Valhalla

A basic proof-of-concept kernel written in Crystal.

Prerequisites

In order to build the kernel, a number of prerequisites are required:

• Crystal (0.10.0 onwards): Required to build the majority of the code. The code is largely limited to newer versions of Crystal, so more recent versions are preferred.
• nasm: Required for building the assembly code, where appropriate.
• i686-elf-ld: Required for linking together the resulting object files. As we're cross-compiling, life is much easier with a platform-appropriate linker. Such a linker can be built using the binutils section of the following guide: http://wiki.osdev.org/GCC_Cross-Compiler#The_Build
• grub-mkrescue: Required to build an ISO with GRUB2 pre-installed
• qemu(-system-i386): Optional: used to run the ISO, as through the run script

Building

For now, simply run ./make after the prerequisites have been installed. This will do a number of things:

1. Make a build folder.
2. Build all of the required assembly files.
3. Build all of the Crystal files.
4. Link together the object files to produce valhalla.bin.
5. Extract the symbols from valhalla.bin into valhalla.sym, and then strip valhalla.bin of its symbols.
6. Build vfs_make.
7. Build the VFS module using vfs_make from the contents of the vfs folder.
8. Assemble a boot disk, then use grub-mkrescue to create an ISO image with GRUB2 pre-installed.

Running

A ./run script has been provided for emulation use which assumes qemu-system-i386 is available.

To run the OS for testing, use ./run. To run the OS for debugging, use ./run debug, which allows the use of the GDB remote bridge.