Singh - Mac OS X internals: a systems approach

A Systems Approach

Amit Singh

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Library of Congress Cataloging-in-Publication Data

Singh, Amit.
Mac OS X internals : a systems approach / Amit Singh.
p. cm.
Includes bibliographical references and index.
ISBN 0-321-27854-2 (hardback : alk. paper)
1. Mac OS. 2. Operating systems (Computers) 3. Macintosh (Computer)--Programming. I. Title.
QA76.76.O63S5645 2006
005.4'4682dc22
2006014901

Copyright 2007 Pearson Education, Inc.

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ISBN 0-321-27854-2

Text printed in the United States on recycled paper at Courier in Westford, Massachusetts.

First printing, June 2006

To my parents, Sharda and Amar Singh, for teaching me everything I know about learning, for giving me everything that I ever needed (or wanted) from them, and for always being in my way without becoming an obstacle.

Although Mac OS X is a relatively new operating system, its lineage is rather colorful, and the history of most of its components is much older. Mac OS X, and Apple in general, has attracted a lot of attention in recent years. Given Apples cult-like status, and the unique cultural and technical composition of Mac OS X, it is not surprising that people with vastly different backgrounds and interestsboth users and non-users of Mac OS Xare curious about the system.

After working on, programming on, and extending several operating systems over the years, I was introduced to Mac OS X on April 1, 2003.Mac OS X. Consequently, the system is often misunderstood because of long-standing myths and stereotypes, or is perceived as a black box.

The purpose of this book is to deconstruct and demystify Mac OS X by describing it from a system-design perspective. It takes an implementation-oriented approach to understanding the system. Consider the example of interprocess communication (IPC). Mac OS X has numerous user-level and kernel-level IPC mechanisms, some of which are well known and documented. Rather than just showing how to use these mechanisms, the book explains the design and implementation of the most fundamental mechanism (Mach IPC), and then discusses how the other mechanisms are layered on top of one another. My goal is not to teach you how to do something specificmy goal is to provide you with enough knowledge and examples so that after reading the book, depending on your interests and background, you can build upon your newly gained knowledge and do what you choose.

Along with text, the book uses detailed illustrations, function call graphs, annotated code excerpts, and programming examples to present a detailed examination of Mac OS X. To keep the subject matter interesting and accessibleeven to the casual readerthe book contains relevant trivia, digressions, and other tidbits.

I hope the book will be useful to anyone curious about the composition and working of Mac OS X.

Application programmers can gain a deeper understanding of how their applications interact with the system. System programmers can use the book as a reference and to construct a better picture of how the core system works. In my experience as a programmer, a solid understanding of system internals is immensely useful in design, development, and debugging. For example, you know what the system is capable of, what is feasible and what is not, what the best option is in a given situation, and what the plausible reasons are for certain program behavior. This books primary goal is to build a strong foundation for anyone who programs on Mac OS X.

Mac OS X users can read the book to better understand how the system is designed and how it comes together. System administrators and technical support staff will also find value in the book.

Besides those who use Mac OS X, the intended audience includes members of other technical communities, such as the BSD, Linux, and Windows communities. Given that many internal aspects of Mac OS X are radically different from these systems (for example, how the Mach kernel is used), the book will help such readers broaden their knowledge, and will assist them in comparing and contrasting Mac OS X with other operating systems.

The book will also be useful in an advanced operating systems course, particularly if you wish to do a case study on Mac OS X. The book is not suitable, however, as an introductory text. Most of the material is not presented at an introductory level, although I introduce many of the advanced topics with at least some background information.

Modern operating systems have become so large and complex that it is impossible to reasonably describe an entire system in a book. This book is somewhat ambitious in that it attempts to cover Mac OS X in substantial breadth and depth. The most important contributors to the books depth are the carefully selected programming examples. The book is organized into twelve chapters. Although much of the books content is rather technical, each chapter has sections that should be accessible to non-programmers.

, which covers all of Apples past and present operating systems, is available on this books accompanying web site.

, An Overview of Mac OS X, is an eclectic tour of Mac OS X and its important features. It contains brief overviews of various layers that constitute the system.

, Inside an Apple, describes the PowerPC architecture, using the PowerPC 970 (G5) processor line as a specific example. It also discusses the PowerPC assembly language and calling conventions.

, The Firmware and the Bootloader, describes both Open Firmware and the Extensible Firmware Interface (EFI), along with their respective bootloaders. It discusses the roles the firmware and the bootloader play in the systems operation, usage scenarios, and events that occur during early bootstrapping.