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Assembly Source File | 1987-11-13 | 36.4 KB | 758 lines

; Title MOVBASIC 3-3-86 [9-17-86] [11-13-87 (Yes, FRIDAY the 13TH)] Page 80,132 ;****************************************************************************** ; This is version 5.0 of MOVBASV4.ARC that was circulating on the BBSs ;****************************************************************************** ; by JP (Orlando Fl) ;------------------------------------------------------------------------------ ; Even though the BBS description said it was Version 4 , this programs ; internal messages indicate that it is Version 3.1 ; ; !!!!! THIS VERSION HAS SEVERAL BUG FIXES !!!!! ; ; ; 1). THIS VERSION TRULY SUPPORTS A 80x86 PROCESSORS ; ; as written (and a truly innovative and inspired work!!) ; the program uses "self modifying code". On a PC or 8086/88 ; the program would work because the 808x has a hardware ; 4 byte intruction pre-fetch buffer. ; ; HOWEVER.. the 80x86 based cpus have a larger prefetch ; queue, 6-8 bytes (depending on 80x86). When you have ; an instruction modifying code immediately after the ; modifying instruction, THIS WILL NOT WORK, because the ; the next instruction is not in memory but in the pre-fetch ; queue (SEE!).. The FIX is a few NOPS so that the instructions ; to be modified are STILL in memory and CAN be modified. ; ; ; ** THE RULE : DON'T WRITE SELF-MODIFYING CODE ** ; ; 2). This modified version INCREASES the stack so you can trace ; the startup IPL code. The stack in version 3.1 was 1 byte ; above the startup code and since the stack writes down in ; memory, a trace would overwrite startup code before you got ; going good. ; 3). ALSO, code was added to initialize the program work areas ; to zeros. If you did not , then each time you ran MOVBASIC ; the first few bytes of each SBASICx would be garbage and ; would not cause an equal compare to a previous SBASICx. ; 4). The calculation of the NEGATIVE CHECKSUM for the .EXE ; IS NOT necessary , DOS does NOT use it at all to to ; verify the validity of the .EXE module. I believe it ; is being calculated incorrectly anyway, SO NO LOSE. ; ;****************************************************************************** ;This program must be run on an IBM-PC or IBM-PC/AT or PS/2 with ROMS installed ;****************************************************************************** ; ; ** BASIC.COM and BASICA.COM must reside in same directory as MOVBASIC. ** ; ; The program takes IBM BASIC.COM or BASICA.COM and combines it with the ; ROM image to create a new file called SBASIC.COM or SBASICA.COM, and ; it now works with files above 32k such as PC-DOS 3.2/3.3 file, BASICA.COM ; ; Also note, that for IBM version 3.3 there is no longer a BASIC.COM. ; There is only a BASICA.COM. The stub program BASIC.COM just loads ; BASICA.COM instead. ; ; So , for IBM PC DOS 3.3 DONT run MOVBASIC against BASIC.COM ; ----------------------------------------------------------- ; ; These new programs can be run on clones with out the copyrighted IBM ; --------------------------------------------------------------------- ; basic ROMS, and will act as if they were running on a true IBM-PC ; ------------------------------------------------------------------- ; ; Works great, type MOVBASIC and follow the prompts... ; ; To generate the executable MOVBASIC.COM file, please type ; ; MASM MOVBASIC; ; LINK MOVBASIC; ; EXE2BIN MOVBASIC.EXE MOVBASIC.COM ; DEL MOVBASIC.EXE ; DEL MOVBASIC.OBJ ; ; ; Since "EXE2BIN" is no longer included with DOS 3.3 use the ; "public domain" version on BBSs called : "EXE2COM". It is included ; with this ARC version of MOVBASIC version 5.0. ; ; lf equ 0Ah ; Ascii carriage return cr equ 0Dh ; Ascii line feed ; fcb equ 5Ch ; Address of FCB in PSP fixmax equ 50h ; Maximum number of fixups ; ; prog segment assume cs:prog ,ds:prog, es:prog ,ss:prog org 0100h start: jmp main ; ; ;***************************************************************************** ; MODIFIED : 11-13-87 by JP (Orlando Fl) ; ; Moved all data to start of program (for my own reasons.) ; ;***************************************************************************** rommsg db cr,lf db 'Please run this program on an IBM computer with' db ' the basic ROMS installed',cr,lf,7,'$' tries db 2 ; Attempts before we give up ; banner db cr,lf,lf db ' BASIC Relocation Utility Version 5.00' db cr,lf,lf, db ' [11-13-87]' db cr,lf, db ' Friday the 13th' db cr,lf, db ' JP (Orlando fl)' db cr,lf,lf, db 'This program will convert BASIC.COM or BASICA.COM into' db ' SBASIC[A].COM which is',cr,lf db 'usable on CLONE COMPUTERs that do not have IBM`s patented ' db 'BASIC ROMs installed',cr,lf,lf db 'If you have BASIC[A].COM on non-default drive',2Ch db 'then specify that in the command ',cr,lf db 'line. For ex. MOVBASIC A:BASIC B: will create SBASIC.' db 'COM on the B: drive. ',cr,lf,lf db 'Select BASIC to patch for CLONE (non-IBM) computer' db cr,lf,lf db ' 1. BASIC.COM --> SBASIC.COM',cr,lf db ' 2. BASICA.COM --> SBASICA.COM',cr,lf db ' --> $' ; filmsg db cr,lf,'Cannot find specified file. Please retry.',7,'$' ; ifile db 0 ; Disk number db 'BASIC' ; ...filename ifpat db ' ' ; ...possibly 'A' db 'COM' ; ...extension ; ; *** Start of real FCB structure for output file ; ofile db 0 ; Disk number db 'SBASIC' ; ...filename ofpat db ' ' ; ...possibly 'A' db ' COM' ; ...extension dw 0 ; Current record in FCB orecl dw 0 ; Output record size db 11h dup(0) ; ...rest of FCB orecn dw 0,0 ; Output record number ; ; *** End of real FCB structure for output file ; bigmsg db cr,lf db 'Your BASIC file is too big',cr,lf,7,'$' commsg db cr,lf db 'Not COM file',cr,lf,7,'$' cremsg db cr,lf db 'Can',27h,'t create SBASIC',cr,lf,7,'$' dskmsg db cr,lf db 'Output disk full',cr,lf,7,'$' fulmsg db cr,lf db 'Too many fixups',cr,lf,7,'$' ; ; Main proc near ;Main procedure ; ; MODIFIED 11-13-87 : turn interrupts off during stack switch (to be safe) ; cli mov sp,offset start ; ..use local stack sti ; ; MODIFIED 11-13-87 : following call added to clear progarm memory ; call clear ; ..clear rest of our segment call copy ; ..read ROM call rfile ; ..read BASICx.COM call fixup ; ..scan BASICx.COM for Fixups call sizit ; ..find size, save in HDR ; ; MODIFIED 11-13-87 :the call to chksum was commented out (not necessary) ; call chksum ; ..save chksum in HDR call wfile ; ..write Fixups+ROM+BASICx.COM int 20h ; ..all done, back to DOS main endp ; ..end of main procedure ; ; subttl clear - procedure to clear programs working memory (good housekeeping) clear proc near ; zero the rest of our segment push ax ; save some regs push cx push di cld ; set forward reference xor ax,ax ; figure difference from top mov bx,0ffffh ; of program to end of working mov di,offset fixups ; code AND zero it out sub bx,di repz stosb pop di ; restore regs pop cx pop ax ret clear endp ; ; subttl copy - procedure to make copy of hardware 'ROM' basic copy proc near ; Makes copy of ROM xor ax,ax ; ...get bios data mov ds,ax ; ...area in ds seg mov bx,60h ; ...BX --> basic in 'ROM's mov ax,[bx+0] ; Check ibm ROM vector offset or ax,ax ; ...offset must be zero jnz badrom ; ...else no IBM roms mov ax,[bx+2] ; Check ibm ROM vector segment cmp ax,0F600h ; ...must begin at F600 jnz badrom ; ...else no IBM roms mov ds,ax ; AX --> IBM rom segment mov cx,8000h ; CX == size of ROM basic mov di,offset ibmbas ; DI --> Private 'ROM' offset mov si,0 ; SI --> IBM 'ROM' offset cld ; ...direction forwards repz movsb ; Copy IBM rom into 'ROM' area push cs ; ...then restore pop ds ; ...data segment ret ; All done, back to caller ; badrom: push cs ; Restore the pop ds ; ...data segment mov dx,offset rommsg ; DX --> error message jmp near ptr errxit ; ...print and expire copy endp ; End of copy procedure ; ; ; subttl rfile - procedure to read contents of original ibm BASICx.COM file rfile proc near ; Procedure reads BASICx.COM mov al,byte ptr ds:fcb+01h ; AL = First char of filename cmp al,20h ;' ' ; ...was filename specified jz menu ; ...no, then prompt for it mov al,byte ptr ds:fcb+10h ; Was a disk number specified? cmp al,0Fh ; ...valid only up to 0Fh jb disk ; Else force default disk xor al,al ; ...by zeroing disk number ; disk: mov ofile,al ; Save disk number in FCB jmp short try ; ...try to open file ; menu: call prompt ; Print selection for user try: mov di,offset fcb+09h ; DI --> extension in FCB mov ax,04F43h ; AX == 'CO' cld ; ...clear direction stosw ; ...save 'CO' in extension mov al,4Dh ;'M' ; AL == 'M' stosb ; ...save 'M' in extension mov cx,1Eh ; CX == byte count for reset xor al,al ; AL == what to put in bytes repz stosb ; ...reset remainder of FCB mov ah,0Fh ; AH == open existing file mov dx,offset fcb ; DX --> fcb for this file int 21h ; ...try to open the file or al,al ;Test the return code from DOS jz opened ; ...all is ok mov dx,offset filmsg ; Else DX --> nasty message mov ah,09h ; ... AX == DOS print request int 21h ; ... let DOS complain dec byte ptr tries ; One less retry (began with 2) jnz menu ; ... has second chance int 20h ; Else call the terminator ; opened: mov word ptr ds:fcb+0Eh,01h ; Records are 1h bytes long push ds ; Save data segment mov ah,1Ah ; AH == set disk xfer address mov bx,ds ; Get current segment add bx,800h ; ...point beyond ROMs mov ds,bx ; Load into DS segment mov dx,offset ibmbas ; ...xfer address = 'ROM'end int 21h ; ...tell DOS to set address pop ds ; Restore data segment mov ah,27h ; Attempt to read entire file mov cx,offset 0FFFFh ; ...only up to 64k bytes mov dx,offset fcb ; ...with this FCB int 21h ; ...into disk xfer address cmp al,01h ; Must return end_of_file jnz huge ; ...else file is oversize cmp ds:ibmbas+8000h,5A4Dh ; Is file a COM file? je exefil ; ...no, can't move it mov word ptr ds:ifsize,cx ; Save size in 1h byte blocks ret ; ...all done read, return ; huge: jmp near ptr toobig ; ...else can't convert exefil: jmp near ptr notcom ; ...not a COM file rfile endp ; End of read file procedure ; ; subttl prompt - procedure to get filename from user prompt proc near ; Prompt for BASICx file name mov dx,offset banner ; DX --> display mov ah,09h ; AH == print string int 21h ; ...ask DOS to print prompt mov ah,01h ; Read reply from console int 21h ; ...this DOS request sub al,31h ; Was it choice #1? jz newnam ; ...yup cmp al,01h ; Was it choice #2? jnz prompt ; ...nope, must be 1 or 2 mov byte ptr ifpat,41h ;'A' ; Add 'A' to end of filename ; newnam: mov si,offset ifile ; Pack explicit name mov di,offset fcb ; ...into input FCB mov cx,0Ch ; ...length of name cld ; Clear direction flag repz movsb ; ...copy name there mov cx,18h ; ...reset input FCB xor al,al ; ...write zero to it repz stosb ; ...with instruction ret ; Back to caller prompt endp ; ...end of procedure ; ; subttl fixup - procedure to build table of fixup offsets fixup proc near ; Revector ROM references mov bx,offset ibmbas ; BX => BASICx.COM in memory mov cx,word ptr ds:ifsize ; CX == Size in 1h byte blocks mov dx,0F600h ; DX == hardware (ROM) address push ds ; Save data segment mov ax,ds ; Get data segment add ax,800h ; ...move beyond ROMs mov ds,ax ; Load into data segment mov di,offset fixups ; DI -> start of fixup table cld ; ...clear direction flag ; fixing: cmp dx,[bx] ; BASICx.COM want ROM segment? jnz next ; ...no, do not alter call lookup ; Should seg. ref. be fixed up? jnz next ; ...flag 'Z' clear if no mov ax,bx ; Get address that needs fixup sub ax,offset ibmbas ; ...find BASICx.COM offset stosw ; Store offset in fixups table inc word ptr cs:nfixes ; ...one more offset in table next: inc bx ; Scan the next byte loop fixing ; ...until done BASICx.COM pop ds ; Restore Data segment cmp word ptr ds:nfixes,fixmax ; Did fixup table overflow? ja loaded ; ...jump if so ret ; Else end of fixup procedure ; loaded: jmp near ptr tooful ; Fixup table overloaded ; fixup endp ; ...show end ; subttl lookup - find if offset into BASICx.COM needs fixup ; ; Lookup - procedure sets 'Z' flag if this F600h reference needs a fixup ; lookup proc near ; See if reference needs fixup cmp byte ptr [bx-3],0EAh jz found cmp byte ptr [bx-1],0B8h jz found cmp byte ptr [bx-1],0BBh jz found cmp byte ptr [bx-1],0BEh jz found cmp byte ptr [bx-1],0BAh jz found cmp byte ptr [bx-1],0BFh jz found cmp byte ptr [bx-1],0B9h jz found cmp byte ptr [bx-3],09Ah jz found cmp word ptr [bx-4],06C7h jz found cmp word ptr [bx-4],87C7h jz found cmp word ptr [bx-4],84C7h jz found cmp word ptr [bx-4],85C7h jz found cmp word ptr [bx-4],86C7h jz found cmp word ptr [bx-3],46C7h jz found cmp word ptr [bx-3],47C7h jz found cmp word ptr [bx-3],44C7h jz found cmp word ptr [bx-3],45C7h jz found cmp word ptr [bx-2],07C7h jz found cmp word ptr [bx-2],04C7h jz found cmp word ptr [bx-2],05C7h found: ret ; Return, result in Z flag lookup endp ; ...end of procedure ; ; subttl sizit - procedure to find size of SBASIC.COM and save in HDR sizit proc near mov ax,offset ibmbas-hdr ; Get header size into AX add ax,8000h ; ...add size of ROM set add ax,word ptr ifsize ; ...and input file size push ax ; Save copy of file size mov cl,09h ; ...find number of blocks rcr ax,cl ; ...by 9 bit right shift and ax,0FFh ; ...0FFh blocks maximum inc ax ; I dunno, but DOS wants it mov word ptr hdr+04h,ax ; Save number of blocks in hdr pop ax ; ...get low order 16 bits and ax,01FFh ; Isolate the block fraction mov word ptr hdr+02h,ax ; ...and save in hdr word ret ; ...return to caller sizit endp ; ; subttl chksum - procedure to calculate and store negative checksum of file chksum proc near xor ax,ax ; Prepare a zero mov dx,word ptr hdr+04h ; Load block count chks01: mov si,offset movrom ; si --> blk start dec dx ; ...show one less js chks03 ; Negative if done mov cx,0100h ; ...words in block chks02: sub ax,[si] ; Subtract word add si,02h ; ...point to next loop chks02 ; ...go until done mov bx,ds ; ...get a copy add bx,0020h ; ...Go to next blk mov ds,bx ; ...and save in ds jmp chks01 ; ...back for next chks03: mov cx,offset hdr+02h ; Get fraction blk shr cx,01h ; ...into words jcxz chks05 ; Zero if all done chks04: sub ax,[si] ; Subtract word add si,02h ; ...point to next loop chks04 ; ...go until done chks05: push cs ; Get code segment pop ds ; ...restore ds mov word ptr hdr+12h,ax ; Negative chksum ret ; ...return caller chksum endp ; ; subttl wfile - procedure to write new SBASICx.COM file wfile proc near ; Procedure writes BASICx.COM mov al,byte ptr ds:fcb+06h ; Last character of filename cmp al,41h ; ...does it end in 'A'? jnz around ; ...no, leave it alone mov ofpat,al ; ...else copy 'A' around: mov ah,16h ; Create output file mov dx,offset ofile ; ...with (patched) FCB int 21h ; ...with system call or al,al ; Did the create work? jnz dskcre ; ...say disk is full mov word ptr orecl,01h ; Records are 1 byte long mov cx,offset ibmbas-hdr ; ...overhead in bytes add cx,8000h ; ...rom size in bytes jc toobig ; Out of memory, complain(?!) mov ah,1Ah ; Set disk transfer address mov dx,offset hdr ; ...to our start-up code int 21h ; ...with this call mov dx,offset ofile ; DX --> Output FCB mov ah,28h ; ...write patched file int 21h ; ...with system call or al,al ; Did the write succeed? jnz dskful ; ...no, say disk is full mov word ptr orecn,cx ; Point to next record push ds ; ...save a copy mov ax,ds ; Get data segment add ax,800h ; ...go beyond roms mov ds,ax ; ...reload new segment mov ah,1Ah ; Set disk transfer address mov dx,offset ibmbas ; ...where to set it to int 21h ; Set disk transfer address pop ds ; ...restore old segment mov ah,28h ; Write unpatched BASICx.COM mov cx,word ptr ifsize ; ...input file (bytes) mov dx,offset ofile ; Write more stuff out int 21h ; ...with this call or al,al ; Did the write succeed? jnz dskful ; ...no, say disk is full mov ah,10h ; Worked, then close file mov dx,offset ofile ; DX --> output FCB int 21h ; Issue the dos call or al,al ; ...did it close? jnz dskful ; No, complain ret ; ...else back to caller ; tooful: mov dx,offset fulmsg ; Fixup table overflowed jmp short errxit ; ...on terminal ; toobig: mov dx,offset bigmsg ;Complain, file is too big jmp short errxit ; ...jump to print message ; notcom: mov dx,offset commsg ;Not a COM file, complain jmp short errxit ; ...jump to print message ; dskcre: mov dx,offset cremsg ;Complain about open error jmp short errxit ; ...jump to print message ; dskful: mov dx,offset dskmsg ;Complain about disk full ; errxit: mov ah,09h ; Function = print message int 21h ; ...ask DOS to type it int 20h ; Then call the terminator wfile endp ; ...end write file procedure ; subttl hdr - everything beyond here added to SBASICx.COM image file ;****************************************************************************** ; ; ; ; ; ; ;****************************************************************************** ; extra equ 27FFh ; Minimum paragraphs to run ; hdr label byte ; Header for SBASICs.COM db 4Dh,5Ah ; ...image .EXE type dw ? ; Fraction of block dw ? ; Blocks in image dw 0h ; Number of relocations dw (0Fh+base-hdr)/10h ; Header size in paragraphs dw (0Fh+fixups-ipl)/10h+extra ; Minimum paragraphs to run dw 0FFFFh ; Maximum paragraphs to run dw 0h ; Offset for SS register dw tos-base ; ...value SP register ; ; MODIFIED 11-13-87 : initialized negative checksum to zeros ; dw 0h ; Negative checksum dw 0h ; Offset for IP register dw 0h ; ...value CS register dw ? ; Byte disp of reloc. list dw 0 ; ...not an overlay ; dw 2 dup(?) ; Align on paragraph boundary ; ; subttl img - everything beyond here will appear in memory when image is loaded ;****************************************************************************** ; ; Everything below this line will appear in the output SBASICx.COM image, and ; will appear in memory when this image is loaded. Memory offsets as follows ; ; ; MODIFIED 11-13-87 : the following address may/will no longer be correct ; as MOVBASIC restructured, to MY my.. JP. ; ; 0000h == Start of PSP (Program Segment Prefix - not part of image ) ;base: 0100h == Symbol GO (Setup COM environment in CS,DS and go there) ; 0111h == Symbol MOVROM (check memory, copy basic ROM to high memory) ; 0139h == Symbol RUNFIX (apply fixups to original BASICx.COM image ) ; 0152h == Symbol MOVIPL (moves IPL code to stack area for execution ) ; 0169h == Symbol IPL (moves ibm BASICx.COM to 0100h and starts it) ; 0192h == Symbol FIXUPS (list of offsets into BASICx.COM for fixups ) ; 0232h == Symbol IBMBAS (copy of ibm basic ROM set, without patches) ; 8232h == (original ibm BASICx.COM without fixups done) ;end: ????h == (end BASICx.COM May not exceed 96k in total) ; ;***************************************************************************** base label byte ; At run-time appears at 0100h ; go proc far ; Setup regs like COM file cli ; No interrupts for now !!! mov ax,cs ; ...get code segment sub ax,10h ; ...then point to PSP mov ds,ax ; ...load into Data Segment mov ds:(100h+goseg-base),ax ; ...save copy for CS ; ; MODIFIED 11-13-87 : nops added to keep code to be modified in memory ; db 8d DUP(90H) ; keeps following code in memory db 0EAh ; Jump far gooff dw 100h+movrom-base ; ...offset for IP goseg dw ? ; ...segment for CS go endp ; ; MODIFIED 11-13-87 : stack space increased to allow traceing of startup code ; EVEN ; force to even address boundry dw 20h dup(0) ; Bootstrap 32 words for stack tos label word ; Procedure GO becomes stack ; ; movrom proc near ; Routine relocates ROM up hi sti mov si,offset ibmbas+100h-base ; SI -> where 'ROM's live now mov di,0 ; DI -> where 'ROM's will be mov ax,cs ; Get our code segment add ax,extra-8FFh ; + minimum memory required xor al,al ; ...round down to even 4K push ax ; Run-time segment for ROM set mov es,ax ; ...load into es for movsb mov cx,8000h ; Bytes in basic 'ROM' set cld ; ...clear the direction repz movsb ; Move ROMs from BASIC data area mov di,si ; DI -> where BASICx.COM is now xor ax,ax ; Prepare es segment to mov es,ax ; ...access vector area mov bx,60h ; BX --> Basic vector into ROM pop dx ; DX --> run-time 'ROM' segment mov es:[bx+2],dx ; ...save 'ROM' seg. in vector mov es:[bx+0],ax ; ...the 'ROM' offset is zero movrom endp ; End of copy_rom procedure ; ; runfix proc near ; Routine does runtime fixups mov cx,0000h ; CX == number of fixups nfixes =$ - 02h ; ...self-modifying code, ugh! mov si,offset fixups+100h-base ; SI -> fixup table mov ax,ds ; Get data segment add ax,800h ; ...go beyond ROMs mov es,ax ; ...and save it sub di,8000h ; do this to avoid fixer: lodsw ; AX == offset into BASICx.COM mov bx,ax ; copy offset into BX mov es:[bx+di],dx ; Fixup ROM ref. in BASICx.COM loop fixer ; ..loop until all fixups done runfix endp ; End of run-time fixup routine ; ; movipl proc far ; Move IPL code to scratch area mov ax,cs ; Get code segment add ax,offset extra-9FFh ; ...find scratch area xor al,al ; ...even boundary push ax ; Save scratch segment pop es ; ...load into ES reg. push ax ; Save scratch segment mov di,0h ; DI -> where IPL code will run push di ; Save offset to IPL code mov si,offset ipl+100h-base ; SI -> where IPL code is now mov cx,offset fixups-ipl ; CX == size of IPL code, bytes repz movsb ; ...copy IPL code to ipl area ret ; ...start final IPL sequence movipl endp ; End of IPL relocate procedure ; ; ipl proc far ; IPL code runs in high memory mov cx,0000h ; CX == size of BASICx.COM file ifsize =$ - 02h ; ...self-modifying code, ugh! mov ax,ds ; Save code segment copy mov es,ax ; ...load into extra seg mov word ptr cs:(iplseg-ipl),ax ; Save code segment for ipl add ax,800h ; ...skip over 32K roms mov ds,ax ; DS register --> ROM now mov si,offset ibmbas+100h-base ; SI -> area BASICx.COM is now mov di,100h ; DI -> area BASICx.COM must go repz movsb ; Copy BASICx.COM to low memory mov ax,es ; Restore data segment mov ds,ax ; ...equal to extra seg mov ss,ax ; Set stack seg for COM mov sp,0FFFEh ; ...stack reg for COM sti ; ...interrupts now safe db 0EAh ; JMP FAR segment:offset iploff dw 100h ; ...offset for COM file iplseg dw ? ; ...Start seg COM file ipl endp ; ..end of IPL procedure ; ; fixups label word ; Fixups as offset in BASIC.COM ibmbas equ fixups + (2 * fixmax) ; Contents of 'ROM's saved here prog ends ; end start