Note: this article was written by Daniel Reinhold.
One of the features of modern operating systems is the ability to separate application code from the critical code that implements the core of the system. Regular applications run in user mode (often referred to as userland) which means that they cannot directly manipulate the vital system data structures. This makes everything much more stable -- buggy apps may crash and burn themselves, but they can't bring down the rest of the system.
The flipside to this protection is that userland code is walled off from the kernel code. This means, for example, that your application cannot directly call a kernel function. But the kernel implements many useful services that most apps would like to take advantage of. Indeed, that is one of the main purposes of the kernel -- to abstract all those icky underlying hardware details and provide a clean, consistent interface for applications. So how does all this useful interface ever get called and used?
Intro Recently, David Reid reported that the OpenBeOS kernel source tree had been amended to fit its new environment after forking from NewOS. The jam scripts had been written, tweaked, and tested, and the new kernel was now capable of being built. He even included a picture of his computer booting from the freshly created floppy.
While I was happy to report this, I hadn't actually tried to do a build myself.
BodyI had a lot of company this weekend — it was really our first time entertaining in the new house (other than an occasional friend dropping by). I like to think that my friends are a fairly intelligent group. Birds of a feather and all. My friends often come to me for help with their computer "issues", despite the fact that I haven't run Windows as my OS of choice since 1996.
BodyDevice drivers are difficult to write. Understanding the hardware can be the hardest part. Often the documentation is hard to read and understand because it is written from a hardware designer's perspective (that is, if you can get the documentation -- many manufacturers are very reluctant to give it out). Drivers work directly with the kernel - a bad pointer can crash the whole OS. And, finally, you can't use warm and comfortable debugging tools, since you are working in the kernel.
