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tiny64os Architecture Overview

This is a small map of how the current system boots and where the major pieces live.

Boot flow

  1. GRUB loads the kernel through Multiboot2.
  2. The 32-bit bootstrap code:
    • verifies Multiboot handoff
    • checks CPU support
    • sets up the early page tables
    • enables long mode
  3. Control transfers into 64-bit assembly startup.
  4. 64-bit startup calls kernel_main().
  5. The C kernel initializes:
    • console / boot output
    • IDT
    • PIC remap
    • PIT timer
    • keyboard IRQ support
    • shell

Major subsystems

Boot / CPU bring-up

Files:

  • arch/x86_64/impl/boot/header.asm
  • arch/x86_64/impl/boot/main.asm
  • arch/x86_64/impl/boot/main64.asm

Responsibilities:

  • Multiboot2 header
  • early CPU checks
  • initial paging setup
  • transition to long mode
  • transfer into C

Kernel entry

File:

  • arch/x86_64/impl/kernel/main.c

Responsibilities:

  • high-level bring-up order
  • boot log flow
  • shell handoff

VGA console / text output

Files:

  • arch/x86_64/impl/print.c
  • arch/x86_64/intf/print.h

Responsibilities:

  • writing to VGA text memory
  • newline / scrolling behavior
  • cursor updates
  • integer / hex helpers
  • optional serial mirroring during boot

Interrupts and faults

Files:

  • arch/x86_64/impl/idt.c
  • arch/x86_64/impl/interrupts.asm
  • arch/x86_64/intf/idt.h
  • arch/x86_64/intf/interrupts.h

Responsibilities:

  • IDT setup
  • exception entry stubs
  • IRQ entry stubs
  • fault reporting

PIC and PIT

Files:

  • arch/x86_64/impl/pic.c
  • arch/x86_64/impl/pit.c
  • arch/x86_64/intf/pic.h
  • arch/x86_64/intf/pit.h

Responsibilities:

  • PIC remap
  • IRQ masking / unmasking
  • PIT initialization
  • tick counting

Keyboard input

Files:

  • arch/x86_64/impl/keyboard.c
  • arch/x86_64/intf/keyboard.h

Responsibilities:

  • PS/2 scancode handling
  • modifier tracking
  • shell navigation keys
  • Ctrl-C handling

Shell

Files:

  • arch/x86_64/impl/shell.c
  • arch/x86_64/intf/shell.h

Responsibilities:

  • prompt and command loop
  • line editing
  • history recall
  • built-in commands

Serial logging

Files:

  • arch/x86_64/impl/serial.c
  • arch/x86_64/intf/serial.h

Responsibilities:

  • COM1 initialization
  • serial character / string output
  • boot diagnostics outside VGA

Port I/O helpers

Files:

  • arch/x86_64/impl/io.c
  • arch/x86_64/intf/io.h

Responsibilities:

  • inb
  • outb
  • tiny I/O wait helper

Directory layout

arch/x86_64/impl/
  boot/         bootstrap asm and long-mode entry
  kernel/       high-level kernel startup
  *.c           subsystem implementations
  *.asm         interrupt / low-level assembly glue

arch/x86_64/intf/
  *.h           subsystem interfaces

targets/x86_64/
  linker.ld     linker script
  iso/          GRUB boot tree used to build kernel.iso

buildenv/
  Dockerfile    reproducible build environment

pics/
  screenshots / images

Current architectural shape

tiny64os is best thought of as:

  • a bootable x86_64 kernel
  • a text console environment
  • a hardware-interrupt example that is already usable
  • a compact base for learning how these pieces fit together

The goal here is not to become huge quickly. The goal is to stay readable while still showing a real interrupt-driven system with a basic shell.