FENIX_kernel/arch/i386/init.c

#include <kernel/init.h>
#include <kernel/interrupt.h>
#include <string.h>
#include <sys/io.h>
#include "gdt.h"

int tss[16][2];

void NMI_disable(void) {
  outb(0x70, inb(0x70) | 0x80);
}

void NMI_enable(void) {
  outb(0x70, inb(0x70) & 0x7F);
}

void A20_enable(void) {
  unsigned short int a = inb(0x92);
  if((a & 2) != 0) {
    return;
  }
  a |= 2;
  outb(a, 0x92);
}

void setup_gdt(void) {
  struct GDT gdt[4];

  gdt[0].base = 0; gdt[0].limit = 0; gdt[0].type = 0;
  gdt[1].base = 0; gdt[1].limit = 0xFFFFFFFF; gdt[1].type = 0x9A;
  gdt[2].base = 0; gdt[2].limit = 0xFFFFFFFF; gdt[2].type = 0x92;
  gdt[3].base = (unsigned int) tss; gdt[3].limit=sizeof(tss); gdt[3].type = 0x89;

  unsigned short int GDT[4];
  encode_gdt_entry(&GDT[0], gdt[0]);
  encode_gdt_entry(&GDT[1], gdt[1]);
  encode_gdt_entry(&GDT[2], gdt[2]);
  encode_gdt_entry(&GDT[3], gdt[3]);

  set_gdt(GDT, sizeof(GDT));
}

int init(void) {
  NMI_disable();
  A20_enable();
  setup_gdt();
  idt_init();
  printf("Fenix Dev Pre-release v0.0.3\n");
  return 0;
}