title XMSDISK XMS-aware RAMdisk page 55,132 ; XMSDISK.ASM --- XMS-aware RAMdisk device driver ; Copyright (C) 1989 Ziff Davis Communications ; PC Magazine * Ray Duncan ; Also requires ITOA.ASM and ATOI.ASM. ; ; To build: MASM XMSDISK; ; MASM ATOI; ; MASM ITOA; ; LINK XMSDISK+ATOI+ITOA; ; EXE2BIN XMSDISK.EXE XMSDISK.BIN ; DEL XMSDISK.EXE ; ; To install: copy XMSDISK.SYS to the boot disk, add ; ; DEVICE=XMSDISK.BIN nnnK ; ; to the CONFIG.SYS file. This must follow ; the DEVICE= line that loads the XMM (usually ; HIMEM.SYS). The parameter nnn is the desired ; RAMdisk size in KB. If nnn is missing or zero, ; all available extended memory is used. ; _TEXT segment public 'CODE' extrn atoi:near extrn itoa:near assume cs:_TEXT,ds:_TEXT,es:NOTHING org 0 maxcmd equ 24 ; maximum driver command code cr equ 0dh ; ASCII carriage return lf equ 0ah ; ASCII line feed blank equ 020h ; ASCII space code eom equ '$' ; end of message indicator secsize equ 512 ; bytes per sector (IBM standard) dirsize equ 256 ; entries in root directory request struc ; request packet template len db ? ; length of request packet unit db ? ; unit number for this request command db ? ; request packet's command code status dw ? ; status returned by driver db 8 dup (?) ; reserved area media db ? ; media descriptor byte address dd ? ; memory address for transfer count dw ? ; byte/sector count value sector dw ? ; starting sector value request ends ; end of request packet template header equ $ ; device driver header dd -1 ; link to next driver dw 0 ; device attribute word dw strat ; device "Strategy" entry point dw intr ; device "Interrupt" entry point db 1 ; number of units, this device db 7 dup (0) ; reserved (block drivers) rqptr dd ? ; far pointer to request packet savesp dw 0 ; save kernel SS:SP during switch savess dw 0 ; to driver's private stack xmm dd 0 ; address of XMM entry point handle dw 0 ; handle for extended memory block total dw 0 ; total extended mem available (KB) largest dw 0 ; largest free block available (KB) alloc dw 0 ; extended memory allocated (KB) clust dw 0 ; total clusters in RAMdisk xfersec dw 0 ; current sector for transfer xfercnt dw 0 ; sectors successfully transferred xferreq dw 0 ; number of sectors requested array dw bpb ; array of pointers to BPBs ; for each logical unit movpars equ $ ; XMS Function 0BH parameter block movelen dd 0 ; length to move in bytes shandle dw 0 ; source handle soffset dd 0 ; source offset or far pointer dhandle dw 0 ; destination handle doffset dd 0 ; destination offset or far pointer bootrec equ $ ; boot record for logical sec. 0 jmp $ ; phony JMP at start of boot nop ; sector (must be 3 bytes) db 'IBM 3.3' ; OEM identity field ; BIOS Parameter Block (BPB) bpb dw secsize ; 0 bytes per sector db 2 ; 2 sectors per cluster dw 1 ; 3 reserved sectors db 1 ; 5 number of FATs dw dirsize ; 6 root directory entries dw 0 ; 8 total sectors db 0f8h ; 0AH medium descriptor byte dw 0 ; 0BH sectors per FAT bootrec_len equ $-bootrec ; length of boot record even ; force word alignment dw 128 dup (0) stk equ $ ; local stack for driver ; ; Driver 'strategy' routine; called by MS-DOS kernel with ; ES:BX pointing to driver request packet. ; strat proc far ; driver 'strategy' routine mov word ptr cs:rqptr,bx ; save request packet address mov word ptr cs:rqptr+2,es ret ; back to MS-DOS kernel strat endp ; ; Driver 'interrupt' routine, called by MS-DOS kernel immediately ; after call to 'strategy' routine to process I/O request. ; intr proc far push ax ; save all registers push bx push cx push dx push ds push es push di push si push bp mov ax,cs ; make local data addressable mov ds,ax mov savess,ss ; save DOS kernel's stack mov savesp,sp mov ss,ax ; set SS:SP to point to mov sp,offset stk ; (larger) local stack les di,rqptr ; ES:DI = request packet mov bl,es:[di.command] ; get BX = command code xor bh,bh cmp bx,maxcmd ; make sure it's legal jle intr1 ; jump, function code is ok mov ax,8003h ; return 'unknown command' error jmp intr2 intr1: shl bx,1 ; branch to command code routine call word ptr [bx+dispch] ; must return AX = status les di,rqptr ; ES:DI = request packet again intr2: or ax,0100h ; merge 'done' bit into status mov es:[di.status],ax ; store into request packet mov ss,savess ; restore DOS kernel's stack mov sp,savesp pop bp ; restore general registers pop si pop di pop es pop ds pop dx pop cx pop bx pop ax ret ; back to kernel intr endp ; ; Dispatch table for driver commands ; dispch dw init ; 0 = initialize driver dw medchk ; 1 = media check on block device dw bldbpb ; 2 = build BIOS parameter block dw error ; 3 = I/O control read dw read ; 4 = read from device dw error ; 5 = non-destructive read dw error ; 6 = return current input status dw error ; 7 = flush device input buffers dw write ; 8 = write to device dw write ; 9 = write with verify dw error ; 10 = return current output status dw error ; 11 = flush output buffers dw error ; 12 = I/O control write dw error ; 13 = device open (DOS 3.0+) dw error ; 14 = device close (DOS 3.0+) dw error ; 15 = removeable media (DOS 3.0+) dw error ; 16 = output until busy (DOS 3.0+) dw error ; 17 = not used dw error ; 18 = not used dw error ; 19 = generic IOCTL (DOS 3.2+) dw error ; 20 = not used dw error ; 21 = not used dw error ; 22 = not used dw error ; 23 = get logical device (DOS 3.2+) dw error ; 24 = set logical device (DOS 3.2+) ; ; Media Check routine (command code 1). Returns code indicating ; whether medium has been changed since last access. ; medchk proc near mov byte ptr es:[di+14],1 ; return "not changed" code xor ax,ax ; return success status ret medchk endp ; ; Build BPB routine (command code 2). Returns pointer to valid ; BIOS Parameter Block for logical drive. ; bldbpb proc near mov word ptr es:[di+20],cs ; put BPB address in packet mov word ptr es:[di+18],offset bpb xor ax,ax ; return success status ret bldbpb endp ; ; Read routine (command code 4). Transfers logical sector(s) ; from RAMdisk storage to specified address. ; read proc near mov ax,es:[di.sector] ; ES:DI = request packet mov xfersec,ax ; save starting sector number mov ax,es:[di.count] mov xferreq,ax ; save sectors requested mov xfercnt,0 ; init sectors transferred count mov ax,word ptr es:[di.address] mov word ptr doffset,ax ; requestor's buffer address mov ax,word ptr es:[di.address+2] mov word ptr doffset+2,ax mov ax,handle ; source handle = extended mov shandle,ax ; memory handle mov dhandle,0 ; destination handle = 0 mov word ptr movelen,secsize; logical sector length read1: mov ax,xfercnt ; done with all sectors yet? cmp ax,xferreq je read2 ; jump if transfer completed mov ax,xfersec ; source offset = mul bpb ; sector no. * bytes/sector mov word ptr soffset,ax mov word ptr soffset+2,dx mov ah,0bh ; move this sector from mov si,offset movpars ; extended memory to requestor call xmm or ax,ax ; any error? jz read4 ; yes, abort transfer inc xfersec ; advance sector and address add word ptr doffset+2,(secsize/16) inc xfercnt ; count sectors transferred jmp read1 read2: ; all sectors transferred, xor ax,ax ; return success status read3: les di,rqptr ; get address of request packet mov bx,xfercnt ; return sectors transferred count mov es:[di.count],bx ret read4: mov ax,800bh ; XMM error, return 'read fault' jmp read3 read endp ; ; Write (command code 8) and Write with Verify (command code 9) ; routine. Transfers logical sector(s) from specified address ; to RAMdisk storage. ; write proc near mov ax,es:[di.sector] ; ES:DI = request packet mov xfersec,ax ; save starting sector number mov ax,es:[di.count] mov xferreq,ax ; save sectors requested mov xfercnt,0 ; init sectors transferred count mov ax,word ptr es:[di.address] mov word ptr soffset,ax ; requestor's buffer address mov ax,word ptr es:[di.address+2] mov word ptr soffset+2,ax mov ax,handle ; destination handle = extended mov dhandle,ax ; memory handle mov shandle,0 ; zero out source handle mov word ptr movelen,secsize; logical sector length write1: mov ax,xfercnt ; done with all sectors yet? cmp ax,xferreq je write2 ; jump if transfer completed mov ax,xfersec ; destination offset = mul bpb ; sector no. * bytes/sector mov word ptr doffset,ax mov word ptr doffset+2,dx mov ah,0bh ; move this sector from mov si,offset movpars ; requestor to extended memory call xmm or ax,ax ; any error? jz write4 ; yes, abort transfer inc xfersec ; advance sector and address add word ptr soffset+2,(secsize/16) inc xfercnt ; count sectors transferred jmp write1 write2: ; all sectors successfully xor ax,ax ; transferred, return ok status write3: les di,rqptr ; get address of request packet mov bx,xfercnt ; return actual transfer count mov es:[di.count],bx ret write4: mov ax,800ah ; XMM error, return 'write fault' jmp write3 write endp ; ; Dummy routine for unsupported driver command codes ; error proc near mov ax,8103h ; return 'unknown command' error ret error endp ; ; Initialization routine, called at driver load time. Returns ; address of 'init' label to MS-DOS as start of free memory, so ; that memory occupied by 'init' and its subroutines is reclaimed. ; init proc near ; command code 0 = initialize mov ax,4300h ; check if XMM present int 2fh cmp al,80h ; status = installed? je init1 ; yes, proceed mov dx,offset msg1 ; no, display error message jmp init8 ; and abort installation init1: mov ax,4310h ; XMM available, request entry int 2fh ; point and save it mov word ptr xmm,bx mov word ptr xmm+2,es mov ah,8 ; get available extended memory call xmm ; transfer to XMM mov total,dx ; save total KB available mov largest,ax ; save largest free block cmp largest,64 ; at least 64 KB available? jae init2 ; yes, proceed mov dx,offset msg2 ; no, display error message jmp init8 ; and abort installation init2: les di,rqptr ; let ES:DI = request packet lds si,es:[di+18] ; point to CONFIG.SYS line init3: lodsb ; scan for end of driver name cmp al,blank ja init3 ; loop while within name dec si ; point to delimiter and call atoi ; convert size parameter push cs ; make our data addressable pop ds or ax,ax ; size parameter missing? jz init4 ; yes, use all extended memory cmp ax,largest ; requested > available? jna init5 ; no, jump init4: mov ax,largest ; use all of available memory init5: mov alloc,ax ; save requested size mov dx,ax ; DX = RAMdisk size in KB mov ah,9 ; XMS function 9 = allocate call xmm ; transfer to XMM or ax,ax ; allocation successful? jnz init6 ; yes, proceed mov dx,offset msg3 ; no, display error message jmp init8 ; and abort installation init6: mov handle,dx ; save extended memory handle call makebpb ; set up Bios Parameter Block call format ; format the RAMdisk jnc init7 ; jump if no error during format mov dx,offset msg4 ; formatting error, exit jmp init8 init7: les di,rqptr ; let ES:DI = request packet mov al,es:[di+22] ; get drive code from header, add al,'A' ; convert to ASCII for output mov ident1,al mov ax,total ; convert KB available to ASCII mov si,offset ident2 mov cx,10 call itoa mov ax,largest ; convert KB largest free block mov si,offset ident3 call itoa mov ax,alloc ; convert KB allocated to ASCII mov si,offset ident4 call itoa mov dx,offset ident ; display sign-on message mov ah,9 ; function 9 = display string int 21h ; transfer to MS-DOS ; set top of driver address mov word ptr es:[di.address],offset init mov word ptr es:[di.address+2],cs mov byte ptr es:[di+13],1 ; indicate 1 logical unit mov word ptr es:[di+20],cs ; return address of BPB array mov word ptr es:[di+18],offset array jmp init9 init8: ; XMSDISK initialization failed push dx ; save specific error message mov dx,offset errmsg ; display error heading mov ah,9 ; function 9 = display string int 21h ; transfer to MS-DOS pop dx ; display error description mov ah,9 ; function 9 = display string int 21h ; transfer to MS-DOS les di,cs:rqptr ; let ES:DI=request packet ; set driver end = driver start mov word ptr es:[di.address],0 mov word ptr es:[di.address+2],cs mov byte ptr es:[di+13],0 ; set no. of logical units = 0 init9: xor ax,ax ; return success status ret init endp ; ; Set up total sectors and sectors per FAT fields of BIOS Parameter ; Block according to size of RAMdisk. Calculate and save total ; clusters (indicates whether 12-bit or 16-bit FAT will be used). ; makebpb proc near mov ax,alloc ; get size of allocated block mov dx,1024 ; convert KB to bytes mul dx ; divided by bytes/sector div word ptr bpb ; gives AX = total sectors mov bpb+8,ax ; update BPB with total sectors xor dx,dx ; sectors / (sectors/cluster) xor ch,ch ; = total clusters mov cl,byte ptr bpb+2 div cx mov clust,ax ; save total clusters cmp ax,4086 ; clusters < 4087? jna makeb1 ; yes, jump shl ax,1 ; no, assume 16-bit FAT jmp makeb2 ; clusters * 2 = bytes/FAT makeb1: mov dx,ax ; if clusters < 4087, 12-bit FAT add ax,ax ; clusters * 1.5 = bytes/FAT add ax,dx shr ax,1 jnc makeb2 inc ax ; round bytes up if necessary makeb2: xor dx,dx ; (bytes/FAT) / (bytes/sec) div word ptr bpb ; = sectors/FAT or dx,dx ; any remainder? jz makeb3 ; no,jump inc ax ; round up to next sector makeb3: mov bpb+0bh,ax ; update FAT size in BPB ret makebpb endp ; ; Format RAMdisk. First write zeros into all sectors of reserved ; area, FAT, and root directory. Then copy phony boot record to ; boot sector, initialize medium ID byte at beginning of FAT, and ; place phony volume label in first sector of root directory. ; format proc near push ds ; initialize sector buffer pop es ; to zeros so we can clear mov di,offset secbuf ; out reserved area, FAT, mov cx,secsize ; and root directory xor al,al rep stosb mov ax,bpb+6 ; no. of directory entries mov cx,32 ; * (32 bytes/entry) mul cx ; = bytes in root directory div bpb ; / (bytes/sector) or dx,dx ; = sectors in root directory jz fmt1 inc ax ; round up any partial sector fmt1: add ax,bpb+3 ; + reserved sectors add ax,bpb+0bh ; + sectors in FAT mov xferreq,ax ; = total sectors to clear mov xfercnt,0 ; initialize sector counter ; set up move parameter block mov word ptr movelen,secsize; length to move mov shandle,0 ; source handle and address mov word ptr soffset,offset secbuf mov word ptr soffset+2,cs mov ax,handle ; destination extended memory mov dhandle,ax ; block handle mov word ptr doffset,0 ; initial destination offset mov word ptr doffset+2,0 fmt2: mov ah,0bh ; write this sector mov si,offset movpars ; DS:SI = parameter block call xmm ; transfer to XMM or ax,ax ; test move status jnz fmt3 jmp fmt5 ; abort if move failed fmt3: add word ptr doffset,secsize; increment destination address adc word ptr doffset+2,0 mov ax,xfercnt ; count sectors initialized inc ax mov xfercnt,ax cmp ax,xferreq ; done yet? jne fmt2 ; not done, write another mov ax,bpb+3 ; calculate offset of first mul bpb ; FAT sector in RAMdisk buffer mov word ptr doffset,ax ; set destination address mov word ptr doffset+2,dx mov al,byte ptr bpb+0ah ; set up medium ID byte mov secbuf,al ; in first FAT sector mov word ptr secbuf+1,-1 ; assume 12-bit FAT cmp clust,4086 ; more than 4086 clusters? jna fmt4 ; no, jump mov secbuf+3,0ffh ; yes, use 16-bit FAT fmt4: mov ah,0bh ; write first FAT sector mov si,offset movpars call xmm or ax,ax ; test move status jz fmt5 ; abort if move failed mov word ptr doffset,0 ; offset of logical sector 0 mov word ptr doffset+2,0 mov word ptr soffset,offset bootrec mov word ptr movelen,bootrec_len mov ah,0bh ; copy phony boot record mov si,offset movpars ; to logical sector 0 call xmm or ax,ax ; test move status jz fmt5 ; abort if move failed mov ax,bpb+0bh ; calculate offset of first add ax,bpb+3 ; root directory sector mul bpb ; in RAMdisk buffer mov word ptr doffset,ax mov word ptr doffset+2,dx mov word ptr soffset,offset volname mov word ptr movelen,volname_len mov ah,0bh ; copy phony volume label mov si,offset movpars ; to first directory sector call xmm or ax,ax ; test move status jz fmt5 ; abort if move failed clc ; successful format, ret ; return CY = clear fmt5: stc ; format failed, ret ; return CY = set format endp ; ; Miscellaneous data used during initialization, then discarded. ; ident db cr,lf,lf ; sign-on message db 'XMSDISK Extended Memory RAMdisk' db cr,lf db 'Copyright (C) 1989 Ziff Davis Communications' db cr,lf db 'PC Magazine * Ray Duncan' db cr,lf,lf db 'XMSDISK will be drive ' ident1 db 'X:',cr,lf db 'Extended memory available:' ident2 db ' KB',cr,lf db 'Largest free memory block:' ident3 db ' KB',cr,lf db 'Extended memory allocated:' ident4 db ' KB',cr,lf,eom errmsg db cr,lf db 'XMSDISK installation error:' db cr,lf,eom msg1 db 'Extended Memory Manager not found.' db cr,lf,eom msg2 db 'Insufficient extended memory available.' db cr,lf,eom msg3 db 'Extended memory allocation failed.' db cr,lf,eom msg4 db 'Unable to format RAMdisk.' db cr,lf,eom volname db 'XMSDISK ' ; phony volume label db 08h ; volume label attribute byte db 10 dup (0) dw 0 ; time = 00:00:00 dw 1241h ; date = February 1, 1989 db 6 dup (0) volname_len equ $-volname secbuf db secsize dup (?) ; sector buffer for format _TEXT ends end