PAGE 90,132 ;A2 TITLE GRTABHAN - INTERRUPT HANDLER FOR INT 2FH, GRAFTABL LOADED ;****************** START OF SPECIFICATIONS ***************************** ; MODULE NAME: GRTABHAN.SAL ; DESCRIPTIVE NAME: For GRAFTABL, this is the Multiplexor Interrupt Handler ;FUNCTION: This module contains the Interrupt Handler that will be hooked ; into the INT 2FH vector. When invoked with AL=0, it responds ; that GRAFTABL is loaded by changing AL to contain hex FF. If ; option AL=1 specified, it puts into the vector at DS:[BX] the ; pointer to the previously loaded table. ; NOTES: ; This module should be processed with the SALUT preprocessor: ; SALUT GRTABHAN ; To assemble these modules, the alphabetical or sequential ; ordering of segments may be used. ; For LINK instructions, refer to the PROLOG of the main module, ; GRTAB.SAL. This module, containing a resident interrupt handler, ; should be first in the list of .OBJ to be linked. ; At the time this handler code is made resident, the loader, GRTAB, ; made certain instruction modifications. PATCH_OFF and PATCH_SEG ; are the immediate word fields of two move word immediate to ; storage type of instructions. The loaded Revised these to ; contain the offset and the segid respectively of where the ; resident font table would be that is to stay resident. ; Also at load time, GRTAB made another instruction modification by ; changing the JUMP DUMMY instruction's DWORD immediate field to ; contain the vector pointing to the previous owner of the ; Multiplexor Interrupt Vector. ; ENTRY POINT: There are two entry points: one, from DOS at 100H, is ; END_PSP. The jump instruction there has nothing to do with ; the interrupt handler, but merely jumps to the GRTAB module to ; what is effectively the real DOS entry point, ENTRY_POINT. ; The other is where the interrupt vector will be set to point, ; the entry point to the interrupt handler code: HANDLER. ; For the rest of this module description, the HANDLER entry ; point conditions are being described. ; INPUT: AH = Multiplexor Number. I do nothing if this is not my own. ; The value of the Multiplexor Number is defined in the EQU: ; MY_MULTIPLEXOR_NUMBER as being the value, B0H. ; AL = Function Request. There are two functions recognized: ; 0 = "GET INSTALLED STATE" ; 1 = "WHERE ARE YOU?" ; and DS:BX points to vector to receive pointer ; to the previously installed GRAFTABL table. ; If Function request is not '1', it is assumed to be '0'. ; EXIT-NORMAL: If the proper multiplexor number is presented, respond with ; AH = 0FFH, otherwise, pass control to previous owner ; of this interrupt. ; EXIT-ERROR: None ; INTERNAL REFERENCES: ; ROUTINES: none ; DATA AREAS: ; PUBLIC symbols: ; PREV_OWN Far jump direct to previous owner of interrupt 2FH. ; PATCH_OFF Offset portion of vector pointing to loaded char cable. ; PATCH_SEG Segment portion of vector pointing to loaded char table. ; HANDLER Entry point pointed to by the vector at interrupt 2FH. ; HANDLER_SIZE Location of the end of the resident code portion of the ; interrupt 2FH handler, including the 60H bytes left of ; the PSP, so this offset is relative to the start of the PSP ; after the code has been relocated downward into the PSP. ; MPEXNUM The byte containing the value defined ; as being the id checked for when INT 2FH is called used ; to identify this GRAFTABL member of the multiplexor chain. ; ; EXTERNAL REFERENCES: ; ROUTINES: none ; DATA AREAS: none ;****************** END OF SPECIFICATIONS ***************************** IF1 %OUT COMPONENT=GRAFTABL, MODULE=GRTABHAN.SAL... ENDIF ; $SALUT (4,21,25,41) HEADER INCLUDE PATHMAC.INC ;AN006; HEADER MACRO TEXT .XLIST SUBTTL TEXT .LIST PAGE ENDM ; = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = VECTOR STRUC VECOFF DW ? ;OFFSET PORTION OF VECTOR POINTER VECSEG DW ? ;SEGMENT PORTION OF VECTOR POINTER VECTOR ENDS ; = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = ; DEFINITION OF FUNCTIONS TO BE REQUESTED OF INT 2FH GET_INST_STATE EQU 0 ;FUNCTION = "GET INSTALLED STATE" WHERE_R_U EQU 1 ;FUNCTION = "WHERE ARE YOU?" ; REQUESTS VECTOR OF LOADED TABLE BE ; PUT IN VECTOR POINTED TO BY DS:[BX] RES_FUNC EQU 0F8H ;RESERVED FUNCTIONS IN RANGE OF F8 TO FF, IGNORE ; OTHER EQUATES PATCHED EQU 0 ;DUMMY VALUE, TO BE REPLACED AT EXECUTION TIME INSTALLED EQU 0FFH ;RESPONSE, INDICATES THIS HANDLER IS INSTALLED MY_MULTIPLEX_NUMBER EQU 0B0H ;THE UNIQUE IDENTIFICATION NUMBER ASSIGNED ; TO "GRAFTABL" FOR INT 2FH ; = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = DUMMY_SEG SEGMENT AT 0 DUMMY LABEL FAR ;NOTHING HERE REALLY, ONLY ; USED TO MAKE MASM GENERATE A FAR CALL DIRECT ; THE ABSOLUTE VECTOR IN THAT INS WILL BE PATCHED DUMMY_SEG ENDS ; = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = HEADER CSEG SEGMENT PARA PUBLIC ;THIS SEGMENT IS ALIGNED ON PARA SINCE IT IS THE START OF THE LOAD MODULE, ; WHICH IS ON A PARA BOUNDARY ANYWAY. THIS MODULE IS PADDED AT THE END ; TO A MULTIPLE OF 16 BYTES, SO THE NEXT SEGMENT WILL ALSO START ; ON A PARA BOUNDARY, WHICH WILL BE THE US CHARACTER SET TABLE. ASSUME CS:CSEG EXTRN ENTRY_POINT:NEAR ORG 60H PUBLIC MOV_DEST MOV_DEST LABEL BYTE ;WHERE THIS INTERRUPT HANDLER ; WILL BE MOVED TO, FOLLOWED BY THE 1K TABLE. ORG 100H PUBLIC END_PSP ;BEGINNING HERE, THIS WILL BE MOVED TO "MOV_DEST" END_PSP EQU $ ;ENTRY POINT FROM DOS JMP ENTRY_POINT ;INIT THE INT HANDLER, SET UP CHAR TABLES ; THIS JUMP TARGET IS DEFINED ; IN THE GRTAB.SAL MODULE ; AREAS TO BE PATCHED WITHIN THIS MODULE PUBLIC PREV_OWN ;PATCH IS IN JMP INSTR TO PREVIOUS OWNER ;THE ABOVE PATCH IS FIXED BY THE GRTAB.SAL MODULE, JUST BEFORE ALTERING THE 2FH VECTOR PUBLIC PATCH_OFF ;OFFSET PORTION OF VECTOR POINTING TO LOADED CHAR TABLE PUBLIC PATCH_SEG ;SEGMENT PORTION OF VECTOR POINTING TO LOADED CHAR TABLE ;THE ABOVE TWO PATCHES ARE FIXED BY THE GRTAB.SAL MODULE, AT THE VERY BEGINNING. ;THIS NEXT ONE BYTE FIELD SHOULD BE KEPT AS THE BYTE JUST PREVIOUS TO THE ;INTERRUPT HANDLER ENTRY POINT AT "HANDLER". PUBLIC MPEXNUM MPEXNUM DB MY_MULTIPLEX_NUMBER ;PATCHING THIS ONE BYTE WILL CHANGE FOR ALL THE VALUE HEADER ;CONDITIONS OF REGS AT ENTRY TO HANDLER: ;INPUT: AH = MULTIPLEXOR NUMBER. I DO NOTHING IF THIS IS NOT MY OWN. ; AL = FUNCTION REQUEST. THERE ARE TWO FUNCTIONS RECOGNIZED: ; 0 = "GET INSTALLED STATE" ; 1 = "WHERE ARE YOU?" ; AND DS:BX POINTS TO VECTOR TO RECEIVE POINTER ; TO THE PREVIOUSLY INSTALLED GRAFTABL TABLE. ; IF FUNCTION REQUEST IS NOT '1', IT IS ASSUMED TO BE '0'. PUBLIC HANDLER HANDLER PROC FAR ;INTERRUPT HANDLER ENTRY POINT ; $SALUT (4,3,9,41) PATHLABL GRTABHAN ;AN006; CMP AH,MPEXNUM ;IS THIS MULTIPLEXOR REQUEST IS FOR ME? ; $IF E ;IF MY MULTIPLEX NUMBER IS CALLED JNE $$IF1 CMP AL,RES_FUNC ;IF IN RANGE F8-FF, DO NOTHING, JUST RETURN ; $IF B JNB $$IF2 CMP AL,WHERE_R_U ;IF REQUEST FOR "WHERE ARE YOU?" ; $IF E JNE $$IF3 ;FOR THIS REQUEST, DS:BX POINTS TO A VECTOR ; WHICH IS TO RECEIVE THE POINTER TO ; WHERE THE ORIGINAL TABLE WAS LOADED ;PASS OFFSET OF WHERE TABLE IS MOV [BX].VECOFF,PATCHED ; TO FIRST WORD OF RESPONSE AREA PATCH_OFF EQU WORD PTR $-2 ;THE ACTUAL VALUE OF THE IMMEDIATE IS PATCHED IN ;PASS SEGID OF WHERE TABLE IS MOV [BX].VECSEG,PATCHED ; TO SECOND WORD OF RESPONSE AREA PATCH_SEG EQU WORD PTR $-2 ;THE ACTUAL VALUE OF THE IMMEDIATE IS PATCHED IN ; $ENDIF $$IF3: MOV AL,INSTALLED ;SAY "INSTALLED" ; $ENDIF $$IF2: IRET ;RETURN TO INTERRUPT INVOKER ; $ENDIF $$IF1: ;SINCE THE MULTIPLEX NUMBER IS FOR SOMEBODY ELSE, PASS THE CALL ON TO PREVIOUS OWNER JMPREV: ;REFERENCED WHEN PATCHING OUT "DUMMY" JMP DUMMY ;CHAIN ON TO THE PREVIOUS OWNER ; OF THE VECTOR AT 1FH*4. ; USAGE OF "DUMMY" HERE IS JUST A PLACE-HLDER ; WHICH WILL BE REPLACED DURING EXECUTION OF LOADER PATHLABL GRTABHAN ;AN006; ;================================================================= HEADER ; $SALUT (4,14,20,41) PREV_OWN EQU DWORD PTR JMPREV+1 ;REFERENCED DURING REPLACEMENT OF "HANDLER" ; IN THE ABOVE JMP INSTRUCTION HANDLER ENDP IF ($-CSEG) MOD 16 ;IF NOT ALREADY ON 16 BYTE BOUNDARY ORG ($-CSEG)+16-(($-CSEG) MOD 16) ;ADD PADDING TO GET TO 16 BYTE BOUNDARY ENDIF HANDLER_SIZE EQU ($-CSEG)-(END_PSP-CSEG) ;MARK THE END OF RESIDENT EXECUTABLE ;AN000; PUBLIC HANDLER_SIZE ; PORTION, NOT INCLUDING THE PSP ;AN000; CSEG ENDS END END_PSP