Reverse Code Engineering RCE CD +sandman 2000

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Assembly Source File | 1994-07-28 | 17.9 KB | 812 lines

.286 page 58, 132 name SGDI title SGDI Driver for Standard Game Adapter Card subttl This Program is Public Domain Material. ; SGDI.EXE ; ; Usage: ; SDGI ; ; This program loads a TSR which patches INT 15 so arbitrary game programs ; can read the joystick in a portable fashion. ; ; ; We need to load cseg in memory before any other segments! cseg segment para public 'code' cseg ends ; Initialization code, which we do not need except upon initial load, ; goes in the following segment: Initialize segment para public 'INIT' Initialize ends ; UCR Standard Library routines which get dumped later on. .xlist include stdlib.a includelib stdlib.lib .list sseg segment para stack 'stack' sseg ends zzzzzzseg segment para public 'zzzzzzseg' zzzzzzseg ends CSEG segment para public 'CODE' assume cs:cseg, ds:nothing wp equ <word ptr> byp equ <byte ptr> Int15Vect dd 0 PSP dw ? ; Port addresses for a typical joystick card: JoyPort equ 201h JoyTrigger equ 201h ; Data structure to hold information about each pot. ; (mainly for calibration and normalization purposes). Pot struc PotMask db 0 ;Pot mask for hardware. DidCal db 0 ;Is this pot calibrated? min dw 5000 ;Minimum pot value max dw 0 ;Max pot value center dw 0 ;Pot value in the middle Pot ends ; Variables for each of the pots. Must initialize the masks so they ; mask out all the bits except the incomming bit for each pot. Pot0 Pot <1> Pot1 Pot <2> Pot2 Pot <4> Pot3 Pot <8> ; The IDstring address gets passed back to the caller on a testpresence ; call. The four bytes before the IDstring must contain the serial number ; and current driver number. SerialNumber db 0,0,0 IDNumber db 0 IDString db "Standard SGDI Driver",0 db "Public Domain Driver Written by Randall L. Hyde",0 ;============================================================================ ; ; ReadPots- AH contains a bit mask to determine which pots we should read. ; Bit 0 is one if we should read pot 0, bit 1 is one if we should ; read pot 1, bit 2 is one if we should read pot 2, bit 3 is one ; if we should read pot 3. All other bits will be zero. ; ; This code returns the pot values in SI, BX, BP, and DI for Pot 0, 1, ; 2, & 3. ; ReadPots proc near sub bp, bp mov si, bp mov di, bp mov bx, bp ; Wait for any previous signals to finish up before trying to read this ; guy. It is possible that the last pot we read was very short. However, ; the trigger signal starts timers running for all four pots. This code ; terminates as soon as the current pot times out. If the user immediately ; reads another pot, it is quite possible that the new pot's timer has ; not yet expired from the previous read. The following loop makes sure we ; aren't measuring the time from the previous read. mov dx, JoyPort mov cx, 400h Wait4Clean: in al, dx and al, 0Fh loopnz Wait4Clean ; Okay, read the pots. The following code triggers the 558 timer chip ; and then sits in a loop until all four pot bits (masked with the pot mask ; in AL) become zero. Each time through this loop that one or more of these ; bits contain zero, this loop increments the corresponding register(s). mov dx, JoyTrigger out dx, al ;Trigger pots mov dx, JoyPort mov cx, 1000h ;Don't let this go on forever. PotReadLoop: in al, dx and al, ah jz PotReadDone shr al, 1 adc si, 0 ;Increment SI if pot 0 still active. shr al, 1 adc bx, 0 ;Increment BX if pot 1 still active. shr al, 1 adc bp, 0 ;Increment BP if pot 2 still active. shr al, 1 adc di, 0 ;Increment DI if pot 3 still active. loop PotReadLoop ;Stop, eventually, if funny hardware. and si, 0FFFh ;If we drop through to this point, and bx, 0FFFh ; one or more pots timed out (usually and bp, 0FFFh ; because they are not connected). and di, 0FFFh ; The reg contains 4000h, set it to 0. PotReadDone: ret ReadPots endp ;---------------------------------------------------------------------------- ; ; Normalize- BX contains a pointer to a pot structure, AX contains ; a pot value. Normalize that value according to the ; calibrated pot. ; ; Note: DS must point at cseg before calling this routine. assume ds:cseg Normalize proc near push cx ; Sanity check to make sure the calibration process went okay. cmp [bx].Pot.DidCal, 0 ;Is this pot calibrated? je BadNorm ;If not, quit. mov dx, [bx].Pot.Center ;Do a sanity check on the cmp dx, [bx].Pot.Min ; min, center, and max jbe BadNorm ; values to make sure cmp dx, [bx].Pot.Max ; min < center < max. jae BadNorm ; Clip the value if it is out of range. cmp ax, [bx].Pot.Min ;If the value is less than ja MinOkay ; the minimum value, set it mov ax, [bx].Pot.Min ; to the minimum value. MinOkay: cmp ax, [bx].Pot.Max ;If the value is greater than jb MaxOkay ; the maximum value, set it mov ax, [bx].Pot.Max ; to the maximum value. MaxOkay: ; Scale this guy around the center: cmp ax, [bx].Pot.Center ;See if less than or greater jb Lower128 ; than centered value. ; Okay, current reading is greater than the centered value, scale the reading ; into the range 128..255 here: sub ax, [bx].Pot.Center mov dl, ah ;Multiply by 128 mov ah, al mov dh, 0 mov al, dh shr dl, 1 rcr ax, 1 mov cx, [bx].Pot.Max sub cx, [bx].Pot.Center jz BadNorm ;Prevent division by zero. div cx ;Compute normalized value. add ax, 128 ;Scale to range 128..255. cmp ah, 0 je NormDone mov ax, 0ffh ;Result must fit in 8 bits! jmp NormDone ; If the reading is below the centered value, scale it into the range ; 0..127 here: Lower128: sub ax, [bx].Pot.Min mov dl, ah mov ah, al mov dh, 0 mov al, dh shr dl, 1 rcr ax, 1 mov cx, [bx].Pot.Center sub cx, [bx].Pot.Min jz BadNorm div cx cmp ah, 0 je NormDone mov ax, 0ffh jmp NormDone ; If something went wrong, return zero as the normalized value. BadNorm: sub ax, ax NormDone: pop cx ret Normalize endp assume ds:nothing ;============================================================================ ; INT 15h handler functions. ;============================================================================ ; ; Although these are defined as near procs, they are not really procedures. ; The MyInt15 code jumps to each of these with BX, a far return address, and ; the flags sitting on the stack. Each of these routines must handle the ; stack appropriately. ; ;---------------------------------------------------------------------------- ; BIOS- Handles the two BIOS calls, DL=0 to read the switches, DL=1 to ; read the pots. For the BIOS routines, we'll ignore the cooley ; switch (the hat) and simply read the other four switches. BIOS proc near cmp dl, 1 ;See if switch or pot routine. jb Read4Sw je ReadBIOSPots ; If not a valid BIOS call, jump to the original INT 15 handler and ; let it take care of this call. pop bx jmp cs:Int15Vect ;Let someone else handle it! ; BIOS read switches function. Read4Sw: push dx mov dx, JoyPort in al, dx and al, 0F0h ;Return only switch values. pop dx pop bx iret ; BIOS read pots function. ReadBIOSPots: pop bx ;Return a value in BX! push si push di push bp mov ah, 0Fh ;Read all four pots. call ReadPots mov ax, si mov cx, bp ;BX already contains pot 1 reading. mov dx, di pop bp pop di pop si iret BIOS endp ;---------------------------------------------------------------------------- ; ; ReadPot- On entry, DL contains a pot number to read. ; Read and normalize that pot and return the result in AL. assume ds:cseg ReadPot proc near ;;;;;;;;;; push bx ;Already on stack. push ds push cx push dx push si push di push bp mov bx, cseg mov ds, bx ; If dl = 0, read and normalize the value for pot 0, if not, try some ; other pot. cmp dl, 0 jne Try1 mov ah, Pot0.PotMask ;Get bit for this pot. call ReadPots ;Read pot 0. lea bx, Pot0 ;Pointer to pot data. mov ax, si ;Get pot 0 reading. call Normalize ;Normalize to 0..FFh. jmp GotPot ;Return to caller. ; Test for DL=1 here (read and normalize pot 1). Try1: cmp dl, 1 jne Try2 mov ah, Pot1.PotMask call ReadPots mov ax, bx lea bx, Pot1 call Normalize jmp GotPot ; Test for DL=2 here (read and normalize pot 2). Try2: cmp dl, 2 jne Try3 mov ah, Pot2.PotMask call ReadPots lea bx, Pot2 mov ax, bp call Normalize jmp GotPot ; Test for DL=3 here (read and normalize pot 3). Try3: cmp dl, 3 jne BadPot mov ah, Pot3.PotMask call ReadPots lea bx, Pot3 mov ax, di call Normalize jmp GotPot ; Bad value in DL if we drop to this point. The standard game card ; only supports four pots. BadPot: sub ax, ax ;Pot not available, return zero. GotPot: pop bp pop di pop si pop dx pop cx pop ds pop bx iret ReadPot endp assume ds:nothing ;---------------------------------------------------------------------------- ; ; ReadRaw- On entry, DL contains a pot number to read. ; Read that pot and return the unnormalized result in AX. assume ds:cseg ReadRaw proc near ;;;;;;;;;; push bx ;Already on stack. push ds push cx push dx push si push di push bp mov bx, cseg mov ds, bx ; This code is almost identical to the ReadPot code. The only difference ; is that we don't bother normalizing the result and (of course) we return ; the value in AX rather than AL. cmp dl, 0 jne Try1 mov ah, Pot0.PotMask call ReadPots mov ax, si jmp GotPot Try1: cmp dl, 1 jne Try2 mov ah, Pot1.PotMask call ReadPots mov ax, bx jmp GotPot Try2: cmp dl, 2 jne Try3 mov ah, Pot2.PotMask call ReadPots mov ax, bp jmp GotPot Try3: cmp dl, 3 jne BadPot mov ah, Pot3.PotMask call ReadPots mov ax, di jmp GotPot BadPot: sub ax, ax ;Pot not available, return zero. GotPot: pop bp pop di pop si pop dx pop cx pop ds pop bx iret ReadRaw endp assume ds:nothing ;---------------------------------------------------------------------------- ; Read4Pots- Reads pots zero, one, two, and three returning their ; values in AL, AH, DL, and DH. ; ; On entry, AL contains the pot mask to select which pots ; we should read (bit 0=1 for pot 0, bit 1=1 for pot 1, etc). Read4Pots proc near ;;;;;;;;;;; push bx ;Already on stack push ds push cx push si push di push bp mov dx, cseg mov ds, dx mov ah, al call ReadPots push bx ;Save pot 1 reading. mov ax, si ;Get pot 0 reading. lea bx, Pot0 ;Point bx at pot0 vars. call Normalize ;Normalize. mov cl, al ;Save for later. pop ax ;Retreive pot 1 reading. lea bx, Pot1 call Normalize mov ch, al ;Save normalized value. mov ax, bp lea bx, Pot2 call Normalize mov dl, al ;Pot 2 value. mov ax, di lea bx, Pot3 call Normalize mov dh, al ;Pot 3 value. mov ax, cx ;Pots 0 and 1. pop bp pop di pop si pop cx pop ds pop bx iret Read4Pots endp ;---------------------------------------------------------------------------- ; CalPot- Calibrate the pot specified by DL. On entry, AL contains ; the minimum pot value (it better be less than 256!), BX ; contains the maximum pot value, and CX contains the centered ; pot value. assume ds:cseg CalPot proc near pop bx ;Retrieve maximum value push ds push si mov si, cseg mov ds, si ; Sanity check on parameters, sort them in ascending order: mov ah, 0 cmp bx, cx ;Make sure center < max ja GoodMax xchg bx, cx GoodMax: cmp ax, cx ;Make sure min < center. jb GoodMin ; (note: may make center<max). xchg ax, cx GoodMin: cmp cx, bx ;Again, be sure center < max. jb GoodCenter xchg cx, bx GoodCenter: ; Okay, figure out who were supposed to calibrate: lea si, Pot0 cmp dl, 1 jb DoCal ;Branch if this is pot 0 lea si, Pot1 je DoCal ;Branch if this is pot 1 lea si, Pot2 cmp dl, 3 jb DoCal ;Branch if this is pot 2 jne CalDone ;Branch if not pot 3 lea si, Pot3 DoCal: mov [si].Pot.min, ax ;Store away the minimum, mov [si].Pot.max, bx ; maximum, and mov [si].Pot.center, cx ; centered values. mov [si].Pot.DidCal, 1 ;Note we've cal'd this pot. CalDone: pop si pop ds iret CalPot endp assume ds:nothing ;---------------------------------------------------------------------------- ; TestCal- Just checks to see if the pot specified by DL has already ; been calibrated. assume ds:cseg TestCal proc near ;;;;;;;; push bx ;Already on stack push ds mov bx, cseg mov ds, bx sub ax, ax ;Assume no calibration (also zeros AH) lea bx, Pot0 ;Get the address of the specified cmp dl, 1 ; pot's data structure into the jb GetCal ; BX register. lea bx, Pot1 je GetCal lea bx, Pot2 cmp dl, 3 jb GetCal jne BadCal lea bx, Pot3 GetCal: mov al, [bx].Pot.DidCal BadCal: pop ds pop bx iret TestCal endp assume ds:nothing ;---------------------------------------------------------------------------- ; ; ReadSw- Reads the switch whose switch number appears in DL. ReadSw proc near ;;;;;;; push bx ;Already on stack push cx sub ax, ax ;Assume no such switch. cmp dl, 3 ;Return if the switch number is ja NotDown ; greater than three. mov cl, dl ;Save switch to read. add cl, 4 ;Move from position four down to zero. mov dx, JoyPort in al, dx ;Read the switches. shr al, cl ;Move desired switch bit into bit 0. xor al, 1 ;Invert so sw down=1. and ax, 1 ;Remove other junk bits. NotDown: pop cx pop bx iret ReadSw endp ;---------------------------------------------------------------------------- ; ; Read16Sw- Reads all four switches and returns their values in AX. Read16Sw proc near ;;;;;;;; push bx ;Already on stack mov dx, JoyPort in al, dx shr al, 4 xor al, 0Fh ;Invert all switches. and ax, 0Fh ;Set other bits to zero. pop bx iret Read16Sw endp ;**************************************************************************** ; ; MyInt15- Patch for the BIOS INT 15 routine to control reading the ; joystick. MyInt15 proc far push bx cmp ah, 84h ;Joystick code? je DoJoystick OtherInt15: pop bx jmp cs:Int15Vect DoJoystick: mov bh, 0 mov bl, dh cmp bl, 80h jae VendorCalls cmp bx, JmpSize jae OtherInt15 shl bx, 1 jmp wp cs:jmptable[bx] jmptable word BIOS word ReadPot, Read4Pots, CalPot, TestCal word ReadRaw, OtherInt15, OtherInt15 word ReadSw, Read16Sw JmpSize = ($-jmptable)/2 ; Handle vendor specific calls here. VendorCalls: je RemoveDriver cmp bl, 81h je TestPresence pop bx jmp cs:Int15Vect ; TestPresence- Returns zero in AX and a pointer to the ID string in ES:BX TestPresence: pop bx ;Get old value off stack. sub ax, ax mov bx, cseg mov es, bx lea bx, IDString iret ; RemoveDriver- If there are no other drivers loaded after this one in ; memory, disconnect it and remove it from memory. RemoveDriver: push ds push es push ax push dx mov dx, cseg mov ds, dx ; See if we're the last routine patched into INT 15h mov ax, 3515h int 21h cmp bx, offset MyInt15 jne CantRemove mov bx, es cmp bx, wp seg MyInt15 jne CantRemove mov ax, PSP ;Free the memory we're in mov es, ax push es mov ax, es:[2ch] ;First, free env block. mov es, ax mov ah, 49h int 21h pop es ;Now free program space. mov ah, 49h int 21h lds dx, Int15Vect ;Restore previous int vect. mov ax, 2515h int 21h CantRemove: pop dx pop ax pop es pop ds pop bx iret MyInt15 endp cseg ends Initialize segment para public 'INIT' assume cs:Initialize, ds:cseg Main proc mov ax, cseg ;Get ptr to vars segment mov es, ax mov es:PSP, ds ;Save PSP value away mov ds, ax mov ax, zzzzzzseg mov es, ax mov cx, 100h meminit2 print byte "╓───────────────────────────────────────╖",cr,lf byte "║ Standard Game Device Interface driver ║",cr,lf byte "║ PC Compatible Game Adapter Cards ║",cr,lf byte "║ Written by Randall Hyde ║",cr,lf byte "╙───────────────────────────────────────╜",cr,lf byte cr,lf byte "'SGDI REMOVE' removes the driver from memory",cr,lf byte lf byte 0 mov ax, 1 argv ;If no parameters, empty str. stricmpl byte "REMOVE",0 jne NoRmv mov dh, 81h ;Remove opcode. mov ax, 84ffh int 15h ;See if we're already loaded. test ax, ax ;Get a zero back? jz Installed print byte "SGDI driver is not present in memory, REMOVE " byte "command ignored.",cr,lf,0 mov ax, 4c01h ;Exit to DOS. int 21h Installed: mov ax, 8400h mov dh, 80h ;Remove call int 15h mov ax, 8400h mov dh, 81h ;TestPresence call int 15h cmp ax, 0 je NotRemoved print byte "Successfully removed SGDI driver from memory." byte cr,lf,0 mov ax, 4c01h ;Exit to DOS. int 21h NotRemoved: print byte "SGDI driver is still present in memory.",cr,lf,0 mov ax, 4c01h ;Exit to DOS. int 21h NoRmv: ; Okay, Patch INT 15 and go TSR at this point. SwappedLeft: mov ax, 3515h int 21h mov wp Int15Vect, bx mov wp Int15Vect+2, es mov dx, cseg mov ds, dx mov dx, offset MyInt15 mov ax, 2515h int 21h mov dx, cseg mov ds, dx mov dx, seg Initialize sub dx, ds:psp add dx, 2 mov ax, 3100h ;Do TSR int 21h Main endp Initialize ends sseg segment para stack 'stack' dw 128 dup (0) endstk dw ? sseg ends zzzzzzseg segment para public 'zzzzzzseg' db 16 dup (0) zzzzzzseg ends end Main