Tilck: a tiny Linux-compatible kernel

Tilck is an educational monolithic kernel designed to be Linux-compatible at binary level. It runs on i686 and RISCV64 at the moment. Project’s small-scale and simple design makes it the perfect playground for playing in kernel mode while retaining the ability to compare how the very same usermode bits run on the Linux kernel as well. That’s a rare feature in the realm of educational kernels. Because of that, building a program for Tilck requires just a gcc-musl toolchain from bootlin.com. Tilck has no need to have its own set of custom written applications, like most educational kernels do. It just runs mainstream Linux programs like the BusyBox suite. While the Linux-compatibility and the monolithic design might seem a limitation from the OS research point of view, on the other side, such design bring the whole project much closer to real-world applications in the future, compared to the case where some serious (or huge) effort is required to port pre-existing software on it. Also, nothing stops Tilck from implementing custom non-Linux syscalls that aware apps might take advantage of.
↫ Tilck GitHub page

Tilck implements about 100 Linux syscalls, and is not focused on replacing the Linux kernel or even becoming a generic desktop or server operating system. It supports both i686 and RISC-V, has support for FAT, and a whole slew of other features. It can run a number of console and even a few framebuffer applications, but don’t expect things like X11 to work, or to ever work.