Kernel OS

A minimal 64-bit x86 bare-metal kernel built from scratch, featuring a custom cross-compilation toolchain, VGA text output, and GRUB multiboot support.

Source code and builds hosted at abhishekprajapatt/kernel-os.

Features

• Custom x86_64-elf toolchain with multilib (32/64-bit support) built via Docker.
• VGA text mode printing (yellow "Welcome!" message on boot).
• Long-mode entry with basic paging and GDT setup.
• Bootable GRUB ISO for QEMU emulation.

Prerequisites

• A text editor such as VS Code.
• Docker for creating the build environment.
• QEMU for emulating the kernel (add to PATH if needed).

Setup

Build the toolchain and environment image:

• docker build -f src/Dockerfile -t kernel-os .

Build

Enter the build environment (mounts your project dir):

• Linux or macOS: docker run --rm -it -v "$(pwd)":/root/env kernel-os
• Windows (CMD): docker run --rm -it -v "%cd%":/root/env kernel-os
• Windows (PowerShell): docker run --rm -it -v "${PWD}:/root/env" kernel-os
• Note: Use the Linux command for WSL, MSYS2, or Git Bash. Ensure Docker has access to your project drive (Settings > Resources > File Sharing in Docker Desktop).

Inside the container, build the kernel:

• make all (sets up ISO, compiles sources, links kernel.bin).

Exit with exit. Outputs: dist/x86_64/kernel.iso.

Emulate

Run in QEMU (from host, after building):

• make run (uses qemu-system-x86_64 -cdrom dist/x86_64/kernel.iso -serial stdio).

Direct QEMU command:

• qemu-system-x86_64 -cdrom dist/x86_64/kernel.iso

If boot fails (e.g., BIOS issues):

• Windows: qemu-system-x86_64 -cdrom dist/x86_64/kernel.iso -L "C:\Program Files\qemu"
• Linux: qemu-system-x86_64 -cdrom dist/x86_64/kernel.iso -L /usr/share/qemu/

For USB boot: Copy ISO to a bootable drive (unverified).

Cleanup

Remove build artifacts:

• make clean

Remove Docker image:

• docker rmi kernel-os -f

Project Structure

• src/: Toolchain scripts (build-binutils.sh, build-gcc.sh) and Dockerfile.
• buildenv/: GCC multilib patch and config.
• src/impl/: Kernel sources (kernel/ for core C, x86_64/ for arch asm/C, intf/ for headers).
• targets/x86_64/: Linker script and ISO template.
• Makefile: Builds objects, links, generates ISO.

Troubleshooting

• Toolchain errors: Rebuild Docker image; ensure GMP/MPFR prereqs (handled in Dockerfile).
• QEMU no output: Add -d cpu for debug; check multiboot header in header.asm.
• Multilib: Verified with x86_64-elf-gcc -m32 -v.

Contributions welcome! Fork and PR to abhishekprajapatt/kernel-os.