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Assembly Source File | 1989-03-31 | 22.3 KB | 815 lines

page 60,126 ; Name ivctrl -- Return address of intervention control block. ; ; Synopsis pblock = ivctrl(); ; ; IV_CTRL far *pblock ; Address of intervention control block. ; ; Description This function returns the address of the intervention ; control block (IV_CTRL structure). This module also ; defines the structure and the intervention filters. ; ; Any program using intervention code contains a unique ; intervention control block to control the intervention ; filters that give control to the installed intervention ; function at the proper time. The block is located in ; the code segment of the filters, so in general it must ; be referenced via a far pointer. ; ; It is seldom necessary to access the intervention ; control block directly. IVINSTAL performs all ; operations necessary to install the intervention filter. ; However, if the intervention mechanism should fail, it ; may be useful to examine the following fields in the ; structure: ; ; key_event ; wait ; req ; awake ; timer_busy ; kb_busy ; com2_busy ; com1_busy ; disk_busy ; idle_busy ; idle_safe ; cbreak ; ; Returns *pblock Address of intervention control block. ; ; Version 6.00 (C)Copyright Blaise Computing Inc. 1987-1989 ; include beginasm.mac beginMod ivctrl ;********************************************************* ; ; Define symbols and macros ; Hot key action codes: IV_KY_NONE equ 0 ; No hot key or action. IV_KY_WAKE equ 3 ; Invoke intervention function and ; awaken it if asleep. BEGIN_IV_FILTER macro ;; BEGIN_IV_FILTER: Macro local begin_label ;; to build pointer to ;; the IV_CTRL structure jmp short begin_label ;; at the beginning of each ;; filter. dw offset begin_block begin_label: endm IV_VECTORS struc ; IV_VECTORS: set of interrupt vectors ; used by intervention code. ; (Must match version in BINTERV.H exactly!) ptimer dd 0 ; INT 08h: Timer tick. pkeybd dd 0 ; INT 09h: Keystroke. pdisk dd 0 ; INT 13h: BIOS disk services. pdos dd 0 ; INT 21h: DOS functions. pidle dd 0 ; INT 28h: DOS idle. ; pcom1 dd 0 ; INT 0ch: First asynchronous communication ; port. pcom2 dd 0 ; INT 0bh: Second asynchronous communication ; port. IV_VECTORS ends ;********************************************************* ; ; Allocate and initialize the IV_CTRL structure. beginCseg ivctrl ;Note: the following sequence of thirty variables must exactly ; match the IV_CTRL structure as defined in BINTERV.H. begin_block equ $ signature dw 0 ; Signature identifying this structure. sign2 dw 0 ; One's complement of "signature". ident db 16 dup (0) ; Identifying name. psp dw 0 ; PSP of this program. enabled dw 0 ; Nonzero if enabled (this prevents the ; filters from being installed twice). pgate dd 0 ; Gateway for invoking this program ; from outside. prev_vec IV_VECTORS <> ; Previous values of interrupt vectors. ; dos_need db 0 ; Nonzero if intervention function ; uses DOS services. dkey_need db 0 ; Nonzero if intervention function ; uses DOS functions 1-12. ; pkeytab dd 0 ; Table of hot keys. ktsize dw 0 ; Size of hot key table. ; keyfound dw 0 ; Found key, if any. keyaction dw IV_KY_NONE ; ; ; Internal state of filters: ; iv_wait db 0 ; Nonzero if INT 21h or INT 28h filter ; is cycling, waiting for the ; intervention function to be invoked. req db 0 ; Nonzero if intervention function ; needs invocation. awake db 0 ; Zero if intervention function is ; asleep. ; ; Busy flags: timer_busy db 0 ; INT 08h filter. kb_busy db 0 ; INT 09h filter. com2_busy db 0 ; INT 0bh filter. com1_busy db 0 ; INT 0ch filter. disk_busy db 0 ; INT 13h filter. idle_busy db 0 ; INT 28h filter. ; idle_safe db 0 ; Nonzero if INT 28h is in progress ; and DOS functions are available ; (but not functions 1-12). ; pschedblk dd 0 ; Entry point into scheduler's ISR ; control block. ; pdos_crit dd 0 ; Address of DOS critical section flag ; (busy flag). ; prev_16h_vec dd 0 ; Address of previous INT 16h handler ; (if replaced). cbreak db 0 ; Nonzero if Ctrl-C or Ctrl-Break ; detected during this invocation of ; the intervention function. no_call db 0 ; Nonzero if user wants to prevent ; invocation of intervention function. filter_mask dw 0 ; Map of installed filters. kb_ext db 0 ; Nonzero if extended BIOS keyboard ; services to be used. ; _res0 db 0 ; Reserved for future use. ; _reserved db 8 dup (0) ; Reserved for future use. ; End of IV_CTRL structure. ;********************************************************* ; ; Internal variables timer_caller_offset dw ? ; Return address for INT 08h. timer_caller_seg dw ? kb_caller_offset dw ? ; Return address for INT 09h. kb_caller_seg dw ? com2_caller_offset dw ? ; Return address for INT 0bh. com2_caller_seg dw ? com1_caller_offset dw ? ; Return address for INT 0ch. com1_caller_seg dw ? disk_caller_offset dw ? ; Return address for INT 13h. disk_caller_seg dw ? key_caller_offset dw ? ; Return address for INT 16h. key_caller_seg dw ? key_caller_flags dw ? ; Flags pushed by caller on stack. key_entry_flags dw ? ; Flags on entry to IVBIOSKY. key_func_number db ? ; AH value on entry to INT 16h. key_busy db 0 ; Busy flag for INT 16h filter. dos_caller_offset dw ? ; Return address for INT 21h. dos_caller_seg dw ? dos_save_flags dw ? ; Flags pushed by INT 21h caller. idle_caller_offset dw ? ; Return address for INT 28h. idle_caller_seg dw ? ;********************************************************* ; ; Begin code for IVCTRL function. beginProc ivctrl assume ds:nothing, es:nothing, ss:nothing mov dx,cs ; Load address of intervention mov ax,offset begin_block ; control block into DX:AX. ret endProc ivctrl ;********************************************************* ; ; IVTIMER -- INT 8 filter ; ; This function calls the scheduler on every clock tick, ; except that it never does so in a nested fashion, ; so it is reentrant. beginProc ivtimer ; (IVTIMER will perform a far return.) assume ds:nothing, es:nothing, ss:nothing BEGIN_IV_FILTER pushf cli ; Disable interrupts until we can ; set the busy flag. cmp timer_busy,0 ; If this filter is already active, jne timer_jmp_prev ; If timer busy, jump to previous ; handler. cmp no_call,0 ; If no calls wanted, jump to jne timer_jmp_prev ; previous handler. cmp com1_busy,0 ; If COM1 busy, jne timer_jmp_prev ; jump to previous handler. cmp com2_busy,0 ; If COM2 busy, jne timer_jmp_prev ; jump to previous handler. cmp dos_need,0 ; If DOS is not needed je timer_enter cmp disk_busy,0 ; or disk is idle, je timer_enter ; go call scheduler. ; Else jump to previous handler. timer_jmp_prev: popff jmp prev_vec.ptimer ; Jump to previous handler. ; The previous handler will return ; directly to the original caller. timer_enter: mov timer_busy,1 ; Prevent nesting. popff pop timer_caller_offset ; Save caller's address. pop timer_caller_seg call prev_vec.ptimer ; Call previous handler, which will ; pop the flags from the top of ; the stack, send the EOI to the ; interrupt controller, and ; reenable interrupts. pushf ; Call scheduler. call pschedblk push timer_caller_seg push timer_caller_offset mov timer_busy,0 ; No longer any need to protect ; stored copy of caller's address. db 0cbh ; Far return. endProc ivtimer ;********************************************************* ; ; IVKEYBD -- INT 9 filter ; ; This filter checks the most recent keystroke to see if it ; is a hot key. If so, it records the keystroke and ; removes it from the type-ahead buffer. beginProc ivkeybd assume ds:nothing, es:nothing, ss:nothing BEGIN_IV_FILTER pushf cli ; Disable interrupts until we can ; set the busy flag. cmp kb_busy,0 ; If this filter is already active, je kb_enter popff jmp prev_vec.pkeybd ; jump to previous handler. ; The previous handler will return ; directly to the original caller. kb_enter: mov kb_busy,1 ; Prevent nesting. popff pop kb_caller_offset ; Save caller's address. pop kb_caller_seg call prev_vec.pkeybd ; Call previous handler, which will ; pop the flags from the top of ; the stack, send the EOI to the ; interrupt controller, and ; reenable interrupts. pushf push ax push bx push cx push dx push bp push si push di push ds push es cmp keyaction,IV_KY_NONE jne kb_exit ; Quit if any hot key has already ; been detected. ; Scan table of hot keys: mov cx,ktsize ; jcxz kb_exit ; Quit if table is empty. cmp kb_ext,0 ; Prepare to call BIOS: mov dh,10h ; DH = 10h if extended services, jne kb_chosen mov dh,0 ; DH = 0 if normal BIOS services. kb_chosen: mov ah,1 ; Examine most recent keystroke. add ah,dh int 16h jz kb_exit ; Quit if none recorded. ; AX contains char & key code. les di,pkeytab cld kb_loop: scasw ; Check one hot key listing. je kb_found inc di ; Step over its action code. inc di loop kb_loop mov keyfound,0 ; Most recent keystroke is not ; a hot key. mov keyaction,IV_KY_NONE jmp short kb_exit kb_found: ; Found a hot key. mov bx,es:[di] ; Get key action for found key. cmp awake,0 jne kb_awake ; If intervention function is asleep cmp bx,IV_KY_WAKE ; and this is not the wakeup key, jnz kb_exit ; then quit. kb_awake: mov keyfound,ax ; Record hot key for access by the mov keyaction,bx ; scheduler. mov ah,0 ; Drop the keystroke from the add ah,dh int 16h ; type-ahead buffer. kb_exit: pop es pop ds pop di pop si pop bp pop dx pop cx pop bx pop ax ; Top of stack contains flags returned ; by previous INT 9 handler. push kb_caller_seg push kb_caller_offset mov kb_busy,0 iret endProc ivkeybd ;********************************************************* ; ; IVCOM2 -- INT 0bh filter (hardware events on communications port 2) ; ; The sole purpose for this filter is to maintain the com2_busy ; flag telling the scheduler when comm port 2 interrupts are in ; progress. beginProc ivcom2 ; (IVCOM2 will perform a far return.) assume ds:nothing, es:nothing, ss:nothing BEGIN_IV_FILTER pushf cli ; Disable interrupts until we can ; set the busy flag. cmp com2_busy,0 ; If this filter is already active, je com2_enter popff jmp prev_vec.pcom2 ; jump to previous handler. ; The previous handler will return ; directly to the original caller. com2_enter: mov com2_busy,1 ; Prevent nesting. popff pop com2_caller_offset ; Save caller's address. pop com2_caller_seg call prev_vec.pcom2 ; Call previous handler, which will ; pop the flags from the top of ; the stack. push com2_caller_seg push com2_caller_offset mov com2_busy,0 db 0cbh ; Far return. endProc ivcom2 ;********************************************************* ; ; IVCOM1 -- INT 0ch filter (hardware events on communications port 1) ; ; The sole purpose for this filter is to maintain the com1_busy ; flag telling the scheduler when comm port 1 interrupts are in ; progress. beginProc ivcom1 ; (IVCOM1 will perform a far return.) assume ds:nothing, es:nothing, ss:nothing BEGIN_IV_FILTER pushf cli ; Disable interrupts until we can ; set the busy flag. cmp com1_busy,0 ; If this filter is already active, je com1_enter popff jmp prev_vec.pcom1 ; jump to previous handler. ; The previous handler will return ; directly to the original caller. com1_enter: mov com1_busy,1 ; Prevent nesting. popff pop com1_caller_offset ; Save caller's address. pop com1_caller_seg call prev_vec.pcom1 ; Call previous handler, which will ; pop the flags from the top of ; the stack. push com1_caller_seg push com1_caller_offset mov com1_busy,0 db 0cbh ; Far return. endProc ivcom1 ;********************************************************* ; ; IVDISK -- INT 13h filter (BIOS disk services) ; ; The sole purpose for this filter is to maintain the disk_busy ; flag telling the scheduler when BIOS disk operations are in ; progress. beginProc ivdisk ; (IVDISK will perform a far return.) assume ds:nothing, es:nothing, ss:nothing BEGIN_IV_FILTER pushf cli ; Disable interrupts until we can ; set the busy flag. cmp disk_busy,0 ; If this filter is already active, je disk_enter popff jmp prev_vec.pdisk ; jump to previous handler. ; The previous handler will return ; directly to the original caller. disk_enter: mov disk_busy,1 ; Prevent nesting. popff pop disk_caller_offset ; Save caller's address. pop disk_caller_seg call prev_vec.pdisk ; Call previous handler, which will ; pop the flags from the top of ; the stack. push disk_caller_seg push disk_caller_offset mov disk_busy,0 db 0cbh ; Far return. endProc ivdisk ;********************************************************* ; ; IVBIOSKY -- INT 16h filter (BIOS keyboard services) ; ; This filter prevents DOS from encountering a Ctrl-C ; from the keyboard. It works by filtering all calls to ; keyboard functions 0 (wait for keystroke) and 1 (test for ; keystroke). If a Ctrl-C is encountered, the keystroke ; is discarded and the operation is repeated. beginProc ivbiosky assume ds:nothing, es:nothing, ss:nothing pushf cli ; Disable interrupts until we can ; set the busy flag. cmp ah,2 ; Filter only if function number jae key_jmp_prev ; is 0 or 1. cmp key_busy,0 ; If this filter is already active, je key_enter ; jump to previous handler. key_jmp_prev: popff jmp prev_16h_vec ; The previous handler will return ; directly to the original caller. key_enter: mov key_busy,1 ; Prevent nesting. mov key_func_number,ah ; Save function number. popff pushf pop key_entry_flags pop key_caller_offset ; Save caller's address and flags pop key_caller_seg pop key_caller_flags push key_caller_flags ; but keep caller's flags on ; top of stack. key_try: call prev_16h_vec ; Call previous handler, which will ; pop the flags from the top of ; the stack. pushf ; Save flags as modified by ; previous handler. cmp key_func_number,0 jne key_ready ; This is function 0: await ; keystroke. cmp al,3 jne key_exit mov cbreak,1 ; Found a Ctrl-C. pop ax ; Discard flags from top of stack. key_retry: ; At this point, stack is empty ; of things that concern us. push key_entry_flags ; Reestablish the flags that were popff ; in effect at the beginning. push key_caller_flags mov ah,key_func_number jmp key_try key_ready: ; This is function 1: test for ; keystroke. ; Check ZF to see if char was found. popff pushf jz key_exit ; Exit if no character found. cmp al,3 jnz key_exit ; Exit if character found is not ; a Ctrl-C. mov cbreak,1 ; Found a Ctrl-C. pop ax ; Discard flags from top of stack. push key_entry_flags ; Reestablish the flags that were popff ; in effect at the beginning. push key_caller_flags mov ah,0 ; Consume the Ctrl-C. call prev_16h_vec jmp key_retry key_exit: ; Top of stack has flags returned ; by previous handler. push key_caller_seg push key_caller_offset mov key_busy,0 iret endProc ivbiosky ;********************************************************* ; ; IVCBREAK -- INT 1Bh handler ; ; This filter prevents DOS from encountering a Ctrl-Break. beginProc ivcbreak assume ds:nothing, es:nothing, ss:nothing mov cbreak,1 iret endProc ivcbreak ;********************************************************* ; ; IVDOS -- INT 21h filter ; ; The purpose of this filter is to delay the return from ; DOS calls if the intervention function needs DOS and is ; waiting for service. After invoking DOS, this filter may ; enter a wait loop that will soon be released by the ; scheduler (which is invoked by a clock tick). beginProc ivdos ; (IVDOS will perform a far return.) assume ds:nothing, es:nothing, ss:nothing BEGIN_IV_FILTER push bx xchg ax,bx ; Save AX in BX. lahf ; Save flags in AH. cmp dos_need,0 ; If intervention function doesn't je dos_jmp_prev ; need DOS, just invoke DOS directly. cmp timer_busy,0 ; If timer tick is busy, jne dos_jmp_prev ; just invoke DOS directly. ; Certain DOS functions examine their ; return address or do not return to ; their caller. We must invoke them ; directly: ; ; (Remember that we saved the function ; number in BH.) ; cmp bh,26h ; Function 26h: Make PSP je dos_jmp_prev ; (examines caller's address) ; cmp bh,4Bh ; Function 4Bh: Exec je dos_jmp_prev ; (can destroy registers on return) ; cmp bh,00h ; Function 00h: Terminate je dos_jmp_prev ; (does not return) ; cmp bh,31h ; Function 31h: Keep process je dos_jmp_prev ; (does not return) ; cmp bh,4ch ; Function 4ch: Terminate jne dos_enter ; (does not return) dos_jmp_prev: sahf ; Restore the flags. xchg ax,bx pop bx jmp prev_vec.pdos ; Jump to previous handler. ; The previous handler will return ; directly to the original caller. dos_enter: ; This is a normal DOS function call. sahf ; Restore the flags. xchg ax,bx pop bx cli ; Rearrange the top items on the pop dos_caller_offset ; stack to bring the flags to pop dos_caller_seg ; the top. pop dos_save_flags push dos_caller_seg push dos_caller_offset push dos_save_flags call prev_vec.pdos ; On return, DOS pops the flags from ; the top of the stack. pushf cli cmp req,0 ; Skip the wait loop if the intervention je dos_exit ; function doesn't require service ; at this time. push es ; Check the DOS critical section flag: push di les di,pdos_crit cmp es:byte ptr [di],0 pop di pop es jne dos_exit ; if DOS is busy, skip the wait loop ; so DOS can complete its business. mov iv_wait,1 sti dos_wait: ; Wait until somebody sets iv_wait cmp iv_wait,0 ; to zero. jne dos_wait dos_exit: ; Top of stack has flags returned by ; previous INT 21h handler. popff db 0cbh ; Far return. endProc ivdos ;********************************************************* ; ; IVIDLE -- INT 28h filter ; ; The purpose of this filter (similar to the INT 21h filter above) ; is to delay the return from INT 28h calls if the intervention ; function is waiting for service. After invoking the previous ; handler, this filter may enter a wait loop that will soon be ; released by the scheduler (which is invoked by a clock tick). beginProc ividle assume ds:nothing, es:nothing, ss:nothing BEGIN_IV_FILTER pushf cli ; Disable interrupts until we can ; set the busy flag. cmp idle_busy,0 ; If this filter is already active jne idle_jmp_prev cmp dos_need,0 ; or if DOS is not needed je idle_jmp_prev cmp dkey_need,0 ; or if DOS functions 1-12 are needed je idle_enter idle_jmp_prev: popff jmp prev_vec.pidle ; jump to previous handler. ; The previous handler will return ; directly to the original caller. idle_enter: mov idle_busy,1 ; Prevent nesting. popff pop idle_caller_offset ; Save caller's address. pop idle_caller_seg call prev_vec.pidle ; Call previous handler. On return, ; it pops the flags from the top ; of the stack. mov idle_safe,1 ; Now we're in the nice INT 28h ; environment: all DOS functions are ; allowable except functions 1-12. pushf cli cmp req,0 ; Skip the wait loop if the intervention je idle_exit ; function doesn't require service ; at this time. sti mov iv_wait,1 idle_wait: cmp iv_wait,0 ; Wait until somebody sets iv_wait jne idle_wait ; to zero. idle_exit: ; Top of stack contains flags returned ; by previous INT 28h handler. push idle_caller_seg push idle_caller_offset mov idle_safe,0 mov idle_busy,0 iret endProc ividle endCseg ivctrl endMod ivctrl end