Name		Name	Last commit message	Last commit date
.github/ISSUE_TEMPLATE		.github/ISSUE_TEMPLATE
cpu		cpu
drivers		drivers
fs		fs
init		init
kernel		kernel
libc		libc
memory		memory
.gitignore		.gitignore
.prettierrc		.prettierrc
LICENSE		LICENSE
Makefile		Makefile
README.md		README.md
Resources.md		Resources.md
boot.asm		boot.asm
cross-compiler.sh		cross-compiler.sh
get_kernel_size		get_kernel_size
linker.ld		linker.ld
make_initrd.c		make_initrd.c

Repository files navigation

Create an OS from scratch

I have always wanted to boot OS from scratch.
In this project we are bootstraping kernel via a simple boot sector which loads the kernel into memory and switches to 32-bit protected mode from 16-bit real mode and then calls the kernel code.
Kernel sets up the global descriptor table, interrupt descriptor table, initializes timer, keyboard interrupt and paging.

Things which are done

Boot from scratch
Enter 32-bit Protected mode
Jump from assembly to C
Interrupt handling
Keyboard input and output
A basic libc
Virtual memory (Paging)
Ordered array data structure
Memory Manager
Basic shell commands
Multiboot compliant kernel

Directory structure

├── boot
│   ├── boot_sect.asm
│   ├── disk_load.asm
│   ├── gdt.asm
│   ├── print_hex.asm
│   ├── print_string.asm
│   ├── print_string_pm.asm
│   └── switch_to_pm.asm
├── cpu
│   ├── idt.c
│   ├── idt.h
│   ├── interrupt.asm
│   ├── isr.c
│   ├── isr.h
│   ├── ports.c
│   ├── ports.h
│   ├── timer.c
│   ├── timer.h
│   └── types.h
├── cross-compiler.sh
├── drivers
│   ├── keyboard.c
│   ├── keyboard.h
│   ├── screen.c
│   └── screen.h
├── get_kernel_size
├── kernel
│   ├── bootanimation.c
│   ├── bootanimation.h
│   ├── kernel.c
│   ├── kernel_entry.asm
│   ├── kernel.h
│   ├── kshell.c
│   └── kshell.h
├── libc
│   ├── function.c
│   ├── function.h
│   ├── mem.c
│   ├── mem.h
│   ├── ordered_array.c
│   ├── ordered_array.h
│   ├── string.c
│   └── string.h
├── LICENSE
├── linker.ld
├── Makefile
├── memory
│   ├── kheap.c
│   ├── kheap.h
│   ├── paging.c
│   └── paging.h
├── README.md
└── Resources.md

Build

$ sudo apt install nasm     		# Netwide Assembler
$ sudo apt install qemu-system-x86 	# CPU emulator
$ sudo apt install make     		# Build system
$ ./cross-compiler          		# Builds the cross compiler
$ make run                  		# Build and Run