Date: 4 December 89, 09:53:09 EDT
From: Antonio@garcon.cso.uiuc.edu, Quezada-Duarte@garcon.cso.uiuc.edu,
Subject: Disabling CTRL-ALT-DEL
Marcelo H. Ang Jr in his letter dated Nov 11th 1989 asks for a program
逆@风@者
to disable CTRl ALT DEL, well.., here it is, i've used it on my
TANDY 1000A with no problems and in PS/2's 25 and 50 and had no
problems at all either.
To use it just type, from the dos prompt:
MASM NOCAD; (of course you need MASM)
LINK NOCAD; (and of course you need a linker)
NOCAD
If you type NOCAD once it has been loaded, it will tell you so.
I've used it with DOS 3.30, but it works just as well under DOS
2.00 and above.
If you have any comment of any kind please let me know.
And have a nice new decade everybody.
cut here: ************************************************************
page 255,132 ;just to get a nice list file
comment :
Program to prevent CTRL ALT DEL from restarting the system
WARNING: Once loaded, you only have three choices:
1) Turn power off
2) Use a reset button (not all the machines have one)
3) Generate INT 19h
WARNING: If you have a program that uses INT 0CDh, change
this value in the equates line below to the number
of a not used INT. This method is used because
there are too many programs that hook INT 9 Vector and
we can't be sure it always points to the end of our
notice (and start of our ISR).
NOTE: For memory references i use parentheses instead of
square brackets because of ASCII-EBCDIC translations.
It works the same under Microsoft's MASM 4.0
NOTE: NOCAD won't work if you press CTRL ALT DEL from
a program that hooked to INT 9 before NOCAD
(example: SideKick). Solution: Load NOCAD before
everything else.
Author Antonio Quezada-Duarte
Monterrey, Nuevo Leon, MEXICO
Monterrey's Technologic Institute
ID No 296641
Bitnet Address AL296641@TECMTYVM
BL296641@TECMTYVM
Feel free to share this with anyone while
leaving the copyright notice intact.
If you have any comment please let me know,thanks. :
ctrl equ 0100b ;bit map for ctrl key
alt equ 1000b ;bit map for alt key
free_vector equ 0CDh ;vector used to prevent double loading
;change it if your system uses INT 0CDh
nocad segment byte 'CODE'
assume cs:nocad, ds:msgs, es:nothing, ss:stack
Copyright db 'Antonio Quezada-Duarte ITESM ISC 296641 Monterrey '
db 'Nuevo Leon MEXICO'
Cright_Len equ $-Offset Copyright
new_int_9h proc near
push ax
push ds ;save registers
xor ax,ax
mov ds,ax ;point DS to BIOS data area
;well, actually BIOS data area
;starts at 0040:0000, but
; XOR AX,AX is faster than MOV AX,40h
mov al,ds:(417h) ;get keyboard flags
and al,ctrl alt ;clear non relevant bits
cmp al,ctrl alt ;compare to our map
jne go_ahead ;NO CTRL ALT keys pressed
and byte ptr ds:(417h),not alt ;CTRL ALT pressed
;clear ALT key bit to simulate
;ALT key is not pressed
go_ahead:
pushf ;old ISR returns with IRET
COMMENT :
The Following code stands for
CALL OLD_INT_9
Where OLD_INT_9 is a FAR PROC
this is faster than having the address of OLD_INT_9
stored in memory and doing a
CALL CS:(OLD_INT_9)
:
DB 9Ah
OLD_INT_9_OFS DW 0
OLD_INT_9_SEG DW 0 ;call old INT 9 ISR
pop ds
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