Question

I am working on Atom-32bit board (AT&T assembly), there is no software on this board yet.

Do I need to build GDT to build/use an IDT ?

The idea is just to use an ISR with APIC timer.

/*Change the address of idt_entries table */
fill_interrupt(ISR_Nbr,(unsigned int) isr33, 0x08, 0x8E);


static void fill_interrupt(unsigned char num, unsigned int base, unsigned short sel, unsigned char flags)
{
    unsigned short *Interrupt_Address;

    /*address = idt_ptr.base + num * 8 byte*/
    Interrupt_Address = (unsigned short *)(idt_ptr.base + num*8);

    *(Interrupt_Address) = base&0xFFFF;
    *(Interrupt_Address+1) = sel;
    *(Interrupt_Address+1) = (flags>>8)&0xFF00;
    *(Interrupt_Address+1) = (base>>16)&0xFFFF;

}

Answer 1

Resolved :), as there is a BIOS, it already built the GDT/IDT, so I found there address using sidt and sgdt instructions, and i added my ISR to sidt