From:	mpenacho AT tezcat DOT com (Mark Penacho)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Hooking interrupts
Date:	Sat, 18 Jan 97 05:01:13 GMT
Organization:	Tezcat.COM - Specialists in human interconnectivity.
Lines:	69
Message-ID:	<5bples$dql@tepe.tezcat.com>
References:	<32E045B5 DOT 4680 AT mail DOT idt DOT net>
NNTP-Posting-Host:	mpenacho.tezcat.com
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

In article <32E045B5 DOT 4680 AT mail DOT idt DOT net>, Joseph Turian <turian AT mail DOT idt DOT net> wrote:
>Is it possible to hook an interrupt while in protected mode? I wanted
>to write a keyboard handler, but I am new to djgpp and only know how
>it is done in 8086 assembly
#include <go32.h>
#include <dpmi.h>

_go32_dpmi_seginfo   old_keyboard_isr;
_go32_dpmi_seginfo   keyboard_interrupt_holder;
int raw_scan_code;

void init_keyboard(void) {
   while(kbhit())
      getch();

   _go32_dpmi_lock_code(keyboard_irq, (ADDRESS)end_keyboard_irq  -  \
        (ADDRESS)_keyboard_irq);
   _go32_dpmi_lock_code(key_asm, 30);
   _go32_dpmi_lock_data(&raw_scan_code,sizeof(raw_scan_code));
   _go32_dpmi_lock_data  (ALL OTHER KEYBOARD IRQ VARIABLES)

   _go32_dpmi_get_protected_mode_interrupt_vector(KEYBOARD_INT,  \
        &old_keyboard_isr)
   keyboard_interrupt_holder.pm_offset = (ADDRESS)keyboard_irq;
   _go32_dpmi_allocate_iret_wrapper(&keyboard_interrupt_holder);
   _go32_dpmi_set_protected_mode_interrupt_vector(KEYBOARD_INT,  \
        &keyboard_interrupt_holder);
}

void uninit_keyboard() {
    _go32_dpmi_set_protected_mode_interrupt_vector(KEYBOARD_INT, \
        &old_keyboard_isr);
   _go32_dpmi_free_iret_wrapper(&keyboard_interrupt_holder);
}

void keyboard_irq(void) {
   key_asm();
   DO SOMETHING WITH raw_scan_code;
}

int end_keyboard_irq(void) {  // do something unique to guarantee \
                                         //optimization doesn't overrride
   return(4);
}


assembly part (I use nasm, your code may vary)

[BITS 32]
[GLOBAL _key_asm]
[EXTERN _raw_scan_code]
[SECTION .text]

_key_asm:
        sti
        xor     eax,eax
        in      al,60h
        mov     dword [_raw_scan_code],eax
        in      al,61h
        or      al,82h
        out     61h,al
        and     al,7fh
        out     61h,al
        mov     al,20h
        out     20h,al
        ret

- Raw text -