We are developing an operating system for my personal research and practical education. For the academic purpose, this motivation is similar to MINIX, but we do not focus on theories. Our main objective is to provide knowledges on hardware-related programming. This is one of the most difficult and complex parts when we start the development of operating system from scratch.
The source code is available at the public github repository.
Now we have got into the 64-bit long mode kernel in C. As the first step of the kernel, we configure the global descriptor table (GDT) and interrupt descriptor table (IDT). GDT was already once configured just before entering 32 bit mode, but they are temporary ones and they did not support ring protection of CPUs. In this checkpoint, we prepare four sets of GDT entries for ring 0 to 3.