An operating system written in C17 (gnu17), for x86_64, aarch64, and riscv64. loongarch64 is being worked on but isn't currently functional.

x86_64 is the most feature complete, while aarch64 and riscv64 are catching up

Migrated from older repository: https://github.com/suhas-pai/operating-system-old Check older repository for full commit history

The project has the implemented all of the following:

• Has serial UART drivers; uart8250 on x86_64, riscv64 and pl011 on aarch64
• Full abstract virtual memory manager with large page support.
• Implements kmalloc() using a slab allocator.
• Keeps time with RTC (google,goldfish-rtc on riscv64) and Local-APIC Timer, HPET on x86_64
• Discovers devices in ACPI Tables and Device Tree (when available)
• Finds and Initializes PCI(e) Devices.

And more

The following is currently being thought out and worked on.

• IDE, AHCI, SATA, NVME controllers to read disks
• VirtIO drivers
• Virtual File System (VFS)
• Full SMP support with scheduler
• User processes and threads

LLVM/Clang are recommended as the toolchain and compiler to build this project, GCC will likely be able to build this project. These instructions will build with LLVM/Clang

The kernel GitHub Workflow follows the steps detailed below on both macOS and Ubuntu (Linux) to build this project.

Run the following command to install the required packages from Homebrew.

brew install llvm make nasm xorriso coreutils mtools gptfdisk lld

Note that mtools and gptfdisk are only required to build the hdd targets.

Per the installation instructions of llvm, make, and coreutils, add the following paths to your $PATH environment variable:

/opt/homebrew/opt/llvm/bin
/opt/homebrew/opt/make/libexec/gnubin
/usr/local/opt/coreutils/libexec/gnubin

Install the latest version of LLVM available. The best option is from llvm.org. The llvm version available in your system's package manager may be too old to build this project.

This project also requires installing nasm, xorriso, sgdisk, and mtools. Make sure to add llvm's installation folder to your $PATH environment variable.

Note that mtools are only required to build the hdd targets. sgdisk is only required to build x86_64 and hdd targets

The GNUmakefile provides the following targets to use with make for building:

• all target builds the system for the given architecture in ARCH, creating a bootable .iso image containing the built system.
• all-hdd target builds a flat hard disk/USB image instead.
• install target can install the system into a directory provided by the variable DESTDIR.

Several variables are available to configure how the project is built:

• ARCH= specifies the architecture the project is built for. Default is x86_64, but also accepts aarch64, riscv64, loongarch64 as inputs to run the project on the respective architecture.
• CC=, LD= detail the compiler and linker used to build the kernel. Default is CC=cc LD=ld, though these are unlikely to be able to build this project.

This project uses the Makefile build system. To run the project (In QEMU), use the following command:

make run ARCH=x86_64 CC=clang LD=ld.lld

To run from a built raw HDD image (creating if necessary), rather than a bootable ISO, run the following command instead:

make run-hdd ARCH=x86_64 CC=clang LD=ld.lld

On x86_64, additional options are available:

• run-bios, run-hdd-bios Makefile targets are equivalent to their non -bios counterparts except that they boot QEMU using the default SeaBIOS firmware instead of OVMF.

Several variables are also available to configure the system provided by QEMU. If not provided, they are given a default value that is detailed below:

• MEM= to configure memory size (in QEMU units). Default is 4G
• SMP= to configure amount of cpus. Default is 4
• DEBUG= to build in debug mode and to start in QEMU in debugger mode. Default is 0
• RELEASE= to build in release mode with full optimizations (though ubsan is still enabled). Default is 0
• CONSOLE= to start in QEMU's console mode. Default is 0
• DISABLE_ACPI= to start QEMU's machine without ACPI, relying exclusively on the DTB (Flattened Device Tree). Default is 0
• DISABLE_FLANTERM= to disable flanterm, the terminal emulator used in this project. This option helps improve bootup performance. Default is 0
• DRIVE_KIND= to specify what drives are available from QEMU. Default is scsi for riscv64, and nvme for all other archs. Available options are:
  • block which provides the default cdrom/hda access from QEMU
  • scsi which provides VirtIO to access drives through the virtio-scsi interface
  • nvme which provides nvme drives instead
• NVME_MAX_QUEUE_COUNT= to set nvme's max queue count. Only available when DRIVE_KIND is nvme. Default is 64
• TRACE= to trace certain logs in qemu to log.txt. Takes a space separated string and provides qemu with the list in the correct format. Default is ""
• CHECK_SLABS= to enable pervasive slab checks in kmalloc() and other slab allocators. Default is 0
• DEBUG_LOCKS= to enable pervasive lock integrity checks. Default is 0
• CONFIG_UACPI= to use uACPI, an implementation of ACPI necessary for full device driver and hardware support. Default is 1