#include <gdt.h>

void write_tss(struct tss_entry *tss, struct gdt_entry *gdt, int num, uint16_t ss0, uint32_t esp0) {
    uint32_t base = (uint32_t)tss;
    uint32_t limit = base + sizeof(struct tss_entry);

    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 |= 0x40;
    gdt[num].access = 0x89;

    memset(&tss, 0, sizeof(struct tss_entry));
    tss->ss0 = ss0;
    tss->esp0 = esp0;
    tss->cs = 0x0b;
    tss->ss = tss->ds = tss->es = tss->fs = tss->gs = 0x13;
}

void tss_flush(uint16_t tss_selector) {
    asm volatile (
        "ltr %0"
        : // no output
        : "r" (tss_selector)
    );
}