Microsoft Programmer's Library 1.3

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Assembly Source File | 1988-12-12 | 21.3 KB | 615 lines

title TINYDISK -- RAM Disk Device Driver page 55,132 .286 ; ; TINYDISK.ASM ; ; A sample OS/2 block device driver that installs a 64 KB RAM disk. ; ; Assemble with: C> masm tinydisk.asm; ; Link with: C> link tinydisk,tinydisk.sys,,os2,tinydisk ; ; To install the driver, add "DEVICE=TINYDISK.SYS" to CONFIG.SYS ; and reboot. ; ; Copyright (C) 1988 Ray Duncan ; maxcmd equ 26 ; maximum allowed command code secsize equ 512 ; bytes/sector, IBM compatible media stdin equ 0 ; standard device handles stdout equ 1 stderr equ 2 cr equ 0dh ; ASCII carriage return lf equ 0ah ; ASCII linefeed PhysToVirt equ 15h ; DevHlp services UnPhysToVirt equ 32h VerifyAccess equ 27h AllocPhys equ 18h extrn DosWrite:far DGROUP group _DATA _DATA segment word public 'DATA' ; device driver header... header dd -1 ; link to next device driver dw 0080h ; device attribute word ; bits 7-9 = driver level dw Strat ; Strategy entry point dw 0 ; reserved db 0 ; units (set by OS/2) db 15 dup (0) ; reserved devhlp dd ? ; DevHlp entry point wlen dw ? ; receives DosWrite length dbase dd ? ; 32-bit physical address, ; base of RAM disk storage xfrsec dw 0 ; current sector for transfer xfrcnt dw 0 ; sectors successfully transferred xfrreq dw 0 ; number of sectors requested xfraddr dd 0 ; working address for transfer array dw bpb ; array of pointers to BPB ; for each supported unit bootrec equ $ ; logical sector 0 boot record jmp $ ; JMP at start of boot sector, nop ; this field must be 3 bytes db 'IBM 10.1' ; OEM identity field ; ---BIOS Parameter Block----- bpb dw secsize ; 00H bytes per sector db 1 ; 02H sectors per cluster dw 1 ; 03H reserved sectors db 1 ; 05H number of FATs dw 64 ; 06H root directory entries dw 128 ; 08H total sectors db 0f8h ; 0AH media descriptor dw 1 ; 0BH sectors per FAT dw 1 ; 0DH sectors per track dw 1 ; 0FH number of heads dd 0 ; 11H hidden sectors dd 0 ; 15H large total sectors (if ; word at offset 08H = 0) db 6 dup (0) ; 19H reserved ; ---End of BPB, 31 bytes----- bootrec_len equ $-bootrec ; length of boot sector data ; additional words needed by ; Generic IOCTL Cat 8 Function 63H ; Get Device Parameters call dw 0 ; number of cylinders db 7 ; device type = unknown dw 1 ; device attribute word gdprec_len equ $-bpb ; length of Generic IOCTL buffer ; Strategy routine dispatch table ; for request packet command code... dispch dw Init ; 0 = initialize driver dw MediaChk ; 1 = media check on block device dw BuildBPB ; 2 = build BIOS parameter block dw Error ; 3 = reserved dw Read ; 4 = read (input) from device dw Error ; 5 = nondestructive read dw Error ; 6 = return input status dw Error ; 7 = flush device input buffers dw Write ; 8 = write (output) to device dw Write ; 9 = write with verify dw Error ; 10 = return output status dw Error ; 11 = flush output buffers dw Error ; 12 = reserved dw Error ; 13 = device open dw Error ; 14 = device close dw Error ; 15 = removable media dw GenIOCTL ; 16 = generic IOCTL dw Error ; 17 = reset media dw GSLogDrv ; 18 = get logical drive dw GSLogDrv ; 19 = set logical drive dw Error ; 20 = deinstall dw Error ; 21 = reserved dw Error ; 22 = partitionable fixed disks dw Error ; 23 = get fixed disk unit map dw Error ; 24 = reserved dw Error ; 25 = reserved dw Error ; 26 = reserved ; start of data discarded ; after initialization ident db cr,lf,lf ; successful installation message... db 'TINYDISK 64 KB RAM disk for OS/2' db cr,lf db 'RAM disk will be drive ' drive db 'X:' db cr,lf ident_len equ $-ident abort db cr,lf ; aborted installation message db 'TINYDISK installation aborted' db cr,lf abort_len equ $-abort volname db 'TINYDISK ' ; volume label for RAM disk db 08h ; attribute byte db 10 dup (0) ; reserved area dw 0 ; time = 00:00 dw 1021h ; date = January 1, 1988 db 6 dup (0) ; reserved area volname_len equ $-volname _DATA ends _TEXT segment word public 'CODE' assume cs:_TEXT,ds:DGROUP,es:NOTHING Strat proc far ; Strategy entry point ; ES:BX = request packet mov di,es:[bx+2] ; get command code from packet and di,0ffh cmp di,maxcmd ; supported by this driver? jle Strat1 ; jump if command code OK call Error ; bad command code jmp Strat2 Strat1: add di,di ; go to command code routine call word ptr [di+dispch] Strat2: ; return with AX = status mov es:[bx+3],ax ; put status in request packet ret ; return to OS/2 kernel Strat endp ; Command code routines are called by the Strategy routine ; via the Dispatch table with ES:BX pointing to the request ; header. Each routine should return ES:BX unchanged, ; and AX = status to be placed in request packet: ; 0100H if 'done' and no error ; 0000H if thread should block pending interrupt ; 81xxH if 'done' and error detected (xx = error code) MediaChk proc near ; function 1 = media check ; return 'not changed' code mov byte ptr es:[bx+0eh],1 mov ax,0100h ; return 'done' status ret MediaChk endp BuildBPB proc near ; function 2 = build BPB ; put BPB address into ; request packet mov word ptr es:[bx+12h],offset DGROUP:bpb mov word ptr es:[bx+14h],ds mov ax,0100h ; return 'done' status ret BuildBPB endp Read proc near ; function 4 = read push es ; save request packet address push bx call setup ; set up transfer variables Read1: mov ax,xfrcnt ; done with all sectors yet? cmp ax,xfrreq je read2 ; jump if transfer completed mov ax,ds ; set ES = DGROUP mov es,ax mov ax,xfrsec ; get sector number call MapDS ; and map it to DS:SI ; (may force mode switch) push es ; save DGROUP selector ; convert destination physical ; address to virtual address... mov bx,word ptr es:xfraddr mov ax,word ptr es:xfraddr+2 mov cx,secsize ; segment length mov dh,1 ; leave result in ES:DI mov dl,PhysToVirt ; function number call es:devhlp ; transfer to kernel mov cx,secsize ; transfer logical sector from cld ; RAM disk to requestor rep movsb pop ds ; restore DGROUP addressing sti ; PhysToVirt may mask interrupts inc xfrsec ; advance sector number ; advance transfer address add word ptr xfraddr,secsize adc word ptr xfraddr+2,0 inc xfrcnt ; count sectors transferred jmp read1 Read2: ; all sectors transferred mov dl,UnPhysToVirt ; function number call devhlp ; transfer to kernel pop bx ; restore request packet address pop es mov ax,xfrcnt ; put actual transfer count mov es:[bx+12h],ax ; into request packet mov ax,0100h ; return 'done' status ret Read endp Write proc near ; functions 8,9 = write push es ; save request packet address push bx call setup ; set up transfer variables Write1: mov ax,xfrcnt ; done with all sectors yet? cmp ax,xfrreq je write2 ; jump if transfer completed mov ax,xfrsec ; get sector number call MapES ; map it to ES:DI ; (may force mode switch) push ds ; save DGROUP selector ; convert source physical ; address to virtual address... mov bx,word ptr xfraddr mov ax,word ptr xfraddr+2 mov cx,secsize ; segment length mov dh,0 ; leave result in DS:SI mov dl,PhysToVirt ; function number call devhlp ; transfer to kernel mov cx,secsize ; transfer logical sector from cld ; requestor to RAM disk rep movsb pop ds ; restore DGROUP addressing sti ; PhysToVirt might have masked inc xfrsec ; advance sector number ; advance transfer address add word ptr xfraddr,secsize adc word ptr xfraddr+2,0 inc xfrcnt ; count sectors transferred jmp write1 Write2: ; all sectors transferred mov dl,UnPhysToVirt ; function number call devhlp ; transfer to kernel pop bx ; restore request packet address pop es mov ax,xfrcnt ; put actual transfer count mov es:[bx+12h],ax ; into request packet mov ax,0100h ; return 'done' status ret Write endp GenIOCTL proc near ; function 16 = generic IOCTL push es ; save request packet address push bx mov ax,8103h ; assume unknown command ; Get Device Parameters call? cmp byte ptr es:[bx+0dh],8 jne Gen9 ; no, set 'done' + 'error' cmp byte ptr es:[bx+0eh],63h jne Gen9 ; no, set 'done' + 'error' ; verify user's access mov ax,es:[bx+15h] ; selector mov di,es:[bx+13h] ; offset mov cx,gdprec_len ; length to be written mov dh,1 ; need read/write access mov dl,VerifyAccess ; function number call devhlp ; transfer to kernel mov ax,810ch ; if no access, exit with jc Gen9 ; 'done' + general failure ; get destination address les di,dword ptr es:[bx+13h] ; copy device info to caller mov si,offset DGROUP:bpb mov cx,gdprec_len ; length of parameter block cld rep movsb mov ax,0100h ; set 'done' status Gen9: pop bx ; restore request packet address pop es ret ; and return with status GenIOCTL endp GSLogDrv proc near ; function 18, 19 = get ; or set logical drive ; return code indicating there ; are no logical drive aliases mov byte ptr es:[bx+1],0 mov ax,0100h ; return 'done' status ret GSLogDrv endp Error proc near ; bad command code mov ax,8103h ; error bit + 'done' status ret ; + "Unknown Command" code Error endp MapES proc near ; map sector number to ; virtual memory address ; call with AX = logical sector ; return ES:DI = memory address ; and Carry clear ; or Carry set if error mov di,secsize ; bytes per sector mul di ; * logical sector number xchg ax,dx ; AX:BX := 32-bit physical mov bx,dx ; sector address add bx,word ptr dbase adc ax,word ptr dbase+2 mov cx,secsize mov dh,1 ; result to ES:DI mov dl,PhysToVirt ; function number call devhlp ; transfer to kernel ret ; return ES:DI = sector address MapES endp MapDS proc near ; map sector number to ; virtual memory address ; call with AX = logical sector ; return DS:SI = memory address ; and Carry clear ; or Carry set if error mov si,secsize ; bytes per sector mul si ; * logical sector number xchg ax,dx ; AX:BX := 32-bit physical mov bx,dx ; sector address add bx,word ptr dbase adc ax,word ptr dbase+2 mov cx,secsize mov dh,0 ; result to DS:SI mov dl,PhysToVirt ; function number call devhlp ; transfer to kernel ret ; return DS:SI = sector address MapDS endp Setup proc near ; set up for read/write ; ES:BX = request packet ; extracts address, start, count mov ax,es:[bx+14h] ; starting sector number mov xfrsec,ax mov ax,es:[bx+12h] ; sectors requested mov xfrreq,ax mov ax,es:[bx+0eh] ; requestor's buffer address mov word ptr xfraddr,ax mov ax,es:[bx+10h] mov word ptr xfraddr+2,ax mov xfrcnt,0 ; initialize sectors ; transferred counter ret Setup endp ; start of code discarded ; after initialization Init proc near ; function 0 = initialize mov ax,es:[bx+0eh] ; get DevHlp entry point mov word ptr devhlp,ax mov ax,es:[bx+10h] mov word ptr devhlp+2,ax mov al,es:[bx+16h] ; unit code for this drive add al,'A' ; convert to ASCII and place mov drive,al ; in output string ; display sign-on message... push stdout ; handle for standard output push ds ; address of message push offset DGROUP:ident push ident_len ; length of message push ds ; receives bytes written push offset DGROUP:wlen call DosWrite ; set offsets to end of code ; and data segments mov word ptr es:[bx+0eh],offset _TEXT:Init mov word ptr es:[bx+10h],offset DGROUP:ident ; logical units supported mov byte ptr es:[bx+0dh],1 ; pointer to BPB array mov word ptr es:[bx+12h],offset DGROUP:array mov word ptr es:[bx+14h],ds push es ; save request packet address push bx ; allocate RAM disk storage mov bx,0 ; AX:BX = size of allocated mov ax,1 ; block in bytes mov dh,0 ; request block above 1 MB mov dl,AllocPhys ; function number call devhlp ; transfer to kernel jc Init9 ; jump if allocation failed ; save physical address ; of allocated block mov word ptr dbase,bx mov word ptr dbase+2,ax call format ; format the RAM disk jc Init9 ; jump if format failed pop bx ; restore request packet address pop es mov ax,0100h ; return 'done' status ret Init9: ; abort driver installation pop bx ; restore request packet address pop es ; display installation aborted... push stdout ; handle for standard output push ds ; address of message push offset DGROUP:abort push abort_len ; length of message push ds ; receives bytes written push offset DGROUP:wlen call DosWrite ; transfer to OS/2 ; set zero units mov byte ptr es:[bx+0dh],0 ; set lengths of code and ; data segments mov word ptr es:[bx+0eh],0 mov word ptr es:[bx+10h],0 mov ax,810ch ; return error + done + ; general failure ret Init endp Format proc near ; format the RAM disk area ; calculate length of ; RAM disk control areas mov al,byte ptr bpb+5 cbw ; number of FATs mov cx,bpb+0bh ; * sectors per FAT mul cx mov cx,bpb+6 ; entries in root directory shr cx,4 ; divided by 16 for sectors add ax,cx ; (FAT + dir sectors add ax,bpb+3 ; + reserved sectors) mov cx,secsize ; * bytes/sector mul cx ; = total length mov cx,ax ; convert RAM disk base to ; virtual address mov bx,word ptr dbase mov ax,word ptr dbase+2 mov dh,1 ; leave result in ES:DI mov dl,PhysToVirt ; function number call devhlp ; transfer to kernel jc Format9 ; jump if error xor ax,ax ; now zero control areas cld ; (assume CX still = length) rep stosb mov ax,0 ; get address of logical call MapES ; sector zero jc Format9 ; jump if error mov si,offset DGROUP:bootrec mov cx,bootrec_len ; copy boot record rep movsb ; to logical sector zero mov ax,word ptr bpb+3 call MapES ; get address of FAT sector jc Format9 ; jump if error mov al,byte ptr bpb+0ah mov es:[di],al ; media ID byte into FAT mov word ptr es:[di+1],-1 mov ax,word ptr bpb+3 add ax,word ptr bpb+0bh call MapES ; get address of directory jc Format9 ; jump if error mov si,offset DGROUP:volname mov cx,volname_len rep movsb ; copy volume label to it mov dl,UnPhysToVirt ; function number call devhlp ; transfer to kernel clc ; signal format successful Format9: ; return with Carry = 0 ret ; if success, 1 if error Format endp _TEXT ends end