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;!! int 11h
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;!! mov cl,6
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;!! shr al,cl
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;!! inc al
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;!! mov byte [_NumFloppies],al ; and how many
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mov ax,ss
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mov ds,ax
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mov es,ax
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jmp _FreeDOSmain
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%ifdef WATCOM
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global _IU4M
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_IU4M:
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LMULU
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global _IU4D
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_IU4D:
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LDIVMODU
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%endif
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segment INIT_TEXT_END
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;************************************************************
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; KERNEL CODE AREA END
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; the NUL device
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;************************************************************
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segment CONST
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;
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; NUL device strategy
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;
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global _nul_strtgy
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_nul_strtgy:
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mov word [cs:_ReqPktPtr],bx ;save rq headr
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mov word [cs:_ReqPktPtr+2],es
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retf
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;
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; NUL device interrupt
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;
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global _nul_intr
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_nul_intr:
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push es
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push bx
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les bx,[cs:_ReqPktPtr] ;es:bx--> rqheadr
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or word [es:bx+3],100h ;set "done" flag
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pop bx
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pop es
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retf
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segment _LOWTEXT
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; floppy parameter table
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global _int1e_table
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_int1e_table: times 0eh db 0
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;************************************************************
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; KERNEL FIXED DATA AREA
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;************************************************************
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segment _FIXED_DATA
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; Because of the following bytes of data, THIS MODULE MUST BE THE FIRST
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; IN THE LINK SEQUENCE. THE BYTE AT DS:0004 determines the SDA format in
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; use. A 0 indicates MS-DOS 3.X style, a 1 indicates MS-DOS 4.0-6.X style.
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global DATASTART
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DATASTART:
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global _DATASTART
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_DATASTART:
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dos_data db 0
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dw kernel_start
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db 0 ; padding
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dw 1 ; Hardcoded MS-DOS 4.0+ style
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times (0eh - ($ - DATASTART)) db 0
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global _NetBios
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_NetBios dw 0 ; NetBios Number
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times (26h - 0ch - ($ - DATASTART)) db 0
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; Globally referenced variables - WARNING: DO NOT CHANGE ORDER
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; BECAUSE THEY ARE DOCUMENTED AS UNDOCUMENTED (?) AND HAVE
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; MANY MULTIPLEX PROGRAMS AND TSR'S ACCESSING THEM
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global _NetRetry
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_NetRetry dw 3 ;-000c network retry count
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global _NetDelay
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_NetDelay dw 1 ;-000a network delay count
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global _DskBuffer
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_DskBuffer dd -1 ;-0008 current dos disk buffer
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global _inputptr
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_inputptr dw 0 ;-0004 Unread con input
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global _first_mcb
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_first_mcb dw 0 ;-0002 Start of user memory
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global _DPBp
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global MARK0026H
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; A reference seems to indicate that this should start at offset 26h.
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MARK0026H equ $
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_DPBp dd 0 ; 0000 First drive Parameter Block
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global _sfthead
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_sfthead dd 0 ; 0004 System File Table head
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global _clock
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_clock dd 0 ; 0008 CLOCK$ device
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global _syscon
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_syscon dw _con_dev,seg _con_dev ; 000c console device
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global _maxbksize
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_maxbksize dw 512 ; 0010 maximum bytes/sector of any block device
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dd 0 ; 0012 pointer to buffers info structure
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global _CDSp
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_CDSp dd 0 ; 0016 Current Directory Structure
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global _FCBp
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_FCBp dd 0 ; 001a FCB table pointer
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global _nprotfcb
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_nprotfcb dw 0 ; 001e number of protected fcbs
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global _nblkdev
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_nblkdev db 0 ; 0020 number of block devices
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global _lastdrive
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_lastdrive db 0 ; 0021 value of last drive
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global _nul_dev
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_nul_dev: ; 0022 device chain root
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extern _con_dev:wrt LGROUP
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dw _con_dev, seg _con_dev
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; next is con_dev at init time.
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dw 8004h ; attributes = char device, NUL bit set
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dw _nul_strtgy
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dw _nul_intr
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db 'NUL '
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global _njoined
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_njoined db 0 ; 0034 number of joined devices
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dw 0 ; 0035 DOS 4 pointer to special names (always zero in DOS 5)
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setverPtr dw 0,0 ; 0037 setver list
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dw 0 ; 003B cs offset for fix a20
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dw 0 ; 003D psp of last umb exec
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global _LoL_nbuffers
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_LoL_nbuffers dw 1 ; 003F number of buffers
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dw 1 ; 0041 size of pre-read buffer
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global _BootDrive
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_BootDrive db 1 ; 0043 drive we booted from
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%IFNDEF I386
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db 0 ; 0044 cpu type (1 if >=386)
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%ELSE
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db 1 ; 0044 cpu type (1 if >=386)
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%ENDIF
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dw 0 ; 0045 Extended memory in KBytes
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buf_info:
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global _firstbuf
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_firstbuf dd 0 ; 0047 disk buffer chain
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dw 0 ; 004B Number of dirty buffers
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dd 0 ; 004D pre-read buffer
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dw 0 ; 0051 number of look-ahead buffers
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global _bufloc
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_bufloc db 0 ; 0053 00=conv 01=HMA
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global _deblock_buf
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_deblock_buf dd 0 ; 0054 deblock buffer
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times 3 db 0 ; 0058 unknown
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dw 0 ; 005B unknown
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db 0, 0FFh, 0 ; 005D unknown
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global _VgaSet
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_VgaSet db 0 ; 0060 unknown
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dw 0 ; 0061 unknown
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global _uppermem_link
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_uppermem_link db 0 ; 0063 upper memory link flag
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_min_pars dw 0 ; 0064 minimum paragraphs of memory
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; required by program being EXECed
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global _uppermem_root
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_uppermem_root dw 0ffffh ; 0066 dmd_upper_root (usually 9fff)
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_last_para dw 0 ; 0068 para of last mem search
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SysVarEnd:
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;; FreeDOS specific entries
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global _os_setver_minor
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_os_setver_minor db 0
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global _os_setver_major
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_os_setver_major db 5
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global _os_minor
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_os_minor db 0
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global _os_major
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_os_major db 5
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global _rev_number
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_rev_number db 0
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global _version_flags
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_version_flags db 0
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global _f_nodes
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_f_nodes dw 0
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global _f_nodes_cnt
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_f_nodes_cnt dw 0
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global os_release
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extern _os_release
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os_release dw _os_release
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;; The first 5 sft entries appear to have to be at DS:00cc
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times (0cch - ($ - DATASTART)) db 0
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global _firstsftt
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_firstsftt:
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dd -1 ; link to next
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dw 5 ; count
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; Some references seem to indicate that this data should start at 01fbh in
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; order to maintain 100% MS-DOS compatibility.
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times (01fbh - ($ - DATASTART)) db 0
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global MARK01FBH
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MARK01FBH equ $
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global _local_buffer ; local_buffer is 256 bytes long
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; so it overflows into kb_buf!!
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; only when kb_buf is used, local_buffer is limited to 128 bytes.
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_local_buffer: times 128 db 0
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global _kb_buf
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_kb_buf db 128,0 ; initialise buffer to empty
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times 128+1 db 0 ; room for 128 byte readline + LF
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;
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; Variables that follow are documented as part of the DOS 4.0-6.X swappable
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; data area in Ralf Browns Interrupt List #56
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;
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; this byte is used for ^P support
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global _PrinterEcho
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_PrinterEcho db 0 ;-34 - 0 = no printer echo, ~0 echo
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global _verify_ena
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_verify_ena db 0 ; ~0, write with verify
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; this byte is used for TAB's
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global _scr_pos
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_scr_pos db 0 ; Current Cursor Column
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global _switchar
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_switchar db '/' ;-31 - switch char
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global _mem_access_mode
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_mem_access_mode db 0 ;-30 - memory allocation strategy
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global sharing_flag
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sharing_flag db 0 ; 00 = sharing module not loaded
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; 01 = sharing module loaded, but
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; open/close for block devices
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; disabled
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; FF = sharing module loaded,
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; open/close for block devices
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; enabled (not implemented)
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global _net_set_count
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_net_set_count db 1 ;-28 - count the name below was set
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global _net_name
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_net_name db ' ' ;-27 - 15 Character Network Name
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db 00 ; Terminating 0 byte
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;
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; Variables contained the the "STATE_DATA" segment contain
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; information about the STATE of the current DOS Process. These
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; variables must be preserved regardless of the state of the INDOS
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; flag.
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;
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; All variables that appear in "STATE_DATA" **MUST** be declared
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; in this file as the offsets from the INTERNAL_DATA variable are
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; critical to the DOS applications that modify this data area.
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;
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;
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global _ErrorMode, _InDOS
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global _CritErrLocus, _CritErrCode
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global _CritErrAction, _CritErrClass
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global _CritErrDev, _CritErrDrive
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global _dta
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global _cu_psp, _default_drive
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global _break_ena
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global _return_code
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global _internal_data
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global _CritPatch
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_CritPatch dw 0d0ch ;-11 zero list of patched critical
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dw 0d0ch ; section variables
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dw 0d0ch
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dw 0d0ch
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dw 0d0ch
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db 0 ;-01 - unknown
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_internal_data: ; <-- Address returned by INT21/5D06
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_ErrorMode db 0 ; 00 - Critical Error Flag
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_InDOS db 0 ; 01 - Indos Flag
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_CritErrDrive db 0 ; 02 - Drive on write protect error
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_CritErrLocus db 0 ; 03 - Error Locus
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_CritErrCode dw 0 ; 04 - DOS format error Code
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_CritErrAction db 0 ; 06 - Error Action Code
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_CritErrClass db 0 ; 07 - Error Class
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_CritErrDev dd 0 ; 08 - Failing Device Address
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_dta dd 0 ; 0C - current DTA
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_cu_psp dw 0 ; 10 - Current PSP
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break_sp dw 0 ; 12 - used in int 23
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_return_code dw 0 ; 14 - return code from process
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_default_drive db 0 ; 16 - Current Drive
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_break_ena db 1 ; 17 - Break Flag (default TRUE)
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db 0 ; 18 - flag, code page switching
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db 0 ; 19 - flag, copy of 18 on int 24h abort
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global _swap_always, _swap_indos
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_swap_always:
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global _Int21AX
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_Int21AX dw 0 ; 1A - AX from last Int 21
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global owning_psp, _MachineId
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owning_psp dw 0 ; 1C - owning psp
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_MachineId dw 0 ; 1E - remote machine ID
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dw 0 ; 20 - First usable mcb
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dw 0 ; 22 - Best usable mcb
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dw 0 ; 24 - Last usable mcb
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dw 0 ; 26 - memory size in paragraphs
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dw 0 ; 28 - unknown
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db 0 ; 2A - unknown
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db 0 ; 2B - unknown
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db 0 ; 2C - unknown
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global _break_flg
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_break_flg db 0 ; 2D - Program aborted by ^C
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db 0 ; 2E - unknown
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db 0 ; 2F - not referenced
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global _DayOfMonth
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_DayOfMonth db 1 ; 30 - day of month
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global _Month
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_Month db 1 ; 31 - month
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global _YearsSince1980
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_YearsSince1980 dw 0 ; 32 - year since 1980
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daysSince1980 dw 0FFFFh ; 34 - number of days since epoch
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; force rebuild on first clock read
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global _DayOfWeek
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_DayOfWeek db 2 ; 36 - day of week
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_console_swap db 0 ; 37 console swapped during read from dev
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global _dosidle_flag
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_dosidle_flag db 1 ; 38 - safe to call int28 if nonzero
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_abort_progress db 0 ; 39 - abort in progress
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global _CharReqHdr
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_CharReqHdr:
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global _ClkReqHdr
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_ClkReqHdr times 30 db 0 ; 3A - Device driver request header
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dd 0 ; 58 - pointer to driver entry
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global _MediaReqHdr
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_MediaReqHdr times 22 db 0 ; 5C - Device driver request header
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global _IoReqHdr
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_IoReqHdr times 30 db 0 ; 72 - Device driver request header
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times 6 db 0 ; 90 - unknown
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global _ClkRecord
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_ClkRecord times 6 db 0 ; 96 - CLOCK$ transfer record
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dw 0 ; 9C - unknown
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global __PriPathBuffer
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__PriPathBuffer times 80h db 0 ; 9E - buffer for file name
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global __SecPathBuffer
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__SecPathBuffer times 80h db 0 ;11E - buffer for file name
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global _sda_tmp_dm
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_sda_tmp_dm times 21 db 0 ;19E - 21 byte srch state
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global _SearchDir
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_SearchDir times 32 db 0 ;1B3 - 32 byte dir entry
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global _TempCDS
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_TempCDS times 88 db 0 ;1D3 - TemporaryCDS buffer
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global _DirEntBuffer
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_DirEntBuffer times 32 db 0 ;22B - space enough for 1 dir entry
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global _wAttr
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_wAttr dw 0 ;24B - extended FCB file attribute
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global _SAttr
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_SAttr db 0 ;24D - Attribute Mask for Dir Search
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global _OpenMode
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_OpenMode db 0 ;24E - File Open Attribute
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times 3 db 0
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global _Server_Call
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_Server_Call db 0 ;252 - Server call Func 5D sub 0
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db 0
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; Pad to 05CCh
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times (25ch - ($ - _internal_data)) db 0
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global _tsr ; used by break and critical error
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_tsr db 0 ;25C - handlers during termination
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db 0 ;25D - padding
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global term_psp
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term_psp dw 0 ;25E - 0??
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global int24_esbp
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int24_esbp times 2 dw 0 ;260 - pointer to criticalerr DPB
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global _user_r, int21regs_off, int21regs_seg
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_user_r:
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int21regs_off dw 0 ;264 - pointer to int21h stack frame
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int21regs_seg dw 0
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global critical_sp
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critical_sp dw 0 ;268 - critical error internal stack
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global current_ddsc
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current_ddsc times 2 dw 0
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; Pad to 059ah
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times (27ah - ($ - _internal_data)) db 0
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global current_device
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current_device times 2 dw 0 ;27A - 0??
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global _lpCurSft
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_lpCurSft times 2 dw 0 ;27e - Current SFT
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global _current_ldt
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_current_ldt times 2 dw 0 ;282 - Current CDS
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global _sda_lpFcb
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_sda_lpFcb times 2 dw 0 ;286 - pointer to callers FCB
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global _current_sft_idx
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_current_sft_idx dw 0 ;28A - SFT index for next open
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; used by MS NET
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; Pad to 05b2h
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times (292h - ($ - _internal_data)) db 0
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dw __PriPathBuffer ; 292 - "sda_WFP_START" offset in DOS DS of first filename argument
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dw __SecPathBuffer ; 294 - "sda_REN_WFP" offset in DOS DS of second filename argument
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; Pad to 05ceh
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times (2aeh - ($ - _internal_data)) db 0
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global _current_filepos
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_current_filepos times 2 dw 0 ;2AE - current offset in file
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; Pad to 05f0h
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times (2d0h - ($ - _internal_data)) db 0
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global _prev_user_r
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global prev_int21regs_off
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global prev_int21regs_seg
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_prev_user_r:
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prev_int21regs_off dw 0 ;2D0 - pointer to prev int 21 frame
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prev_int21regs_seg dw 0
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; Pad to 05fdh
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times (2ddh - ($ - _internal_data)) db 0
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global _ext_open_action
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global _ext_open_attrib
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global _ext_open_mode
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_ext_open_action dw 0 ;2DD - extended open action
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_ext_open_attrib dw 0 ;2DF - extended open attrib
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_ext_open_mode dw 0 ;2E1 - extended open mode
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; Pad to 0620h
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times (300h - ($ - _internal_data)) db 0
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global _szNames
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_szNames:
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;; times 11 db 0
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global _FcbSearchBuffer ; during FCB search 1st/next use bottom
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_FcbSearchBuffer: ; of error stack as scratch buffer
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; times 43 db 0 ; - only used during int 21 call
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; stacks are made to initialize to no-ops so that high-water
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; testing can be performed
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global apistk_bottom
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apistk_bottom:
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times STACK_SIZE dw 0x9090 ;300 - Error Processing Stack
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global _error_tos
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_error_tos:
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times STACK_SIZE dw 0x9090 ;480 - Disk Function Stack
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global _disk_api_tos
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_disk_api_tos:
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times STACK_SIZE dw 0x9090 ;600 - Char Function Stack
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global _char_api_tos
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_char_api_tos:
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apistk_top:
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db 0 ; 780 ???
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_VolChange db 0 ;781 - volume change
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_VirtOpen db 0 ;782 - virtual open flag
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; controlled variables end at offset 78Ch so pad to end
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times (78ch - ($ - _internal_data)) db 0
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;
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; end of controlled variables
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;
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segment _BSS
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;!! global _NumFloppies
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;!!_NumFloppies resw 1
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;!!intr_dos_stk resw 1
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;!!intr_dos_seg resw 1
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; mark front and end of bss area to clear
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segment IB_B
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global __ib_start
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__ib_start:
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segment IB_E
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global __ib_end
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__ib_end:
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;; do not clear the other init BSS variables + STACK: too late.
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; kernel startup stack
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global init_tos
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resw 512
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init_tos:
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; the last paragraph of conventional memory might become an MCB
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resb 16
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global __init_end
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__init_end:
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init_end:
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segment _DATA
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; blockdev private stack
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global blk_stk_top
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times 192 dw 0
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blk_stk_top:
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; clockdev private stack
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global clk_stk_top
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times 64 dw 0
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clk_stk_top:
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; Dynamic data:
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; member of the DOS DATA GROUP
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; and marks definitive end of all used data in kernel data segment
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;
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segment _DATAEND
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_swap_indos:
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; we don't know precisely what needs to be swapped before this, so set it here.
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; this is just after FIXED_DATA+BSS+DATA and before (D)CONST+BSS
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; probably, the clock and block stacks and disktransferbuffer should go past
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; _swap_indos but only if int2a ah=80/81 (critical section start/end)
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; are called upon entry and exit of the device drivers
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segment DYN_DATA
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global _Dyn
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_Dyn:
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DynAllocated dw 0
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segment ID_B
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global __INIT_DATA_START
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__INIT_DATA_START:
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segment ID_E
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global __INIT_DATA_END
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__INIT_DATA_END:
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segment INIT_TEXT_START
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global __InitTextStart
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__InitTextStart: ; and c version
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;
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; start end end of HMA area
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segment HMA_TEXT_START
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global __HMATextAvailable
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__HMATextAvailable
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global __HMATextStart
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__HMATextStart:
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;
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; the HMA area is filled with 1eh+3(=sizeof VDISK) = 33 byte dummy data,
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; so nothing will ever be below 0xffff:0031
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;
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segment HMA_TEXT
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begin_hma:
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times 10h db 0 ; filler [ffff:0..ffff:10]
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times 20h db 0
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db 0
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; to minimize relocations
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global _DGROUP_
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_DGROUP_ dw DGROUP
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%ifdef WATCOM
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; 32 bit multiplication + division
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global __U4M
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__U4M:
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LMULU
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global __U4D
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__U4D:
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LDIVMODU
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%endif
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resb 0xd0 - ($-begin_hma)
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; reserve space for far jump to cp/m routine
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resb 5
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;End of HMA segment
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segment HMA_TEXT_END
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global __HMATextEnd
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__HMATextEnd: ; and c version
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|
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; The default stack (_TEXT:0) will overwrite the data area, so I create a dummy
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; stack here to ease debugging. -- ror4
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segment _STACK class=STACK stack
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segment CONST
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; dummy interrupt return handlers
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global _int22_handler
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global _int28_handler
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global _int2a_handler
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global _empty_handler
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_int22_handler:
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_int28_handler:
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_int2a_handler:
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_empty_handler:
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iret
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global _initforceEnableA20
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initforceEnableA20:
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|
call near forceEnableA20
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retf
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global __HMARelocationTableStart
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__HMARelocationTableStart:
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|
|
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global _int2f_handler
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extern reloc_call_int2f_handler
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_int2f_handler: jmp 0:reloc_call_int2f_handler
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call near forceEnableA20
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global _int20_handler
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extern reloc_call_int20_handler
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_int20_handler: jmp 0:reloc_call_int20_handler
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call near forceEnableA20
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global _int21_handler
|
|
extern reloc_call_int21_handler
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|
_int21_handler: jmp 0:reloc_call_int21_handler
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call near forceEnableA20
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|
|
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global _low_int25_handler
|
|
extern reloc_call_low_int25_handler
|
|
_low_int25_handler: jmp 0:reloc_call_low_int25_handler
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call near forceEnableA20
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global _low_int26_handler
|
|
extern reloc_call_low_int26_handler
|
|
_low_int26_handler: jmp 0:reloc_call_low_int26_handler
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|
call near forceEnableA20
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|
|
|
global _int27_handler
|
|
extern reloc_call_int27_handler
|
|
_int27_handler: jmp 0:reloc_call_int27_handler
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|
call near forceEnableA20
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global _int0_handler
|
|
extern reloc_call_int0_handler
|
|
_int0_handler: jmp 0:reloc_call_int0_handler
|
|
call near forceEnableA20
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|
|
|
global _int6_handler
|
|
extern reloc_call_int6_handler
|
|
_int6_handler: jmp 0:reloc_call_int6_handler
|
|
call near forceEnableA20
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|
|
|
global _cpm_entry
|
|
extern reloc_call_cpm_entry
|
|
_cpm_entry: jmp 0:reloc_call_cpm_entry
|
|
call near forceEnableA20
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|
|
|
global _reloc_call_blk_driver
|
|
extern _blk_driver
|
|
_reloc_call_blk_driver:
|
|
jmp 0:_blk_driver
|
|
call near forceEnableA20
|
|
|
|
global _reloc_call_clk_driver
|
|
extern _clk_driver
|
|
_reloc_call_clk_driver:
|
|
jmp 0:_clk_driver
|
|
call near forceEnableA20
|
|
|
|
global _CharMapSrvc ; in _DATA (see AARD)
|
|
extern _reloc_call_CharMapSrvc
|
|
_CharMapSrvc: jmp 0:_reloc_call_CharMapSrvc
|
|
call near forceEnableA20
|
|
|
|
|
|
global __HMARelocationTableEnd
|
|
__HMARelocationTableEnd:
|
|
|
|
;
|
|
; if we were lucky, we found all entries from the outside to the kernel.
|
|
; if not, BUMS
|
|
;
|
|
;
|
|
; this routine makes the HMA area available. PERIOD.
|
|
; must conserve ALL registers
|
|
; will be only ever called, if HMA (DOS=HIGH) is enabled.
|
|
; for obvious reasons it should be located at the relocation table
|
|
;
|
|
global _XMSDriverAddress
|
|
_XMSDriverAddress:
|
|
dw 0 ; XMS driver, if detected
|
|
dw 0
|
|
|
|
global __EnableA20
|
|
__EnableA20:
|
|
mov ah,5
|
|
UsingXMSdriver:
|
|
push bx
|
|
call far [cs:_XMSDriverAddress]
|
|
pop bx
|
|
retf
|
|
|
|
global __DisableA20
|
|
__DisableA20:
|
|
mov ah,6
|
|
jmp short UsingXMSdriver
|
|
|
|
dslowmem dw 0
|
|
eshighmem dw 0ffffh
|
|
|
|
global forceEnableA20
|
|
forceEnableA20:
|
|
|
|
push ds
|
|
push es
|
|
push ax
|
|
|
|
forceEnableA20retry:
|
|
mov ds, [cs:dslowmem]
|
|
mov es, [cs:eshighmem]
|
|
|
|
mov ax, [ds:00000h]
|
|
cmp ax, [es:00010h]
|
|
jne forceEnableA20success
|
|
|
|
mov ax, [ds:00002h]
|
|
cmp ax, [es:00012h]
|
|
jne forceEnableA20success
|
|
|
|
mov ax, [ds:00004h]
|
|
cmp ax, [es:00014h]
|
|
jne forceEnableA20success
|
|
|
|
mov ax, [ds:00006h]
|
|
cmp ax, [es:00016h]
|
|
jne forceEnableA20success
|
|
|
|
;
|
|
; ok, we have to enable A20 )at least seems so
|
|
;
|
|
|
|
call far __EnableA20
|
|
|
|
jmp short forceEnableA20retry
|
|
|
|
|
|
|
|
forceEnableA20success:
|
|
pop ax
|
|
pop es
|
|
pop ds
|
|
ret
|
|
|
|
;
|
|
; global f*cking compatibility issues:
|
|
;
|
|
; very old brain dead software (PKLITE, copyright 1990)
|
|
; forces us to execute with A20 disabled
|
|
;
|
|
|
|
global _ExecUserDisableA20
|
|
|
|
_ExecUserDisableA20:
|
|
|
|
cmp word [cs:_XMSDriverAddress],0
|
|
jne NeedToDisable
|
|
cmp word [cs:_XMSDriverAddress+2],0
|
|
je noNeedToDisable
|
|
NeedToDisable:
|
|
push ax
|
|
call far __DisableA20
|
|
pop ax
|
|
noNeedToDisable:
|
|
iret
|
|
|
|
|
|
;
|
|
; Default Int 24h handler -- always returns fail
|
|
; so we have not to relocate it (now)
|
|
;
|
|
FAIL equ 03h
|
|
|
|
global _int24_handler
|
|
_int24_handler: mov al,FAIL
|
|
iret
|
|
|
|
;
|
|
; this makes some things easier
|
|
;
|
|
|
|
segment _LOWTEXT
|
|
global _TEXT_DGROUP
|
|
_TEXT_DGROUP dw DGROUP
|
|
|
|
segment INIT_TEXT
|
|
global _INIT_DGROUP
|
|
_INIT_DGROUP dw DGROUP
|