eshcoreos

A hobbyist OS built for understanding

About

As a sophomore computer science student, I felt an urge to understand some of the more low-level things that our systems do. There's no better way to understand exactly what things do than to build them, so I decided that in pursuit of an understanding of exactly how operating systems work, I'd implement my own. I also decided to record the things I learned along the way—check out the devlog.md file!

The operating system itself is designed to run in QEMU and currently combines an x86 bootloader, a small protected-mode C kernel, VGA text output, CPU exception handling, remapped hardware IRQs, and a PIT-based timer tick.

Requirements

To build eshcoreos, you'll need the following:

• nasm (the Netwide Assembler), to assemble the bootloader
• make, to run the build automation
• qemu, to emulate the system
• a bare-metal C compiler targeting i386-elf (or similar)—I use x86_64-elf-gcc on macOS.

You can install these easily on macOS (with Homebrew) or Linux (with APT):

# macOS, using Homebrew
brew update && brew upgrade
brew install nasm qemu
brew tap nativeos/i386-elf-toolchain
brew install x86_64-elf-binutils x86_64-elf-gcc

# Ubuntu/Debian Linux
sudo apt install nasm qemu make gcc gcc-i386-elf

Note: Depending on which compiler you use, you'll need to update the Makefile so that it runs your compiler.

Build & Run

To build eshcoreos and run it in QEMU:

make
make run

Build artifacts are written to build/, including the final disk image at build/os-image.bin.

Project Layout

• boot/: 16-bit bootloader code that loads the kernel and enters protected mode
• kernel/: freestanding C and assembly kernel code
• docs/: development checklist and learning log
• build/: generated object files, kernel binaries, and disk image

Current Status

eshcoreos currently boots into 32-bit protected mode, writes to VGA text memory, installs an IDT for CPU exceptions and hardware IRQs, remaps the PIC, programs the PIT at 100 Hz, and prints a simple timer heartbeat from IRQ0.

About Me

My name is Jackson Eshbaugh, and I'm a passionate student researcher studying computer science and French at Lafayette College. It is my goal to join academia and contribute to the conversation of science while inspiring and guiding future students through the wonderful world of computer science. You can read more about me, my research interests, and my work on my website.