TickTOS - A Real Time Operating System

Overview

This project to make a Real Time Operating System. This kernel runs in 32-bit Protected Mode, boots via GRUB, and includes basic timer and keyboard drivers, a custom heap allocator, and interrupt handling. Every feature of the kernel are the legacy features, assembly instructions, memory alignment, ELF structure and Multiboot spec.

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Features

1. Boot

• GRUB + Multiboot compliant

• Custom linker script for memory layout

• VGA text mode buffer

• Serial output for debugging

2. Descriptor Tables

• Global Descriptor Table (GDT)
• Interrupt Descriptor Table (IDT)

3. Interrupts & PIC

• CPU exceptions
• Hardware Interrupt (IRQ) handling
• PIC remapping

4. Drivers

• Keyboard driver to print pressed keys
• Timer driver to tick at 100 Hz

5. Memory Management

• Parse Multiboot memory map
• Print free blocks
• Initialize heap
• Implement kalloc and kfree with First-Fit approach
• Memory Alignment for heap and allocations

6. Debugging

• GDB with QEMU

• Inspect registers such as, PIC registers, EFLAGS and segment registers

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Project Structure

├── boot/ # Bootloader code (Multiboot header)
├── gdt/ # Global Descriptor Table setup
├── idt/ # Interrupt Descriptor Table & IRQs
│ ├── irq/ # IRQ handling
│ └── isr/ # Exception handling
├── drivers/ # Keyboard, Timer, Serial drivers
├── kernel/ # Core kernel logic & memory management
├── display/ # VGA text mode output
├── grub/ # GRUB config
├── include/ # Header files
├── iso/ # ISO build directory for GRUB boot
├── linker/ # Linker script
├── build/ # Compiled objects & ISO
└── Makefile # Build automation

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Requirements

• qemu-system-i386 or qemu-system-x86_64
• i686-elf-gcc cross-compiler
• make
• nasm
• gdb-multiarch (for debugging)

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Build

make

This generates:

• build/ticktos.elf – Kernel ELF binary

• build/ticktos.iso – Bootable ISO (GRUB)

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Run

Standard graphical mode:

qemu-system-i386 -cdrom build/ticktos.iso

Non-graphical with serial output:

qemu-system-i386 -cdrom build/ticktos.iso -nographic -serial mon:stdio

For older machine (to inspect PIC and disable APIC):

qemu-system-x86_64 -cdrom build/ticktos.iso -serial stdio -machine isapc

To log output to a file:

qemu-system-x86_64 -cdrom build/ticktos.iso -serial stdio -machine isapc > qemu.log 2>&1

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Debug With GDB

Run QEMU in debug mode:

qemu-system-i386 -cdrom build/ticktos.iso -nographic -serial mon:stdio -s -S

Attach GDB:

gdb-multiarch build/ticktos.elf

(gdb) target remote localhost:1234

(gdb) break kernel_main

(gdb) continue

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What's Next

• Virtual memory and paging
• printf and basic stdio-like functions
• Multitasking between dummy tasks
• Porting my mini shell into the kernel

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