Our Approach

This book introduces the reader to the concepts necessary to understand the kernel. We follow a top-down approach in the following two ways:

First, we associate the kernel workings with the execution of user space operations the reader may be more familiar with and strive to explain the kernel workings in association with this. When possible, we begin with a user space example and trace the execution of the code down into the kernel. It is not always possible to follow this tracing straight down since the subsystem data types and substructures need to be introduced before the explanation of how it works can take place. In these cases, we tie in explanations of the kernel subsystem with specific examples of how it relates to a user space program. The intent is twofold: to highlight the layering seen in the kernel as it interfaces with user space on one side and the hardware on the other, and to explain workings of the subsystem by tracing the code and following the order of events as they occur. We believe this will help the reader get a sense of how the kernel workings fit in with what he knows, and will provide him with a framed reference for how a particular functionality associates to the rest of the operating system.

Second, we use the top-down perspective to view the data structures central to the operation of the subsystem and see how they relate to the execution of the system's management. We strive to delineate structures central to the subsystem operation and to keep focus on them as we follow the operation of the subsystem.