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Assembly Source File | 1991-11-27 | 14.4 KB | 404 lines

;------------------------------------------------------------------- ; ; PROGRAM Use!UMBs.sys - UMB manager for PC/XT/ATs ; ; PURPOSE This program creates a device driver that will handle ; calls for Upper Memory Blocks. In doing so, it gives ; you the possibility to save conventional memory by ; storing device drivers and resident programs in the ; UMBs and hence save conventional memory. ; ; REQUIRES It will work on any PC/XT/AT or higher, either with or ; without extended memory. What you obviously *must* have ; are UMBs, and MS-DOS Version 5.0. ; ; AUTHOR Marco van Zwetselaar Phone: **-31-30-313128 ; Oorsprongpark 5 FidoNet: Marco van.Zwetselaar ; 3581 ES Utrecht NetMail 2:281/701 ; The Netherlands Utrecht, 7 Nov 1991 ; ;------------------------------------------------------------------- ; ; IMPORTANT NOTE to the programmer ; ; I am only a beginner in assembly language, and haven't found out ; as yet how to create a .com file. When you recompile this program, ; take care you do that as a com file, and then rename it to a .sys ; file. ; ; I used an alternative method that you may use as well: I compiled ; it to .exe format and then removed the first (half?) sector. In ; fact, the first bytes in the final file should be: ; ; FF FF FF FF 00 E0 ... ; ; which are the bytes that start at nextDev. (Almost any device ; driver file should start with the first two words being FFFF (-1)). ; ;==================================================================== ; ; THE ACTUAL ASSEMBLY CODE ; ;--------------------------------------------- ; This is the structure of the request header; not stored in file ; rh segment at 0 org 02h rh_cmd db ? ;command-code rh_status dw ? ;return-code org 0Eh rh0_brk_ofs dw ? ;end of driver offset rh0_brk_seg dw ? ;end of driver segment rh ends ; ;-------------------------------------------- ; The driverheader org 0h zwetsUMB segment public assume cs:zwetsumb, es:rh, ds:nothing ; any device driver will start with the following info: next_dev dd -1 attribute dw 0E000h strategy dw strat interrupt dw intr dev_name db 'I_LOVE_M' ;-------------------------------------------- ; Storage space for pointer to Request Header hdrptr label word dw ?,? ;-------------------------------------------- ; Strategy: store pointer to Request Header: strat proc far mov [hdrptr],bx mov [hdrptr]+2,es retf strat endp ;-------------------------------------------- ; Interrupt: The routine that fires the installrequest intr proc far push ax push bx push es pushf les bx, dword ptr [hdrptr] ;point es:bx to ReqHeader mov [bx].rh0_brk_seg, cs ;and already return the seg ; Remember that the device will only answer the init-request ; which is called by dos as it installs the driver. ; Any later calls will be ignored - they are not needed anyway. mov al, es:[bx].rh_cmd ;commandcode into al or al, al ;is it 0 (=init)? jnz other ; no => get off jmp inst ; yes => install other: cmp al, 10h ;is it legal call? jbe short dos ; yes => "Sorry" mov ax, 8003h ; no => "Unknown command" jmp short exit dos: xor ax, ax ;"Sorry - not implememented" exit: or ax, 0100h ;Set done bit mov es:[bx].rh_status, ax ;set return code popf pop es pop bx pop ax retf ; back to dos intr endp ;------------------------------------------------------ ; Storage space for the addresses of free umb blocks umb struc start dw ? len dw ? umb ends ;you can add to the following list, as long as the last one is 0,0 free umb <0D000h, 1FFFh> ;my only block (at d000, length 1fff) umb <0, 0> ;space for extra block umb <0, 0> ;and another block umb <0, 0> ;The end of the blocks is marked ; with 0,0 DON'T REMOVE THIS!!!!! ;------------------------------------------------------ ; This is the code for the actual UMB memory provider umbreq proc near push ds push si push cx push bx push cs pop ds mov si, offset free xor cx, cx ;clear dx and use it to compare xchg dx, cx ;to largest found as yet - cx=size search: lodsw ;read startsegment into ax or ax, ax ;is it 0 jz fini ; then buzz off mov bx, ax ; otherwise store into bx lodsw ;read length in ax cmp bx, 0FFFFh ;is startsegm=ffff=given away je search ; yes: then find next block cmp dx, ax ; no: larger than largest upto now? jae szchk ; no: check size mov dx, ax ; yes: mark as largest szchk: cmp cx, ax ;will it fit? ja search ; no: search next ; YEAH! Found a block mov [si-4], 0FFFFh ; mark as used mov dx, ax ; put blocksize in dx mov ax, 1 ;say Succes pop cx ;still had bx on stack jmp short return fini: xor ax, ax ;no fitting UMB or dx, dx ;is dx=0?, so largest found=0 jnz sizerr ; if not: problem with size pop bx ; if yes: BH should stay intact mov bl, 0B1h ; and BL signals: out of UMBs jmp short return sizerr: pop bx ;BH remains intact mov bl, 0B0h ;BL signals: there are smaller ones return: pop cx pop si pop ds popf retf umbreq endp ;------------------------------------------------------ ; Storage space for old XMS-handler. The first byte stores WHETHER there ; was an XMS handler already (that didn't provide UMB services). ; The next two words specify its location. isoldx db 00h oldxms label word dw ?,? ;------------------------------------------------------ ; This is the small XMS manager that we install. It will only react ; to requests for UMBs (so when AH=10h). If not, it *should* pass ; control to the existing XMS manager - provided there is one. Or ; otherwise inform the caller that there is no eXt memory. assume es:nothing, ds:nothing umbctrlr: jmp short hookch ;MUST be a *short* jmp nop ; The nops are there because nop ; a himem handler always start nop ; with 5 special bytes. hookch: pushf cmp ah, 10h ;is it a UMB request? je umbreq ; yes: execute it cmp [isoldx], 0h ; no: is there an XMS-handler? jz Xreq1 ; no: give response like it popf ; yes: jump to old handler jmp dword ptr cs:[oldxms] ; Below is the code that will respond to non-UMB (and thus XMS-) ; requests when no XMS-manager is present. To nearly all requests ; (there are 11h) it will answer with AX=0000, meaning failure ; and BL=80, which gives the errormessage: not implemented. ; Only fns 00h and 08h are treated specially (as well as fn 10h, but ; that has been filtered out above - it's the UMB-request). Xreq1: cmp ah, 0h ;req 00h = get XMS version jnz Xreq2 mov bx, 0h ; ->internal revision nr=0 mov dx, 0h ; ->HMA not present jmp short byebye Xreq2: cmp ah, 08h ;req 08h = query extended mem jnz Xreq3 mov dx, 0h ; ->0k extended memory Xreq3: mov bl, 80h ; ->error: not implemented byebye: mov ax, 00h ; ->failure (always the case) popf retf ;------------------------------------------------------ ; Storage space for old interrupt vector 2f old2f label word dw ?,? ;------------------------------------------------------- ; This is the code that is chained to the front of interrupt 2f. ; It will handle requests nrs. 4300 and 4310, and leave all others ; to the existing code. handl: pushf cmp ah, 43h ;is request for HIMEM? jne not4me ; no: pass on cmp al, 10h ; is request: where is handler? jne mustbe ; if not, then must be al=00 mov bx, offset umbctrlr ; put handler's ofs in bx push cs ; and its segment pop es ; in es jmp short getout mustbe: mov al, 80h ;al <>10 so must be 00, so request ;is: is there handler? Yes => 80h getout: popf iret not4me: popf ;request wasn't for me jmp dword ptr cs:[old2f] ;so give back to old handl ;================================================================= ; ; NON-RESIDENT PART ; ; The part that follows now will not remain resident. It will be ; executed only once: at the time the driver is installed by ; DOS' bootprocedures. ; ; This code takes care of (1) hooking our intercepting code to ; int 2f, (2) hooking our small XMS-manager to the already installed ; one - provided there is one, (3) and if not, installing the ; the response-robot that will inform callers that there's no eXt ; memory. ; ;------------------------------------------------------- ; Installation routine. Called once. assume ds:zwetsUMB, es:rh inst: push cx ;save em push dx push ds push cs ;and set ds to cs pop ds mov ah, 09h mov dx, offset hello1$ ;say welcome int 21h mov dx, offset empty$ int 21h mov dx, offset hello2$ int 21h mov dx, offset empty$ int 21h mov dx, offset hello3$ int 21h mov dx, offset hello4$ int 21h mov dx, offset empty$ int 21h mov dx, offset autho1$ int 21h mov dx, offset autho2$ int 21h mov dx, offset empty$ int 21h mov ax, 4300h ;check if there is an XMShandler int 2Fh ;already cmp al, 080h ;is it there? jne SetVec ; no: go further mov [isoldx],01h ;signal yourself there is one mov ax, 4310h ;get its address int 2Fh mov [oldxms], bx ;and store it mov [oldxms+2], es mov ah, 09h ;tell user mov dx, offset found$ int 21h mov dx, offset empty$ int 21h mov ah, 10h ;check if it services UMBs by mov dx, 0FFFFh ;trying to allocate FAR TOO much call dword ptr [oldxms] cmp bl, 80h ;error: not implemented? jz SetVec ; then good - continue mov ah, 09h ;otherwise: get off, mov dx, offset oops$ ;you're not needed. int 21h les bx, dword ptr [hdrptr] xor ax,ax mov es:[bx].rh0_brk_ofs, ax jmp short dexit SetVec: mov ax, 352Fh ; get vector 2f int 21h mov [old2f], bx ;and store it mov [old2f]+2, es mov ax, 252Fh ;set it to our own mov dx, offset handl int 21h mov ah, 09h mov dx, offset instok$ ;say we did it int 21h mov ax, offset inst ;upto inst it should stay les bx, dword ptr [hdrptr] ; resident, which we tell mov es:[bx].rh0_brk_ofs, ax ; dos via the rqhdr. xor ax,ax ;0 no errors dexit: pop ds pop dx pop cx jmp exit hello1$ db 0Dh,0Ah,'╒══════════════╡ Use!UMBs ╞═════════════╕',0Dh,0Ah,'$' empty$ db '│ │',0Dh,0Ah,'$' hello2$ db '│ Upper Memory Block - Manager │',0Dh,0Ah,'$' hello3$ db '│ Works on any PC/XT/AT, either with or │',0Dh,0Ah,'$' hello4$ db '│ without Extended or Expanded Memory! │',0Dh,0Ah,'$' found$ db '│ * found extended memory manager * │',0Dh,0Ah,'$' autho1$ db '│ Author: Marco van Zwetselaar │',0Dh,0Ah,'$' autho2$ db "│ dedicated it to the Public Domain 1991 │",0Dh,0Ah,'$' instok$ db '╘══╡ Version 2.0 ╞══════════╡ Installed! ╞══╛',0Dh,0Ah,0Ah,'$' oops$ db '╘═╡ Not Installed! UMBs Managed Already! ╞═╛',0Dh,0Ah,0Ah,'$' zwetsUMB ends end