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Index > OS Construction > Masking alt - del

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GhostXoPCorp



Joined: 13 Dec 2008
Posts: 199
Location: 01F0:0100
GhostXoPCorp
is there a way that i could mask alt del to not restart the computer in real mode?

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Oh that divide overflow. Just jumps out of the bushes every time to scare the day lights out of me.
Post 15 Jun 2009, 00:55
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17250
Location: In your JS exploiting you and your system
revolution
Do you mean CTRL-ALT-DEL?

In real mode you can just take over the kdb interrupt and do what you like with the keystrokes. When you see DEL pressed and CTRL and ALT are already down then just bypass the callback into the BIOS so that the keystroke is ignored.
Post 15 Jun 2009, 01:00
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
Quote:

In real mode you can just take over the kdb interrupt and do what you like with the keystrokes. When you see DEL pressed and CTRL and ALT are already down then just bypass the callback into the BIOS so that the keystroke is ignored.

Can you really forward the interrupt 9 to the BIOS after doing this? I mean, what keyboard controller state the BIOS will receive if you had to read the keyboard port first?
Post 15 Jun 2009, 01:37
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sinsi



Joined: 10 Aug 2007
Posts: 692
Location: Adelaide
sinsi
Best way is to hook int 15h, AH=4fh
Quote:

called by INT 09 handler to translate scan codes; the INT 09 code does not examine the scan code it reads from the keyboard until after this function returns.
Post 15 Jun 2009, 02:10
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GhostXoPCorp



Joined: 13 Dec 2008
Posts: 199
Location: 01F0:0100
GhostXoPCorp
is there a way where i can check the buffer for ctrl alt del or just alt del and then jump back into getting keys, or is reprogramming the keyboard controller inturrupt the only way?
ps alt del restarts the system also

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Oh that divide overflow. Just jumps out of the bushes every time to scare the day lights out of me.
Post 15 Jun 2009, 03:12
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sinsi



Joined: 10 Aug 2007
Posts: 692
Location: Adelaide
sinsi
ctrl-alt-del never gets to the buffer, the system is rebooted from within the BIOS's INT 9 handler. Hook int 15, function 4f and check for the delete key then check ctrl and alt. If they are all pressed, you just tell the int9 handler to ignore it and nothing happens.
Post 15 Jun 2009, 03:24
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GhostXoPCorp



Joined: 13 Dec 2008
Posts: 199
Location: 01F0:0100
GhostXoPCorp
hows ths, when int 9 call a restart, is the restart it calls in another intturupt? int 19? if so, could i just over write int 19 to ask the user

Restart y)es n)o?

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Oh that divide overflow. Just jumps out of the bushes every time to scare the day lights out of me.
Post 15 Jun 2009, 04:53
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DOS386



Joined: 08 Dec 2006
Posts: 1901
DOS386
> just take over the kdb interrupt

or just disable it completely. You still can peek keystrokes then.
Post 15 Jun 2009, 15:23
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