This book targets software developers who are interested in understanding the Linux kernel. It is not a line-by-line commentary of the kernel source. Nor is it a guide to developing drivers or a reference on the kernel API (as if there even were a formal kernel APIhah!). Instead, the goal of this book is to provide enough information on the design and implementation of the Linux kernel that a sufficiently accomplished programmer can begin developing code in the kernel. Kernel development can be fun and rewarding, and I want to introduce the reader to that world as readily as possible. This book, however, in discussing both theory and application, should appeal to readers of either interest. I have always been of the mind that one needs to understand the theory to understand the application, but I do not feel that this book leans too far in either direction. I hope that whatever your motivations for understanding the Linux kernel, this book will explain the design and implementation sufficiently for your needs.
Thus, this book covers both the usage of core kernel systems and their design and implementation. I think this is important, and deserves a moment's discussion. A good example is Chapter 7, "Bottom Halves and Deferring Work," which covers bottom halves. In that chapter, I discuss both the design and implementation of the kernel's bottom-half mechanisms (which a core kernel developer might find interesting) and how to actually use the exported interfaces to implement your own bottom half (which a device driver developer might find interesting). In fact, I believe both parties should find both discussions relevant. The core kernel developer, who certainly needs to understand the inner workings of the kernel, should have a good understanding of how the interfaces are actually used. At the same time, a device driver writer will benefit from a good understanding of the implementation behind the interface.
This is akin to learning some library's API versus studying the actual implementation of the library. At first glance, an application programmer needs only to understand the APIit is often taught to treat interfaces as a black box, in fact. Likewise, a library developer is concerned only with the library's design and implementation. I believe, however, both parties should invest time in learning the other half. An application programmer who better understands the underlying operating system can make much greater use of it. Similarly, the library developer should not grow out of touch with the reality and practicality of the applications that use the library. Consequently, I discuss both the design and usage of kernel subsystems, not only in hopes that this book will be useful to either party, but also in hopes that the whole book is useful to both parties.
I assume that the reader knows the C programming language and is familiar with Linux. Some experience with operating system design and related computer science concepts is beneficial, but I try to explain concepts as much as possibleif not, there are some excellent books on operating system design referenced in the bibliography.
This book is appropriate for an undergraduate course introducing operating system design as the applied text if an introductory book on theory accompanies it. It should fare well either in an advanced undergraduate course or in a graduate-level course without ancillary material. I encourage potential instructors to contact me; I am eager to help.