Startup

On startup, the first thing that happens is that the BIOS of your computer loads Limine, the bootloader that Cosmos uses. From there, there is some hand-coded assembly that runs before the "Cosmos layer" kicks in. From there, the IL2CPU-ed C# entry point Cosmos.System.Kernel.Start() or Sys.Kernel.Start() is called.

By the way, Cosmos.System.Kernel is an abstract class that forms the Cosmos framework. It provides a base that your OS is built on top of.

Sys.Kernel.Start()

What does it do?

Kernel.Start() does quite a bit of stuff. First, it checks if System.String.Empty is null. If it is null, then it will just throw an exception. If it isn't, it just continues. After that check, Kernel.Start() initializes the hardware bootstrap, then calls OnBoot().

The next article explains what OnBoot() is.

Then, Kernel.Start() calls your BeforeRun() method, after it finishes, Kernel.Start() enables the hardware interrupts. Then it simply does a while (!mStopped) loop with your Run() method. After that, it calls an optional method called AfterRun(). By default, AfterRun() is just empty, so don't worry about nulls or something like that. Then it finishes. All of that is also try/catched too with the A kernel exception has occurred message.

Overriding it

You can override the Kernel.Start() method in your Kernel to suppress the standard Cosmos boot routines and get deeper control of Cosmos.

You override it the same way you do with other methods. An extremely simple base override in your Kernel would be: protected override void Start() {}

The default Kernel.Start() method is located in Cosmos\source\Cosmos.System2\Kernel.cs. You can copy it and make modifications with your Kernel override.

Last updated on 20 May 2023.