buh

#include <stdio.h>

#include <kernel/tty.h>
#include <kernel/gdt.h>
#include <kernel/idt.h>
#include <kernel/timer.h>
#include <kernel/port_io.h>

#define PORT 0x3F8

void kernel_main(void) {
   outb(PORT + 1, 0x00);    // Disable all interrupts
   outb(PORT + 3, 0x80);    // Enable DLAB (set baud rate divisor)
   outb(PORT + 0, 0x03);    // Set divisor to 3 (lo byte) 38400 baud
   outb(PORT + 1, 0x00);    //                  (hi byte)
   outb(PORT + 3, 0x03);    // 8 bits, no parity, one stop bit
   outb(PORT + 2, 0xC7);    // Enable FIFO, clear them, with 14-byte threshold
   outb(PORT + 4, 0x0B);    // IRQs enabled, RTS/DSR set
   outb(PORT + 4, 0x1E);    // Set in loopback mode, test the serial chip
   outb(PORT + 0, 0xAE);    // Test serial chip (send byte 0xAE and check if serial returns same byte)
  outb(PORT + 4, 0x0F);
  tty_init();

  gdt_init();
  printf("Initialised GDT.\n");
  idt_init();
  printf("Initialised IDT.\n");
  timer_init();
  while (1) {
    outb(0x43, 0x00);
    uint8_t res = inb(0x40);
    outb(0x3F8, res);
  }
}

(ran with qemu-system-i386 -serial file:log.txt -cdrom sillyos.iso)