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Assembly Source File | 1991-10-15 | 22.7 KB | 647 lines

;WATCH.ASM ;resident routine watches programs going resident ;and keeps a list of interrupt vector changes in an internal data structure ;============================================================================== ; written for TASM ; Copyright (c) 1986,1991 Kim Kokkonen, TurboPower Software. ; May be freely distributed but not sold except by permission. ; telephone: 719-260-6641, Compuserve 76004,2611 ;============================================================================== ; VERSION 2.2 3/4/87 ; First release, version to be consistent with MAPMEM.PAS ; : ; long intervening history ; : ; VERSION 3.0 9/24/91 ; add tracking for TSRs that unload themselves ; add support for TSRs loaded high ; WATCH may be loaded high ;============================================================================== ; Cseg segment public para assume cs:Cseg, ds:nothing, es:nothing, ss:nothing org 080H cmdline label byte ;pointer to command line org 100H comentry: jmp init ;put the following in WATCH.MAP to update MEMU.PAS public bmesg,changevectors,origvectors,currvectors,nextchange ;the following are useful when debugging ;public newint16,setup,shutdown,pspmatch,pspremove,dealloc ;public checkvec,vechdr,wrchg,cmpvec,savevec ;public stb21,stb27,st21idx,st27idx ;****************************************************************************** ;resident data structures not part of COM file changevectors = offset bmesg ;data area overwrites bmesg & beyond vrecsize equ 8 ;number of bytes per vector change record maxchanges equ 128 ;maximum number of vector changes vsize equ maxchanges*vrecsize ;size of vector change area in bytes ;vector table buffers origvectors equ offset changevectors+vsize ;location of original vector table veclen equ 400H ;size of vector table in bytes currvectors equ origvectors+veclen ;location of current vector table newstackpos equ currvectors+veclen ;location of newstack ssize equ 0080H ;number of bytes in temporary stack newloc equ newstackpos+ssize ;location for relocated installation code ;****************************************************************************** ;data structures part of COM file even nextchange dw 0 ;next position to write in data area ourcs dw ? ;value of cs at runtime ;temporary stack used by interrupt handler newss dw ? ;segment of our temporary stack newsp dw ? ;initial stack pointer tmpret dw ? ;used while switching stacks ;information saved about the calling program oldss dw ? ;stack segment oldsp dw ? ;stack pointer ;previous interrupt handlers kbd_int label dword old16 dw 2 dup (?) ;old int16 vector dos_int label dword old21 dw 2 dup (?) ;old int21 vector ;int16H function call for id check getid equ 'wa' ;function code for int16 chkid equ 'WA' ;returned by int16 getid check ;id code for a PSP data block pspid equ 0FFFFH ;id used to indicate a PSP block ;*********************************************************************** ;interrupt handler for int16 ;used only to avoid reinstallation newint16 proc near assume ds:nothing pushf ;save application flags sti cmp ax,getid ;see if our id function jne ex16 ;no, pass on to previous int16 mov ax,chkid ;return id code popf iret ;back to caller ex16: popf jmp kbd_int ;transfer control to the previous int16 newint16 endp ;*********************************************************************** ;int 21 handling stubs ;code counts on exact byte sequence of each stub st21siz equ 8 ;number of bytes in int 21 stub st21max equ 32 ;maximum times we can grab int 21 st21idx dw offset stb21 ;offset of current stub in use st21lim dw offset stb21+st21siz*(st21max-1) ;last usable stub stb21 label byte REPT st21max assume ds:nothing call int21work db 0EAh,0,0,0,0 ;jmp far immediate ENDM ;*********************************************************************** ;int 27 handling stubs ;code counts on exact byte sequence of each stub st27siz equ 8 ;number of bytes in int 27 stub st27max equ 32 ;maximum times we can grab int 27 st27idx dw offset stb27 ;offset of current stub in use st27lim dw offset stb27+st27siz*(st27max-1) ;last usable stub stb27 label byte REPT st27max assume ds:nothing call int27work db 0EAh,0,0,0,0 ;jmp far immediate ENDM ;*********************************************************************** ;put the interrupt address in es:bx into stub at di setstb proc near mov cs:[di+4],bx mov cs:[di+6],es ret setstb endp ;*********************************************************************** ;clear the call to int2?work in stub at di clrstb proc near mov word ptr cs:[di],9090H mov byte ptr cs:[di+2],90H ret clrstb endp ;*********************************************************************** ;do the real work of our int21 handler ;(control transferred from int 21 stub) ;note: if we run out of stub space, WATCH effectively disables itself int21work proc near assume ds:nothing pushf ;save flags ;check to see whether another program has grabbed int 21 or 27 push ax push es xor ax,ax mov es,ax mov ax,ourcs cmp es:[4*21H+2],ax ;do we own int 21? jnz grab ;if not, grab it back cmp es:[4*27H+2],ax ;do we own int 27? jz haveem ;we're done if so ;we need to grab at least one interrupt grab: push bx push dx push di push ds push cs pop ds assume ds:cseg mov ax,es:[4*21H+2] ;get current int 21 segment cmp ax,ourcs ;do we own int 21? je have21 ;jump if so mov bx,es:[4*21H] ;get current int 21 offset mov es,ax ;es:bx = current int 21 mov di,st21idx call clrstb ;turn existing stub into straight jump cmp di,st21lim ;room for more stubs? jae have21 ;forget it if no more room add di,st21siz ;move to next stub mov st21idx,di call setstb ;have next stub jump to current int 21 mov dx,di mov ax,2521H pushf call dos_int have21: xor ax,ax mov es,ax mov ax,es:[4*27H+2] ;get current int 27 segment cmp ax,ourcs ;do we own int 27? je have27 ;jump if so mov bx,es:[4*27H] ;get current int 27 offset mov es,ax ;es:bx = current int 27 mov di,st27idx call clrstb ;turn existing stub into straight jump cmp di,st27lim ;room for more stubs? jae have27 ;forget it if no more room add di,st27siz ;move to next stub mov st27idx,di call setstb ;have next stub jump to current int 27 mov dx,di mov ax,2527H pushf call dos_int have27: pop ds assume ds:nothing pop di pop dx pop bx haveem: pop es pop ax ;trap DOS functions 31 and 49 cmp ah,31H ;terminate and stay resident call? jne chk49 call checkvec ;call routine to handle stayres calls jmp short ex21 chk49: cmp ah,49H ;deallocate memory call? jne ex21 call dealloc ;call routine to handle program unloading ex21: popf ret int21work endp ;*********************************************************************** ;do the real work of our int27 handler ;(control transferred from int 27 stub) int27work proc near assume ds:nothing pushf push dx add dx,15 ;pass size of block in paras to checkvec shr dx,1 shr dx,1 shr dx,1 shr dx,1 call checkvec pop dx popf ret int27work endp ;*********************************************************************** ;procedure dealloc ; checks whether deallocated memory is a PSP we're tracking ; if so, deletes that PSP block from our change table ; stores a new vector buffer dealloc proc near assume ds:nothing call setup mov bx,es ;save segment being deallocated in bx call pspmatch ;return si=0 if bx not a psp in changetable cmp si,0 je dedone call pspremove ;remove found psp from changetable mov di,currvectors ;save the new version of the vector table call savevec dedone: call shutdown ret dealloc endp ;*********************************************************************** ;procedure checkvec ; compares vectors to previous installation ; stores a new vector buffer ; on entry dx=paras to keep ; on exit dx=top segment going resident checkvec proc near assume ds:nothing call setup mov ah,51H ;get current PSP in bx pushf call dos_int add dx,bx ;dx = segment beyond that going resident call vechdr ;store the PSP segment of the program going resident call cmpvec ;scan the vector table looking for changes from our buffer mov di,currvectors ;save the new version of the vector table call savevec call shutdown ret checkvec endp ;*********************************************************************** ;setup routine for checkvec and dealloc ; switches stacks ; saves registers ; sets ds=cs setup proc near pop cs:tmpret ;save return address as we switch stacks mov oldss,ss ;save current stack mov oldsp,sp cli ;switch to our stack mov ss,newss mov sp,newsp sti push ax ;store registers push bx push cx push dx push si push di push ds push es mov ax,cs mov ds,ax ;ds = cs push cs:tmpret ret setup endp ;*********************************************************************** ;shutdown routine for checkvec and dealloc ; saves current vector image ; restores registers ; switches stacks shutdown proc near pop cs:tmpret pop es ;restore registers pop ds pop di pop si pop dx pop cx pop bx pop ax cli ;restore stack mov ss,cs:oldss mov sp,cs:oldsp sti push cs:tmpret ret shutdown endp ;*********************************************************************** ;procedure pspmatch ; returns si pointing to start of psp rec if bx is found, else si=0 ; entry: bx=PSP to match pspmatch proc near assume ds:cseg mov si,offset changevectors ;index into changevectors array mov dx,si add dx,nextchange ;dx = next available spot in changevectors matloop:cmp si,dx ;end of table? jae matdone cmp word ptr [si],pspid ;psp indicator? jnz matnext cmp [si+2],bx ;matching psp? jnz matnext ret ;return matching si matnext:add si,vrecsize jmp matloop matdone:xor si,si ;return si=0 ret pspmatch endp ;*********************************************************************** ;procedure pspremove ;removes psp started at index si pspremove proc near assume ds:cseg mov di,si ;save destination add si,vrecsize ;move to next record mov dx,offset changevectors add dx,nextchange ;dx = address of next available remloop:cmp si,dx ;end of table? jae remend cmp word ptr [si],pspid ;psp indicator? je remend add si,vrecsize jmp remloop remend: mov cx,dx sub cx,si ;cx = bytes to move shr cx,1 ;cx = words to move push ds pop es ;assure es=ds=cs cld rep movsw sub si,di ;update nextchange sub nextchange,si ret pspremove endp ;************************************************************************** ;procedure vechdr ; writes a header to the vector data area for this new TSR ; on entry bx has PSP of the new TSR, dx has top segment of TSR ; trashes di vechdr proc near assume ds:cseg cmp nextchange,vsize-vrecsize ;assure room for next record ja vecex ;ignore if no room mov di,nextchange ;index into changevectors array mov word ptr [di+changevectors],pspid ;store id word mov word ptr [di+changevectors+2],bx ;store PSP value ;two words in record left unitialized add nextchange,vrecsize ;move to next data element vecex: ret vechdr endp ;************************************************************************** ;procedure wrchg ; writes information about changed vectors to the data area ; on entry: ; cx has changed vector number ; ax:bp contains vector value ; on exit: ; flags changed wrchg proc near assume ds:nothing cmp nextchange,vsize-vrecsize ;assure room for next record ja wrcex push di mov di,offset changevectors add di,nextchange ;index into changevectors array mov cs:[di],cx ;store interrupt vector number mov cs:[di+2],bp ;store vector offset mov cs:[di+4],ax ;store segment ;one word in record left unused add nextchange,vrecsize ;move to next data element pop di wrcex: ret wrchg endp ;************************************************************************** ;procedure cmpvec ; compares vectors in buffer to those in use ; writes numbers of those different to data area ; doesn't write those that point outside of the TSR ; on entry: ; bx has base of TSR, dx has top of TSR ; on exit: ; ax,cx,si,di destroyed ; flags changed cmpvec proc near assume ds:nothing push bp push ds push es xor si,si ;source offset 0 mov ds,si ;source address segment 0 mov ax,cs mov es,ax xor cx,cx ;vector counter mov di,currvectors ;destination offset cld ;upward direction nexvec: cmpsw ;compare offsets je cmpseg ;compare segments if offsets equal cmpsw ;compare next word, ignore result jmp short cmprng ;make sure vector points into program cmpseg: cmpsw ;compare segments je vecinc ;jump if equal cmprng: mov bp,ds:[si-4] ;save vector offset in bp mov ax,ds:[si-2] ;save vector segment in ax cmp ax,bx ;lower than base of TSR? jb cmp21 ;jump if so cmprng2:cmp ax,dx ;above top of TSR? jae cmp21 ;jump if so call wrchg ;write changed vector jmp short vecinc cmp21: cmp cl,21H ;checking int 21? jne vecinc ;jump if not cmp ax,ourcs ;does int21 point to us? jne vecinc ;jump if not push di mov di,st21idx mov bp,cs:[di+4] ;save current offset in bp mov ax,cs:[di+6] ;save current segment in ax pop di cmp ax,bx ;lower than base of TSR? jb vecinc ;jump if so cmp ax,dx ;above top of TSR? jae vecinc ;jump if so call wrchg ;write changed vector vecinc: inc cx ;next vector number cmp cx,00FFH jbe nexvec ;continue until 256 vectors checked pop es pop ds pop bp ret cmpvec endp ;************************************************************************** ;procedure savevec ; saves image of interrupt vectors ; on entry: ; di has destination offset ; on exit: ; ax,cx,si,di destroyed ; flags changed savevec proc near assume ds:nothing push ds push es xor si,si ;offset 0 mov ds,si ;source address segment 0 mov ax,cs mov es,ax ;destination always in this code segment mov cx,200H ;512 integers to store cld ;copy up rep movsw ;copy vectors to our table pop es pop ds ret savevec endp ;of proc savevec ;************************************************************************** ;resident portion above, temporary portion below ;************************************************************************** align 16 bmesg db 'Cannot install WATCH more than once....',13,10,36 mesg db 'WATCH 3.0, Copyright 1991 TurboPower Software',13,10 mesg2 db 'Installed successfully',13,10,36 pname db 'TSR WATCHER' plen equ $-pname ;length of string ;************************************************************************** init proc near assume ds:cseg ;use int 16h test to check for previous installation mov ax,getid ;int16h diagnostic request int 16h ;now, ax=chkid if installed cmp ax,chkid ;TSR already installed? jne success ;no - jump if not installed ;error exit mov dx,offset bmesg ;error message mov ah,09H int 21H ;DOS print string mov ax,4C01H ;exit with error int 21H ;print a success message success: mov dx,offset mesg ;start of message to write mov ah,09H int 21H ;DOS print string ;relocate ourselves out of the way of the vector tables mov ax,cs mov es,ax mov di,newloc+10H push di ;will act as a return address mov si,offset newstk mov cx,lastcode-newstk rep movsb ;move code ret ;"return" to the relocated code ;initialize location of WATCH stack newstk: mov newsp,newstackpos+ssize mov newss,cs ;stack seg is code seg ;get int 16H vector mov ax,3516H ;GetVector DOS function call int 21H mov old16,bx ;store first word of old21 mov old16[2],es ;store second word ;get int 27H vector mov ax,3527H ;GetVector DOS function call int 21H mov ax,offset setstb mov di,st27idx call ax ;save vector in first stub ;get int 21H vector mov ax,3521H ;GetVector DOS function call int 21H mov old21,bx ;store first word of old21 (offset) mov old21[2],es ;store second word (segment) mov ax,offset setstb mov di,st21idx call ax ;save vector in first stub ;put an id label at offset 80H to allow other programs to recognize WATCH mov ax,cs mov es,ax mov cx,plen ;length of name string mov si,offset pname ;offset of name string mov di,offset cmdline ;offset of DOS command line cld ;transfer in forward direction mov al,cl stosb ;store length byte first rep movsb ;transfer characters ;store image of original vector table (overwrites messages) mov di,origvectors mov ax,offset savevec call ax ;absolute call works as code is moved ;store it again into the current vector table mov di,currvectors mov ax,offset savevec call ax ;absolute call works as code is moved ;install the new vectors mov ax,2516H mov dx,offset newint16 int 21H mov ax,2527H mov dx,offset stb27 int 21H mov ax,2521H mov dx,offset stb21 int 21H ;save cs in a convenient place mov ourcs,cs ;terminate and stay resident mov dx,newloc add dx,000FH mov cl,4 shr dx,cl mov ax,3100H ;return success code pushf call dos_int ;don't log vectors WATCH itself takes over lastcode: init endp Cseg ends end ComEntry