irq_common_stub:
   pusha

   mov ax,ds
   push eax

   mov ax,0x10
   mov ds,ax
   mov es,ax
   mov fs,ax
   mov gs,ax

   push esp
   cld

   call irq_handler
   pop ebx
   pop ebx
   mov ds,bx
   mov es,bx
   mov fs,bx
   mov gs,bx
   popa
   add esp, 8
   iret

; ......
irq0:   
   push byte 0
   push byte 32
   jmp irq_common_stub
; etc ...

extern "C" void irq_handler(registers_t *r){
   // send end of interrupt to pics after each interrupt
   // or they wont send another one
   //kprint("recevied irq\n");
   if(r->int_no > 33){
      kprint("error: ");
      char st[3];
      int_to_ascii(r->int_no,st);
      kprint(st);
      kprint("\n");
      return;
   }

   if(r->int_no >= 40) port_byte_out(0xA0, 0x20); //slave
   port_byte_out(0x20,0x20); //master

   if(interrupt_handlers[r->int_no] != 0){
      isr_t handler = interrupt_handlers[r->int_no];
      handler(r);
   }
}

void init_keyboard(){
   register_interrupt_handler(IRQ1, keyboard_callback);
}

void init_timer(uint32_t freq){
   //register handler
   register_interrupt_handler(IRQ0, timer_callback);

   //get the PIT value, hardware clock is 1193180 Hz
   uint32_t divisor = 1193180 / freq;
   uint8_t low = (uint8_t) (divisor & 0xFF);
   uint8_t high = (uint8_t)( (divisor >> 8) & 0xFF);
   //send the command
   port_byte_out(0x43, 0x36);
   port_byte_out(0x40,low);
   port_byte_out(0x40,high);

   //port_byte_out(0x20,0x20);
}