#include "gdt.h"

struct gdt_entry gdt[3];
struct gdt_ptr gdtp;

extern void gdt_flush(uint32_t);

void gdt_set_gate(int num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran) {
    gdt[num].base_low = (base & 0xFFFF);
    gdt[num].base_middle = (base >> 16) & 0xFF;
    gdt[num].base_high = (base >> 24) & 0xFF;

    gdt[num].limit_low = (limit & 0xFFFF);
    gdt[num].granularity = (limit >> 16) & 0x0F;

    gdt[num].granularity |= gran & 0xF0;
    gdt[num].access = access;
}

void gdt_install() {
    gdtp.limit = (sizeof(struct gdt_entry) * 3) - 1;
    gdtp.base = (uint32_t)&gdt;

    gdt_set_gate(0, 0, 0, 0, 0);                // Null segment
    gdt_set_gate(1, 0, 0xFFFFFFFF, 0x9A, 0xCF); // Code segment
    gdt_set_gate(2, 0, 0xFFFFFFFF, 0x92, 0xCF); // Data segment

    gdt_flush((uint32_t)&gdtp);
}