TSR for virtual INT 13h disk in high memory (under development.)

1 files changed, 167 insertions, 0 deletions

diff --git a/memdisk/memdisk.asm b/memdisk/memdisk.asm
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+++ b/memdisk/memdisk.asm
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+; -*- fundamental -*- (asm-mode sucks)
+; $Id$
+; ****************************************************************************
+;
+;  memdisk.asm
+;
+;  A program to emulate an INT 13h disk BIOS from a "disk" in extended
+;  memory.
+;
+;   Copyright (C) 2001  H. Peter Anvin
+;
+;  This program is free software; you can redistribute it and/or modify
+;  it under the terms of the GNU General Public License as published by
+;  the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
+;  USA; either version 2 of the License, or (at your option) any later
+;  version; incorporated herein by reference.
+; 
+; ****************************************************************************
+
+		org 0h
+
+MyStack		equ 1024
+
+		; Parameter registers definition; this is the definition
+		; of the stack frame.
+%define		P_EAX		dword [bp+28]
+%define		P_AX		word [bp+28]
+%define		P_AL		byte [bp+28]
+%define		P_AH		byte [bp+29]
+%define		P_ECX		dword [bp+24]
+%define		P_CX		word [bp+24]
+%define		P_CL		byte [bp+24]
+%define		P_CH		byte [bp+25]
+%define		P_EDX		dword [bp+20]
+%define		P_DX		word [bp+20]
+%define		P_DL		byte [bp+20]
+%define		P_DH		byte [bp+21]
+%define		P_EBX		dword [bp+16]
+%define		P_BX		word [bp+16]
+%define		P_BL		byte [bp+16]
+%define		P_BH		byte [bp+17]
+%define		P_EBP		dword [bp+8]
+%define		P_BP		word [bp+8]
+%define		P_ESI		dword [bp+4]
+%define		P_SI		word [bp+4]
+%define		P_EDI		dword [bp]
+%define		P_DI		word [bp]
+
+		section .text
+Int13Start:
+		; See if DL points to our class of device (FD, HD)
+		push dx
+		xor dl,[cs:DriveNo]
+		pop dx
+		js .nomatch		; If SF=0, we have a match here
+		cmp dl,[cs:DriveNo]
+		je .our_drive
+		jb .nomatch		; Drive < Our drive
+		dec dl			; Drive > Our drive, adjust drive #
+.nomatch:
+		jmp far [OldInt13]
+
+.our_drive:
+		mov [cs:Stack],sp
+		mov [cs:SavedAX],ax
+		mov ax,ss
+		mov [cs:Stack+2],ax
+		mov ax,cs
+		mov ss,ax
+		mov sp,MyStack
+		push ds
+		push es
+		mov ds,ax
+		mov es,ax
+		mov ax,[SavedAX]
+		pushad
+		mov bp,sp
+		cmp ah,Int13FuncsMax
+		jae Invalid
+		xor al,al		; AL = 0 is standard entry condition
+		mov di,ax
+		shr di,7
+		call [Int13Funcs+di]
+
+Done:		; Standard routine for return
+		mov [LastStatus],ah
+		mov P_AX,ax
+		cmp ah,1
+		setnb al		; AL <- (AH > 0) ? 1 : 0 (CF)
+		lds bx,[Stack]		; DS:BX <- Old stack pointer
+		mov [bx+4],al		; Low byte of old FLAGS -> arithmetric flags
+		popad
+		pop es
+		pop ds
+		lss sp,[cs:Stack]
+		iret
+
+Reset:
+		; Reset affects multiple drives, so we need to pass it on
+		pop ax			; Drop return address
+		mov [LastStatus], byte 0
+		popad
+		pop es
+		pop ds
+		lss sp,[cs:Stack]
+		and dl,80h		; Clear all but the type bit
+		jmp far [OldInt13]
+
+GetStatus:
+		mov ah,[LastStatus]	; Copy last status
+		ret
+
+CheckIfReady:
+Recalibrate:
+		xor ah,ah		; Always successful
+		ret
+
+Read:
+Write:
+Verify:
+Format:
+GetParms:
+InitWithParms:
+Seek:
+GetDriveType:
+DetectChange:
+
+Invalid:
+		mov ah,01h		; Unsupported function
+		ret
+
+		section .data
+Int13Funcs	dw Reset		; 00h - RESET
+		dw GetStatus		; 01h - GET STATUS
+		dw Read			; 02h - READ
+		dw Write		; 03h - WRITE
+		dw Verify		; 04h - VERIFY
+		dw Format		; 05h - FORMAT TRACK
+		dw Format		; 06h - FORMAT TRACK AND SET BAD FLAGS
+		dw Format		; 07h - FORMAT DRIVE AT TRACK
+		dw GetParms		; 08h - GET PARAMETERS
+		dw InitWithParms	; 09h - INITIALIZE CONTROLLER WITH DRIVE PARAMETERS
+		dw Invalid		; 0Ah
+		dw Invalid		; 0Bh
+		dw Seek			; 0Ch - SEEK TO CYLINDER
+		dw Reset		; 0Dh - RESET HARD DISKS
+		dw Invalid		; 0Eh
+		dw Invalid		; 0Fh
+		dw CheckIfReady		; 10h - CHECK IF READY
+		dw Recalibrate		; 11h - RECALIBRATE
+		dw Invalid		; 12h
+		dw Invalid		; 13h
+		dw Invalid		; 14h
+		dw GetDriveType		; 15h - GET DRIVE TYPE
+		dw DetectChange		; 16h - DETECT DRIVE CHANGE
+Int13FuncsEnd	equ $
+Int13FuncsMax	equ (Int13FuncsEnd-Int13Funcs) >> 1
+
+DriveNo		db 0			; Our drive number
+LastStatus	db 0			; Last return status
+
+		section .bss
+OldInt13	resd 1			; INT 13h in chain
+Stack		resd 1			; Saved SS:SP on invocation
+SavedAX		resw 1			; AX saved during initialization
+
+