HmmOS

Second attempt at writing an OS, this time a little more from scratch now that I have a slightly better idea of what the bootloader does.

Focusing on x86 first, will maybe update this to be for x86_64 later.

High-level roadmap for HmmOS:

• Bootloader
  • Simple boot protocol with bootloader requests
  • Kernel loader
    • With FAT32 support
    • With ELF support
• Memory management
  • Page frame allocator
  • Slab allocator
  • vmalloc
• Userspace processes
  • Kernel threads
  • Thread scheduling
  • ELF loader
  • Syscalls
  • Shared libraries
  • Sample programs
    • Shell
    • Simple libc implementation
• Filesystem
  • Filesystem drivers
    • FAT32
    • ext2
  • VFS layer
• Device drivers (very simple)
  • Serial port
  • BIOS text mode display
  • ACPI
  • Keyboard
  • AHCI (SATA)
  • Graphics
  • UDP
  • TCP
• SMP
  • Locking primitives
• Tooling
  • Debugging in GDB
  • clang+gcc tooling
  • Testing in QEMU w/ optional KVM virtualization
  • Unit test framework
  • Kernel module system with dependencies

Setup

This project is mainly built with clang/LLVM toolchains in mind. This includes clang, lld, clangd, and clang-format. You'll need at least version 14.

GNU binutils is needed where LLVM is lacking (i.e. as for GNU AT&T asm syntax + objdump and friends). GNU mtools is also required to build the binary.

This will be tested with qemu with QEMU and KVM emulation.

Versions:

$ as --version
GNU assembler (GNU Binutils for Debian) 2.40
Copyright (C) 2023 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or later.
This program has absolutely no warranty.
This assembler was configured for a target of `x86_64-linux-gnu'.
$
$ clang --version
Debian clang version 14.0.6
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
$
$ qemu-system-i386 --version
QEMU emulator version 7.2.13 (Debian 1:7.2+dfsg-7+deb12u7)
Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project developers
$
$ mtools --version
mtools (GNU mtools) 4.0.32
configured with the following options: enable-xdf disable-vold disable-new-vold disable-debug enable-raw-term
$
$ uname -a
Linux jebian 6.1.0-27-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.115-1 (2024-11-01) x86_64 GNU/Linux

Getting started

Build the bootloader and run it in QEMU. Make sure to have qemu and GNU make installed, and doxygen if you want to generate documentation.

$ # Run the kernel
$ make run
$
$ # Run tests
$ make run TEST=all
$ make run TEST=<testselection>
$
$ # Generate documentation
$ make docs

Debugging in GDB

$ # Compile with debug symbols enabled and start running in QEMU.
$ # This doesn't actually start until `make gdb` is called.
$ make runi
$
$ # Start gdb and connect to the previous session, loading the debug
$ # symbols compiled from the last run to `make runi`. Make sure to
$ # run this with the same compile options (e.g., OPT=*, DEBUG=*) as
$ # in `make runi`.
$ make gdb

Misc.

Name courtesy of @Victoooooor.