Nufflee/EPIC

Tiny kernel experiment with the goal of running a precompiled 32-bit Linux ELF executable of `echo` as-is.

EPIC

EPIC is a small kernel/OS experiment with the goal of running a precompiled 32-bit Linux ELF executable of echo to learn what it takes to do that.

The kernel can currently only run in 32-bit protected mode on x86 (i386) machines.

Development is streamed on my Twitch channel.

Features

• Simple memory management (physical page allocator and malloc)
• Serial port output
• VGA text mode driver
• Basic interrupt-driven keyboard driver
• Simple terminal emulator
• ATA hard drive driver
• Custom read-only file system - EPICFS
• Linux-compatible syscalls
• Flat and ELF32 binary execution
• Simple C program support

Resources used

• OSDev Wiki - Tons of tutorials about anything OS Dev related
• JamesM's kernel development tutorials - This tutorial has some known issues.
• Linux x86 Syscall Reference
• x86 ISA Reference
• And others...

Building

(Note: this also works perfectly on Ubuntu WSL with an X Server for QEMU)

Cloning

You have to clone this repository recursively because there are submodules:

git clone --recurse-submodules https://github.com/Nufflee/epic

Dependencies

• git
• i686 gcc8
• nasm
• make
• python3 (for mkfs.epic tool that generates an EPICFS image)
• qemu (for testing and debugging)
• xorriso (optional, only needed for ISO creation)

sudo apt install git gcc-8-i686-linux-gnu nasm make python3 qemu xorriso # Ubuntu/Debian
                                                                         # Feel free to add dependency instructions for your distro/OS

Building

Compile epic-musl:

bash ./tools/build_musl.sh

In case you want to rebuild epic-musl, you have to clean it up first:

bash ./tools/build_musl.sh clean

Build the kernel itself:

make build

Or build the kernel and then create a full .iso disk image (xorriso is needed for this to succeed):

make iso

Running

There are a couple of different options to test run using qemu you can either build and run the kernel directly by using:

make run

Alternatively you can build a full cd disk image and run qemu off of that using:

make run_iso

Debugging

Running the kernel in a debugger (gdb) can be done using:

make debug