limine-c-template

Limine C Template

This repository will demonstrate how to set up a basic kernel in C using Limine.

How to use this?

Dependencies

Any make command depends on GNU make (gmake) and is expected to be run using it. This usually means using make on most GNU/Linux distros, or gmake on other non-GNU systems.

It is recommended to build this project using a standard UNIX-like system, using a Clang/LLVM toolchain capable of cross compilation.

Building also requires git, used to fetch the kernel’s dependencies (see kernel/get-deps), curl, used to download the Limine release and the EDK2 OVMF firmware images, and a C compiler for the host (cc by default, see the HOST_CC make variable), used to build the limine host utility.

Additionally, building an ISO with make all requires xorriso, and building a HDD/USB image with make all-hdd requires sgdisk (usually from gdisk or gptfdisk packages) and mtools.

Assembly files with the *.S extension are built using the same toolchain as the C sources. Only *.asm files, which are built for x86_64 alone and of which the template ships none, require nasm. The run targets require qemu.

Toolchain selection

The TOOLCHAIN and TOOLCHAIN_PREFIX make variables can be used to set the toolchain. TOOLCHAIN can be set to llvm to use Clang/LLVM.

For example:

make TOOLCHAIN=llvm

or:

make TOOLCHAIN_PREFIX=x86_64-elf-

The kernel is linked through the compiler driver, using its default linker for GCC and LLD for Clang. A different linker can be picked by adding a -fuse-ld= option to LDFLAGS.

Link-time optimisation can be enabled by adding -flto to CFLAGS, for example:

make CFLAGS='-g -O2 -pipe -flto'

Architectural targets

The ARCH make variable determines the target architecture to build the kernel and image for.

The default ARCH is x86_64. Other options include: aarch64, loongarch64, and riscv64.

Makefile targets

Running make all will compile the kernel (from the kernel/ directory) and then generate a bootable ISO image.

Running make all-hdd will compile the kernel and then generate a raw image suitable to be flashed onto a USB stick or hard drive/SSD.

Running make run will build the kernel and a bootable ISO (equivalent to make all) and then run it using qemu (if installed).

Running make run-hdd will build the kernel and a raw HDD image (equivalent to make all-hdd) and then run it using qemu (if installed).

For x86_64, the run-bios and run-hdd-bios targets are equivalent to their non -bios counterparts except that they boot qemu using the default SeaBIOS firmware instead of OVMF.