os/arch/i686/interrupt.c

#include <kernel/tty.h>
#include <debugging.h>
#include <stdint.h>
#include <stddef.h>

#define NUM_ENTRIES 0

struct InterruptDescriptor {
    uint32_t offset;
    uint32_t selector;
    uint8_t gate_type;
    uint8_t ring;
    bool present;
};

struct IDT {
    uint16_t size;
    uint64_t* base;
} __attribute__((packed));

static uint64_t entries[NUM_ENTRIES];
static size_t current_entry = 0;
struct IDT idt;

static void encodeIdtEntry(uint8_t *target, struct InterruptDescriptor source)
{
    // Encode the present bit
    if (source.present) {
        target[5] |= 0xF0;
    } else {
        // Not present, return
        return;
    }

    // Encode the offset 
    target[0] = (source.offset >> 0x00) & 0xFF;
    target[1] = (source.offset >> 0x08) & 0xFF;
    target[6] = (source.offset >> 0x10) & 0xFF;
    target[7] = (source.offset >> 0x18) & 0xFF;
    
    // Encode the base
    target[2] = (source.selector >> 0x00) & 0xFF;
    target[3] = (source.selector >> 0x08) & 0xFF;
    
    // Encode the gate type
    target[5] |= source.gate_type;
    
    // Encode the DPL
    target[5] |= (source.ring >> 5);
    
    print_hex_bytes(target, 8);
}

static void add_entry(struct InterruptDescriptor entry)
{
    if (current_entry == NUM_ENTRIES) {
        terminal_writestring("WARNING: More IDT entries than NUM_ENTRIES.\n");
        return;
    }

    uint64_t descriptor = 0;
    encodeIdtEntry((uint8_t*) &descriptor, entry);

    entries[current_entry] = descriptor;

    current_entry++;
}

static void load_idt() 
{
    idt.size = NUM_ENTRIES * 8 - 1;
    idt.base = entries;

    for (int i = 0; i < NUM_ENTRIES; i++) {
        print_hex_bytes(idt.base + i, 8);
        terminal_putchar('\n');
    }

    asm ( "lidt %0" : : "m"(idt) );
}

void idt_init()
{
    terminal_writestring("TODO: Add interrupts");
    terminal_putchar('\n');

    // load_idt();
}