vmartinv/nek

Source: https://github.com/vmartinv/nek

Introduction

Nintendo Entertainment Kernel is a very basic kernel with only the minimun to run a NES emulator. This means that it can be run without any OS. It does not have pagging nor userspace nor any kind of protection at all. Only one program can be run. It is embedded in the kernel, which means the program’s code is compiled alongside the kernel.

Screenshots

Building

You should use make and provide the cross compiler:

PATH=/path/to/crosscompiler/bin:$PATH make kernel program=emulador

If there are not errors, kernel.elf should be in the bin folder.

Examples

Besides “emulador” there are three other working programs:

• mandelbrot (shows a explorable fractal)
• paleta (shows nes avalaible colors)
• corazon (a heart animation using math functions)

All of them can be compiled with the kernel using make.

Ej: make program=examples/mandelbrot

Installing

You may copy kernel.elf to /boot/ and add an entry at /etc/grub.d/40_custom like:

menuentry “nek” {

multiboot /boot/kernel.elf module /boot/initrd.img

}

Remember to update the config file:

sudo grub-mkconfig -o /boot/grub/grub.cfg

Testing

The makefile should run QEMU using the disk image disk.img. A loop device to this file must have been set up in the mount folder.

Dependencies

• i686 cross compiler (both C and ASM), like GCC and nasm
• GRUB2(optional): Generates .iso (cd image)
• QEMU(optional): Emulation
• Doxygen and Graphviz (optional): For generating the documentation
• grub-mkrescue (optional): For generating a booteable cd image (.iso)

Boot call stack

GRUB (multiboot standard)

kernel/arch/x86/init/boot.s <– calls c code, initializes stack

kernel_entry() at kernel/arch/x86/init/kernel_entry.c <–base system initilization

kmain() at kernel/kmain.c <— some services are started

main() at program/main.(c|cpp) <— main program

Folder Structure

• kernel folder has all related to the kernel
• kernel/arch code that depends on the architecture
• kernel/fs file system(currently only vfs implemented)
• fdlibm: a math library downloaded from internet
• util/specs: Some useful documents
• informe: University report (in spanish)
• iso: a few files to generate an .iso with the kernel
• util: contains the program to generate the initrd and a few other things
• util/fuente: Tools/file used to generate the console font