#include "gdt.h"

static struct gdt gdt = { 0 };

static void create_kernel_ds()
{
}

static void create_kernel_cs()
{
}

static void create_gdt()
{
    create_kernel_ds();
    create_kernel_cs();
}

static void load_gdt()
{
    struct gdt_r gdtr;
    gdtr.addr = (uint32_t)&gdt;
    gdtr.limit = GDT_SIZE - 1;

    asm volatile("lgdt %0\n"
            :
            : "m" (gdtr)
            : "memory");
}

static void load_ds()
{
    struct segment_selector selector;
    selector.index = KERNEL_DS_INDEX;
    selector.table_indicator = 0;
    selector.rpl = 0;

    asm volatile("movw %0, %%ax\n"
                 "movw %%ax, %%ds\n"
                 "movw %%ax, %%fs\n"
                 "movw %%ax, %%gs\n"
                 "movw %%ax, %%ss\n"
            :
            : "m" (selector)
            : "ax");
}

static void load_cs()
{
    struct segment_selector selector;
    selector.index = KERNEL_CS_INDEX;
    selector.table_indicator = 0;
    selector.rpl = 0;

    asm volatile("pushl %0\n"
                 "pushl $1f\n"
                 "lret\n"
                 "1:\n"
             :
             : "m" (selector));
}

static void reload_segment_selectors()
{
    load_ds();
    load_cs();
}

void init_gdt()
{
    create_gdt();
    load_gdt();
    reload_segment_selectors();
}