Simtel MSDOS 1992 June

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/ Simtel MSDOS 1992 June / SIMTEL_0692.cdr / msdos / sysutl / safari2.arc / SAFARI.ASM < prev next >

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Assembly Source File | 1987-08-19 | 15.0 KB | 528 lines

;====================================================================== ; SAFARI - Staying Away From Abort, Retry, Ignore ; A resident interrupt handler for the DOS critical error handler ; Tested in PC-DOS 2.0 to 3.31 ;---------------------------------------------------------------------- CSEG SEGMENT PARA PUBLIC 'CODE' ASSUME CS:CSEG,DS:NOTHING,ES:NOTHING,SS:NOTHING ORG 100H ;SKIP TO END OF THE PSP ENTPT: JMP INITIALIZE ;COM FILE ENTRY ALWAYS AT 100H COPYRIGHT DB "SAFARI 1.0 (c) Ziff Communications Co.$" PROGRAMMER DB "Robert L. Hummel" ;---------------------------------------------------------------------- ; Program data area. Bufferes at end of resident code. ;---------------------------------------------------------------------- BOX_ATTR EQU 4FH ;Window color: 70 for b/w BCOL EQU 0 ;Window top left column BROW EQU 4 ;Window top left row NCOL EQU 46 ;Width of window NROW EQU 15 ;Length of window DISPLAY_PAGE DB 0 ;Hold current value CURSOR_POS DW 0 ;Hold current value OLD_INT_24 DD 0 ;Address of original Handler DI_REG DB 0,0 ;Local storage for error codes AX_REG DB 0,0 ; as low-byte, hi-byte ATTR_BYTE DB 0 ;From device header ; Strings encoded as col, row, ASCIIZ HEADER DB BCOL,BROW,"<< SAFARI Critical Error Handler >>",0 DISK_ERR DB BCOL+1,BROW+1,"System Reports A Disk Error",0 CHAR_DEV_ERR DB BCOL+1,BROW+1,"System Reports A Character Device Error",0 BAD_FAT_ERR DB BCOL+1,BROW+1,"System Reports A Bad FAT",0 ERR_TABLE DW ERR0,ERR1,ERR2,ERR3,ERR4,ERR5,ERR6,ERR7 DW ERR8,ERR9,ERRA,ERRB,ERRC ERR0 DB BCOL+1,BROW+2 DB "Attempt To Write On Write-Protected Diskette",0 ERR1 DB BCOL+1,BROW+2,"Unknown Or Bad Unit",0 ERR2 DB BCOL+1,BROW+2,"Drive Not Ready",0 ERR3 DB BCOL+1,BROW+2,"Unknown Command",0 ERR4 DB BCOL+1,BROW+2,"Data Error (CRC)",0 ERR5 DB BCOL+1,BROW+2,"Bad Request Structure Length",0 ERR6 DB BCOL+1,BROW+2,"Seek Error",0 ERR7 DB BCOL+1,BROW+2,"Unknown media type",0 ERR8 DB BCOL+1,BROW+2,"Sector Not Found",0 ERR9 DB BCOL+1,BROW+2,"Printer Out Of Paper",0 ERRA DB BCOL+1,BROW+2,"Write Fault",0 ERRB DB BCOL+1,BROW+2,"Read Fault",0 ERRC DB BCOL+1,BROW+2,"General Failure",0 DRIVE_MSG DB BCOL+1,BROW+3,"On Drive " DRIVE_NAME DB "A:",0 READ_OPER DB BCOL+1,BROW+4,"During A Read Operation",0 WRITE_OPER DB BCOL+1,BROW+4,"During A Write Operation",0 AREA_MSG DB BCOL+1,BROW+5,"Error Localized In",0 AREA_TABLE DW DOS_AREA,FAT_AREA,DIR_AREA,DATA_AREA DOS_AREA DB BCOL+1,BROW+6,"DOS Area",0 FAT_AREA DB BCOL+1,BROW+6,"File Allocation Table",0 DIR_AREA DB BCOL+1,BROW+6,"Directory Area",0 DATA_AREA DB BCOL+1,BROW+6,"Data Area",0 REG_BLK1 DB BCOL+1,BROW+ 8,"AX=0000 BX=0000 CX=0000 DX=0000",0 REG_BLK2 DB BCOL+1,BROW+ 9,"DS=0000 SI=0000 ES=0000 DI=0000",0 REG_BLK3 DB BCOL+1,BROW+10,"CS:IP=0000:0000",0 ;====================================================================== ; Control is passed here by the jump we inserted into the DOS Int 24 handler ;---------------------------------------------------------------------- INT_24 PROC FAR STI ;Allow Interrupts PUSH AX ;Save used registers PUSH DS MOV DS,BP ;Get Device Header attribute MOV AX,[SI+4] ; byte before changing BP MOV CS:ATTR_BYTE,AH POP DS ;Restore POP AX PUSH BP ;Access to stack MOV BP,SP ;Before we push anything MOV WORD PTR CS:AX_REG,AX ;Error status MOV WORD PTR CS:DI_REG,DI ;Error code in lower half PUSHF ;Save the state of the machine PUSH ES ; because we're gonna make PUSH DS ; a mess of it PUSH DI PUSH SI PUSH DX PUSH CX PUSH BX PUSH AX MOV AX,CS ;Set up access to local data MOV DS,AX MOV ES,AX ASSUME DS:CSEG, ES:CSEG ;Tell the assembler ;---------------------------------------------------------------------- ; Save the details of the current screen for later restoration. ;---------------------------------------------------------------------- MOV AH,0FH ;Get current video mode fn INT 10H ;Thru BIOS MOV DISPLAY_PAGE,BH ;Save current page MOV AH,3 ;Get cursor position fn INT 10H ;Thru BIOS MOV CURSOR_POS,DX ;Save position for ;restoration on exit ;---------------------------------------------------------------------- ; Save section of screen we will be writing over. ;---------------------------------------------------------------------- MOV BH,DISPLAY_PAGE CLD ;String moves forward MOV DI,OFFSET SCREEN_BUFFER ;Destination for save MOV CX,NROW ;Row loop MOV DH,BROW ;Init row pointer ROW_LOOP1: PUSH CX ;Prepare for... MOV CX,NCOL ;...column loop MOV DL,BCOL ;Column Pointer COL_LOOP1: MOV AH,2 ;Position cursor fn INT 10H ;Thru BIOS MOV AH,8 ;Get char & attribute fn INT 10H ;Thru BIOS STOSW ;ES:[di]<-ax ; di+=2 INC DL ;Next column LOOP COL_LOOP1 ;Close Inner loop POP CX ;Return to outer loop INC DH ;Next row LOOP ROW_LOOP1 ;Close Outer loop ;---------------------------------------------------------------------- ; Clear a window (box) for our information on the screen. ;---------------------------------------------------------------------- MOV AH,6 ;Scroll window fn MOV AL,0 ;Scroll entire window MOV CH,BROW ;Upper row MOV CL,BCOL ;Left column MOV DH,BROW + NROW - 1 ;Bottom row is lower MOV DL,BCOL + NCOL - 1 ;Right column MOV BH,BOX_ATTR ;Window color INT 10H ;Thru BIOS ;---------------------------------------------------------------------- ; Say who we are and give some information as to what happened. ;---------------------------------------------------------------------- MOV SI,OFFSET HEADER CALL WR_STRING ;---------------------------------------------------------------------- ; if ( AH:7 == 0 ) ; disk_error ; else if ( ATTR_BYTE:7 == 0 ) ; bad_fat ; else ; character_device ;---------------------------------------------------------------------- MOV SI,OFFSET DISK_ERR ;AH IS ERROR, DI OK TEST AX_REG[1],80H ;Hi bit=0 if disk error JZ HARD_ERROR ;Print and examine AL MOV SI,OFFSET CHAR_DEV_ERR ;Check Header for Bad Fat err TEST ATTR_BYTE,80H JNZ DI_CODE ;else non-block device MOV SI,OFFSET BAD_FAT_ERR HARD_ERROR: CALL WR_STRING MOV AL,AX_REG[0] ;Failing drive code ADD AL,'A' ; convert to ascii MOV DRIVE_NAME,AL ; and put in display string MOV SI,OFFSET DRIVE_MSG ;In drive... CALL WR_STRING MOV SI,OFFSET READ_OPER ;Say what operation TEST AX_REG[1],1 ;0=Read, 1=Write JZ A20 MOV SI,OFFSET WRITE_OPER A20: CALL WR_STRING MOV SI,OFFSET AREA_MSG ;Say what area CALL WR_STRING XOR BH,BH ;Leaving the area bits one MOV BL,AX_REG[1] ; position to the left is the AND BL,6 ; same as multiplying by two MOV SI,AREA_TABLE[BX] ;Offset into pointer table DI_CODE: CALL WR_STRING ;Interpret code in DI XOR BH,BH MOV BL,DI_REG ;Get error code SHL BX,1 ;Make offset into table (*2) MOV SI,ERR_TABLE[BX] CALL WR_STRING ;---------------------------------------------------------------------- ; Perform a rudimentary traceback. Display the available registers of the ; original Int 21 and the program location it was called from. ;---------------------------------------------------------------------- MOV DI,OFFSET REG_BLK1 + 5 ;Put digits here MOV AX,[BP+8] ;Point to word on stack CALL HEX4 ;Convert to ascii in string ADD DI,8 ;Point to next location MOV AX,[BP+10] ;...continue the process CALL HEX4 ADD DI,8 MOV AX,[BP+12] CALL HEX4 ADD DI,8 MOV AX,[BP+14] CALL HEX4 MOV SI,OFFSET REG_BLK1 CALL WR_STRING MOV DI,OFFSET REG_BLK2 + 5 ;Repeat for 2nd set of REGS MOV AX,[BP+22] CALL HEX4 ADD DI,8 MOV AX,[BP+16] CALL HEX4 ADD DI,8 MOV AX,[BP+24] CALL HEX4 ADD DI,8 MOV AX,[BP+18] CALL HEX4 MOV SI,OFFSET REG_BLK2 CALL WR_STRING MOV DI,OFFSET REG_BLK3 + 8 ;Repeat for CS and IP MOV AX,[BP+28] CALL HEX4 ADD DI,5 MOV AX,[BP+26] CALL HEX4 MOV SI,OFFSET REG_BLK3 CALL WR_STRING MOV BH,DISPLAY_PAGE ;Position for the ARI? msg MOV DH,BROW + 12 ;DH=row MOV DL,BCOL ;DL=col MOV AH,2 ;Set cursor posn fn INT 10H ;Thru BIOS ;---------------------------------------------------------------------- ; Restore the state of the machine when Int 24 occured ;---------------------------------------------------------------------- POP AX POP BX POP CX POP DX POP SI POP DI POP DS POP ES POPF POP BP ASSUME DS:NOTHING, ES:NOTHING ;---------------------------------------------------------------------- ; Here is the original Int 24 handler splice. Simulate an interrupt ;---------------------------------------------------------------------- PUSHF ;Push the flags CLI ;Disable interrupts PUSH CS ;Push the CS register MOV DI,OFFSET CS:RET_TARGET ;Get addr of next instr. PUSH DI ; on stack too. MOV DI,WORD PTR CS:DI_REG ;Restore register PREFIX: DB 5 DUP(?) ;First 5 bytes of old 24h JMP DWORD PTR CS:OLD_INT_24 ;Transfer control to old 24h ;---------------------------------------------------------------------- ; IRET transfers control here. Again, save the machine state and set up ; registers to acess data. ;---------------------------------------------------------------------- RET_TARGET: PUSHF PUSH ES PUSH DS PUSH BP PUSH DI PUSH SI PUSH DX PUSH CX PUSH BX PUSH AX MOV AX,CS MOV DS,AX MOV ES,AX ASSUME DS:CSEG, ES:CSEG ;Tell the assembler ;---------------------------------------------------------------------- ; Restore the screen to original state. ;---------------------------------------------------------------------- MOV BH,DISPLAY_PAGE ;Just to be sure, reset page MOV AH,2 ;Set cursor position fn MOV DH,BROW ;Top of window MOV DL,BCOL ;Column INT 10H ;Thru BIOS MOV SI,OFFSET SCREEN_BUFFER ;Origin for restoration MOV CX,NROW ;Row loop MOV DH,BROW ;Init row pointer ROW_LOOP2: PUSH CX ;Prepare for... MOV CX,NCOL ;...column loop MOV DL,BCOL ;Column Pointer COL_LOOP2: PUSH CX ;Need for write-char fn MOV AH,2 ;Position cursor fn INT 10H ;Thru BIOS LODSW ;AX <- [SI] ;AH=ATTR AL=CHAR MOV BL,AH ;Put attribute where needed MOV AH,9 ;Write char fn MOV CX,01 ;Write one copy of char INT 10H ;Thru BIOS INC DL ;Next column POP CX ;Restore Counter LOOP COL_LOOP2 ;Close Inner loop POP CX ;Return to outer loop INC DH ;Next row LOOP ROW_LOOP2 ;Close Outer loop MOV AH,2 ;Set Cursor position fn MOV DX,CURSOR_POS ;Restore old cursor position INT 10H ;Thru BIOS POP AX POP BX POP CX POP DX POP SI POP DI POP BP POP DS POP ES POPF IRET ;And we return too INT_24 ENDP ;====================================================================== ; All access to the BIOS video interrupt comes through here. Some BIOSs ; destroy BP during a INT 10h call. ;---------------------------------------------------------------------- VIDEO PROC NEAR PUSH BP INT 10H POP BP RET VIDEO ENDP ;====================================================================== ; HEX4 - Convert the AX register to hexidecimal digits. ; The characters produced are stored at ES:DI. ; All regs preserved. ;---------------------------------------------------------------------- HEX4 PROC NEAR PUSH AX PUSH BX PUSH CX MOV BX,AX STD ;String ptr decrement ADD DI,3 ;Point to end of string MOV CX,4 H10: MOV AL,BL ;Want lower half AND AL,0FH ; of this byte ADD AL,90H ;Convert AL to ASCII DAA ADC AL,40H DAA STOSB ;Store at ES:DI SHR BX,1 SHR BX,1 SHR BX,1 SHR BX,1 LOOP H10 POP CX POP BX POP AX INC DI CLD RET HEX4 ENDP ;====================================================================== ; WR_STRING - write string to console at specified location. ; The first two bytes of the string contain the column and row of the ; display location. The remainder of the string is ASCIIZ. ; AX is destroyed, all other registers are preserved. ;---------------------------------------------------------------------- WR_STRING PROC NEAR PUSH BX PUSH DX PUSH SI MOV BH,DISPLAY_PAGE MOV DX,[SI] ;DH=row, DL=col MOV AH,2 ;Set cursor posn fn INT 10H ;Thru BIOS INC SI ;Point to start of string INC SI NEXT_CHAR: LODSB ;Load char in AL from DS:SI OR AL,AL ;If char is 0 JZ END_STRING ;End of ASCIIZ string MOV AH,0EH ;Else, write TTY INT 10H ;Thru BIOS JMP SHORT NEXT_CHAR END_STRING: POP SI POP DX POP BX RET WR_STRING ENDP ;====================================================================== PC = $ SCREEN_BUFFER = PC PC = PC + NROW * NCOL * 2 LASTBYTE = PC ;====================================================================== ; Initialization Procedure ; Patch command.com to load our handler as the new default ;---------------------------------------------------------------------- INITIALIZE PROC NEAR ASSUME CS:CSEG,DS:CSEG,ES:CSEG,SS:CSEG ;Set by loader. MOV AH,9 MOV DX,OFFSET COPYRIGHT INT 21H ;---------------------------------------------------------------------- ; Get the current address of Int 24 and save ;---------------------------------------------------------------------- MOV AH,35H ;Get Int vector MOV AL,24H ;For this Int INT 21H ;Result in ES:BX ASSUME ES:NOTHING CMP BYTE PTR ES:[BX],0EAH ;If code is jump JNE NOT_INSTALLED MOV AX,4C01H ;Terminate with error INT 21H NOT_INSTALLED: MOV WORD PTR OLD_INT_24[0],BX ;offset MOV WORD PTR OLD_INT_24[2],ES ;segment ;---------------------------------------------------------------------- ; Copy the first five bytes of the DOS Int 24 handler to our handler. ;---------------------------------------------------------------------- MOV CX,5 ;Move 5 bytes PUSH ES ;From old handler (DS:SI) POP DS ASSUME DS:NOTHING MOV SI,BX PUSH CS ;To a safe place (ES:DI) POP ES ASSUME ES:CSEG MOV DI,OFFSET PREFIX REP MOVSB ;---------------------------------------------------------------------- ; Build our jump command inside the original Int 24 handler to ; pass control immediately to our handler. ;---------------------------------------------------------------------- PUSH DS ;Point ES to POP ES ; the old handler ASSUME ES:NOTHING MOV DI,BX ;Write to ES:DI MOV AL,0EAH ;Opcode for far jump STOSB MOV AX,OFFSET INT_24 ;Offset of our handler STOSW MOV AX,CS STOSW ADD WORD PTR CS:OLD_INT_24,5 ;Point after jump ;---------------------------------------------------------------------- ; Terminate and stay resident. ;---------------------------------------------------------------------- MOV AX,3100H MOV DX,(OFFSET LASTBYTE - OFFSET CSEG + 15) SHR 4 INT 21H INITIALIZE ENDP CSEG ENDS END ENTPT