Design and Implementation of the FreeBSD Operating System, The

Marshall Kirk McKusick writes books and articles, consults, and teaches classes on UNIX- and BSD-related subjects. While at the University of California at Berkeley, he implemented the 4.2BSD fast filesystem and was the Research Computer Scientist at the Berkeley Computer Systems Research Group (CSRG), overseeing the development and release of 4.3BSD and 4.4BSD. His particular areas of interest are the virtual-memory system and the filesystem. He earned his undergraduate degree in electrical engineering from Cornell University and did his graduate work at the University of California at Berkeley, where he received master's degrees in computer science and business administration and a doctoral degree in computer science. He has twice been president of the board of the Usenix Association, is currently a member of the FreeBSD Foundation Board of Directors, a member of the editorial board of ACM's Queue magazine, a senior member of the IEEE, and a member of the Usenix Association, ACM, and AAAS. In his spare time, he enjoys swimming, scuba diving, and wine collecting. The wine is stored in a specially constructed wine cellar in the basement of the house that he shares with Eric Allman, his partner of 35-and-some-odd years and husband since 2013. George V. Neville-Neil hacks, writes, teaches, and consults in the areas of security, networking, and operating systems. Other areas of interest include embedded and real time systems, network time protocols, and code spelunking. In 2007 he helped start the AsiaBSDCon series of conferences in Tokyo, Japan, and has served on the program committee every year since then. He is a member of the FreeBSD Foundation Board of Directors, and was a member of the FreeBSD Core Team for four years. Contributing broadly to open source, he is the lead developer on the Precision Time Protocol project and the developer of the Packet Construction Set. Since 2004 he has written a monthly column, Kode Vicious, that appears both in ACM's Queue and Communications of the ACM. He serves on the editorial board of ACM's Queue magazine, is vice chair of ACM's Practitioner Board and is a member of the Usenix Association, ACM, IEEE, and AAAS. He earned his bachelor's degree in computer science at Northeastern University in Boston, Massachusetts. He is an avid bicyclist, hiker, and traveler, who has lived in Amsterdam, The Netherlands, and Tokyo, Japan. He is currently based in Brooklyn, New York, where he lives with his husband, Kaz Senju. Robert N. M. Watson is a university lecturer in systems, security, and architecture in the Security Research Group at the University of Cambridge Computer Laboratory. He supervises doctoral students and postdoctoral researchers in cross-layer research projects spanning computer architecture, compilers, program analysis, program transformation, operating systems, networking, and security. Dr. Watson is a member of the FreeBSD Foundation Board of Directors, was a member of the FreeBSD Core Team for ten years, and has been a FreeBSD committer for fifteen years. His open-source contributions include work on FreeBSD networking, security, and multiprocessing. Having grown up in Washington, D. C., he earned his undergraduate degree in logic and computation, with a double major in computer science, at Carnegie Mellon University in Pittsburgh, Pennsylvania, and then worked at a series of industrial research labs investigating computer security. He earned his doctoral degree at the University of Cambridge, where his graduate research was in extensible operating-system access control. Dr. Watson and his wife, Dr. Leigh Denault, have lived in Cambridge, England for ten years.

Preface xxi

About the Authors xxix

Part I: Over view 1

Chapter 1: History and Goals 3

1.1 History of the UNIX System 3

1.2 BSD and Other Systems 7

1.3 The Transition of BSD to Open Source 9

1.4 The FreeBSD Development Model 14

References 17

Chapter 2: Design Overview of FreeBSD 21

2.1 FreeBSD Facilities and the Kernel 21

2.2 Kernel Organization 23

2.3 Kernel Services 26

2.4 Process Management 26

2.5 Security 29

2.6 Memory Management 36

2.7 I/O System Overview 39

2.8 Devices 44

2.9 The Fast Filesystem 45

2.10 The Zettabyte Filesystem 49

2.11 The Network Filesystem 50

2.12 Interprocess Communication 50

2.13 Network-Layer Protocols 51

2.14 Transport-Layer Protocols 52

2.15 System Startup and Shutdown 52

Exercises 54

References 54

Chapter 3: Kernel Services 57

3.1 Kernel Organization 57

3.2 System Calls 62

3.3 Traps and Interrupts 64

3.4 Clock Interrupts 65

3.5 Memory-Management Services 69

3.6 Timing Services 73

3.7 Resource Services 75

3.8 Kernel Tracing Facilities 77

Exercises 84

References 85

Part II: Processes 87

Chapter 4: Process Management 89

4.1 Introduction to Process Management 89

4.2 Process State 92

4.3 Context Switching 99

4.4 Thread Scheduling 114

4.5 Process Creation 126

4.6 Process Termination 128

4.7 Signals 129

4.8 Process Groups and Sessions 136

4.9 Process Debugging 142

Exercises 144

References 146

Chapter 5: Security 147

5.1 Operating-System Security 148

5.2 Security Model 149

5.3 Process Credentials 151

5.4 Users and Groups 154

5.5 Privilege Model 157

5.6 Interprocess Access Control 159

5.7 Discretionary Access Control 161

5.8 Capsicum Capability Model 174

5.9 Jails 180

5.10 Mandatory Access-Control Framework 184

5.11 Security Event Auditing 200

5.12 Cryptographic Services 206

5.13 GELI Full-Disk Encryption 212

Exercises 217

References 217

Chapter 6: Memory Management 221

6.1 Terminology 221

6.2 Overview of the FreeBSD Virtual-Memory System 227

6.3 Kernel Memory Management 230

6.4 Per-Process Resources 244

6.5 Shared Memory 250

6.6 Creation of a New Process 258

6.7 Execution of a File 262

6.8 Process Manipulation of Its Address Space 263

6.9 Termination of a Process 266

6.10 The Pager Interface 267

6.11 Paging 276

6.12 Page Replacement 289

6.13 Portability 298

Exercises 308

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