Embedded Linux Primer

Embedded Linux Primer

Up-to-the-Minute, Complete Guidance for Developing Embedded Solutions with Linux Linux has emerged as today's #1 operating system for embedded products. Christopher Hallinan's Embedded Linux Primer has proven itself as the definitive real-world guide to building efficient, high-value, embedded systems with Linux. Now, Hallinan has thoroughly updated this highly praised book for the newest Linux kernels, capabilities, tools, and hardware support, including advanced multicore processors. Drawing on more than a decade of embedded Linux experience, Hallinan helps you rapidly climb the learning curve, whether you're moving from legacy environments or you're new to embedded programming. Hallinan addresses today's most important development challenges and demonstrates how to solve the problems you're most likely to encounter. You'll learn how to build a modern, efficient embedded Linux development environment, and then utilize it as productively as possible. Hallinan offers up-to-date guidance on everything from kernel configuration and initialization to bootloaders, device drivers to file systems, and BusyBox utilities to real-time configuration and system analysis. This edition adds entirely new chapters on UDEV, USB, and open source build systems. * Tour the typical embedded system and development environment and understand its concepts and components. * Understand the Linux kernel and userspace initialization processes. * Preview bootloaders, with specific emphasis on U-Boot. * Configure the Memory Technology Devices (MTD) subsystem to interface with flash (and other) memory devices. * Make the most of BusyBox and latest open source development tools. * Learn from expanded and updated coverage of kernel debugging. * Build and analyze real-time systems with Linux. * Learn to configure device files and driver loading with UDEV. * Walk through detailed coverage of the USB subsystem. * Introduces the latest open source embedded Linux build systems. * Reference appendices include U-Boot and BusyBox commands.

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Christopher Hallinan is a technical marketing engineer for the Embedded Systems Division of Mentor Graphics, living and working in Florida. He has spent more than 25 years in the networking and communications industry, mostly in various product development, management, and marketing roles, where he developed a strong background in the space where hardware meets software. Prior to joining Mentor Graphics, he spent nearly seven years as a field applications engineer for Monta Vista Software. Before that, Hallinan spent four years as an independent Linux consultant, providing custom Linux board ports, device drivers, and bootloaders. His introduction to the open source community was through contributions to the popular U-Boot bootloader. When not messing about with Linux, he is often found singing and playing a Taylor or Martin.

Inhaltsangabe

Foreword for the First Edition
xxv
Foreword for the Second Edition
xxvi
Preface
xxvii
Acknowledgments for the First Edition
xxxiii
Acknowledgments for the Second Edition
xxxv
About the Author
xxxvi
Chapter 1 Introduction
1
1.1 Why Linux
2
1.2 Embedded Linux Today
3
1.3 Open Source and the GPL
3
1.3.1 Free Versus Freedom
4
1.4 Standards and Relevant Bodies
5
1.4.1 Linux Standard Base
5
1.4.2 Linux Foundation
6
1.4.3 Carrier-Grade Linux
6
1.4.4 Mobile Linux Initiative: Moblin
7
1.4.5 Service Availability Forum
7
1.5 Summary
8
1.5.1 Suggestions for Additional Reading
8
Chapter 2 The Big Picture
9
2.1 Embedded or Not?
10
2.1.1 BIOS Versus Bootloader
11
2.2 Anatomy of an Embedded System
12
2.2.1 Typical Embedded Linux Setup
13
2.2.2 Starting the Target Board
14
2.2.3 Booting the Kernel
16
2.2.4 Kernel Initialization: Overview
18
2.2.5 First User Space Process: init
19
2.3 Storage Considerations
20
2.3.1 Flash Memory
20
2.3.2 NAND Flash
22
2.3.3 Flash Usage
23
2.3.4 Flash File Systems
24
2.3.5 Memory Space
25
2.3.6 Execution Contexts
26
2.3.7 Process Virtual Memory
28
2.3.8 Cross-Development Environment
30
2.4 Embedded Linux Distributions
32
2.4.1 Commercial Linux Distributions
33
2.4.2 Do-It-Yourself Linux Distributions
33
2.5 Summary
34
2.5.1 Suggestions for Additional Reading
35
Chapter 3 Processor Basics
37
3.1 Stand-Alone Processors
38
3.1.1 IBM 970FX
39
3.1.2 Intel Pentium M
39
3.1.3 Intel Atoma
40
3.1.4 Freescale MPC7448
40
3.1.5 Companion Chipsets
41
3.2 Integrated Processors: Systems on Chip
43
3.2.1 Power Architecture
44
3.2.2 Freescale Power Architecture
44
3.2.3 Freescale PowerQUICC I
45
3.2.4 Freescale PowerQUICC II
46
3.2.5 PowerQUICC II Pro
47
3.2.6 Freescale PowerQUICC III
48
3.2.7 Freescale QorIQa
48
3.2.8 AMCC Power Architecture
50
3.2.9 MIPS
53
3.2.10 Broadcom MIPS
54
3.2.11 Other MIPS
55
3.2.12 ARM
55
3.2.13 TI ARM
56
3.2.14 Freescale ARM
58
3.2.15 Other ARM Processors
59
3.3 Other Architectures
59
3.4 Hardware Platforms
60
3.4.1 CompactPCI
60
3.4.2 ATCA
60
3.5 Summary
61
3.5.1 Suggestions for Additional Reading
62
Chapter 4 The Linux Kernel: A Different Perspective
63
4.1 Background
64
4.1.1 Kernel Versions
65
4.1.2 Kernel Source Repositories
67
4.1.3 Using git to Download a Kernel
68
4.2 Linux Kernel Construction
68
4.2.1 Top-Level Source Directory
69
4.2.2 Compiling the Kernel
69
4.2.3 The Kernel Proper: vmlinux
72
4.2.4 Kernel Image Components
73
4.2.5 Subdirectory Layout
77
4.3 Kernel Build System
78
4.3.1 The Dot-Config
78
4.3.2 Configuration Editor(s
80
4.3.3 Makefile Targets
83
4.4 Kernel Configuration
89
4.4.1 Custom Configuration Options
91
4.4.2 Kernel Makefiles
95
4.5 Kernel Documentation
96
4.6 Obtaining a Custom Linux Kernel
96
4.6.1 What Else Do I Need
97
4.7 Summary
97
4.7.1 Suggestions for Additional Reading
98
Chapter 5 Kernel Initialization
99
5.1 Composite Kernel Image: Piggy and Friends
100
5.1.1 The Image Object
103
5.1.2 Architecture Objects
104
5.1.3 Bootstrap Loader
105
5.1.4 Boot Messages
106
5.2 Initialization Flow of Control
109
5.2.1 Kernel Entry Point: head.o
111
5.2.2 Kernel Startup: main.c
113
5.2.3 Architecture Setup
114
5.3 Kernel Command-Line Processing
115
5.3.1 The __setup Macro
116
5.4 Subsystem Initialization
122
5.4.1 The *__initcall Macros
122
5.5 The init Thread
125
5.5.1 Initialization Via initcalls
126
5.5.2 initcall_debug
127
5.5.3 Final Boot Steps
127
5.6 Summary
129
5.6.1 Suggestions for Additional Reading
130
Chapter 6 User Space Initialization
131
6.1 Root File System
132
6.1.1 FHS: File System Hierarchy Standard
133
6.1.2 File System Layout
133
6.1.3 Minimal File System
134
6.1.4 The Embedded Root FS Challenge
136
6.1.5 Trial-and-Error Method
137
6.1.6 Automated File System Build Tools
137
6.2 Kernel's Last Boot Steps
137
6.2.1 First User Space Program
139
6.2.2 Resolving Dependencies
139
6.2.3 Customized Initial Process
140
6.3 The init Process
140
6.3.1 inittab
143
6.3.2 Sample Web Server Startup Script
145
6.4 Initial RAM Disk
146
6.4.1 Booting with initrd
147
6.4.2 Bootloader Support for initrd
148
6.4.3 initrd Magic: linuxrc
150
6.4.4 The initrd Plumbing
151
6.4.5 Building an initrd Image
152
6.5 Using initramfs
153
6.5.1 Customizing initramfs
154
6.6 Shutdown
156
6.7 Summary
156
6.7.1 Suggestions for Additional Reading
157
Chapter 7 Bootloaders
159
7.1 Role of a Bootloader
160
7.2 Bootloader Challenges
161
7.2.1 DRAM Controller
161
7.2.2 Flash Versus RAM
162
7.2.3 Image Complexity
162
7.2.4 Execution Context
165
7.3 A Universal Bootloader: Das U-Boot
166
7.3.1 Obtaining U-Boot
166
7.3.2 Configuring U-Boot
167
7.3.3 U-Boot Monitor Commands
169
7.3.4 Network Operations
170
7.3.5 Storage Subsystems
173
7.3.6 Booting from Disk
174
7.4 Porting U-Boot
174
7.4.1 EP405 U-Boot Port
175
7.4.2 U-Boot Makefile Configuration Target
176
7.4.3 EP405 First Build
177
7.4.4 EP405 Processor Initialization
178
7.4.5 Board-Specific Initialization
181
7.4.6 Porting Summary
184
7.4.7 U-Boot Image Format
185
7.5 Device Tree Blob (Flat Device Tree
187
7.5.1 Device Tree Source
189
7.5.2 Device Tree Compiler
192
7.5.3 Alternative Kernel Images Using DTB
193
7.6 Other Bootloaders
194
7.6.1 Lilo
194
7.6.2 GRUB
195
7.6.3 Still More Bootloaders
197
7.7 Summary
197
7.7.1 Suggestions for Additional Reading
198
Chapter 8 Device Driver Basics
201
8.1 Device Driver Concepts
202
8.1.1 Loadable Modules
203
8.1.2 Device Driver Architecture
204
8.1.3 Minimal Device Driver Example
204
8.1.4 Module Build Infrastructure
205
8.1.5 Installing a Device Driver
209
8.1.6 Loading a Module
210
8.1.7 Module Parameters
211
8.2 Module Utilities
212
8.2.1 insmod
212
8.2.2 lsmod
213
8.2.3 modprobe
213
8.2.4 depmod
214
8.2.5 rmmod
215
8.2.6 modinfo
216
8.3 Driver Methods
217
8.3.1 Driver File System Operations
217
8.3.2 Allocation of Device Numbers
220
8.3.3 Device Nodes and mknod
220
8.4 Bringing It All Together
222
8.5 Building Out-of-Tree Drivers
223
8.6 Device Drivers and the GPL
224
8.7 Summary
225
8.7.1 Suggestions for Additional Reading
226
Chapter 9 File Systems
227
9.1 Linux File System Concepts
228
9.1.1 Partitions
229
9.2 ext2
230
9.2.1 Mounting a File System
232
9.2.2 Checking File System Integrity
233
9.3 ext3
235
9.4 ext4
237
9.5 ReiserFS
238
9.6 JFFS2
239
9.6.1 Building a JFFS2 Image
240
9.7 cramfs
242
9.8 Network File System
244
9.8.1 Root File System on NFS
246
9.9 Pseudo File Systems
248
9.9.1 /proc File System
249
9.9.2 sysfs
252
9.10 Other File Systems
255
9.11 Building a Simple File System
256
9.12 Summary
258
9.12.1 Suggestions for Additional Reading
259
Chapter 10 MTD Subsystem
261
10.1 MTD Overview
262
10.1.1 Enabling MTD Services
263
10.1.2 MTD Basics
265
10.1.3 Configuring MTD on Your Target
267
10.2 MTD Partitions
267
10.2.1 Redboot Partition Table Partitioning
269
10.2.2 Kernel Command-Line Partitioning
273
10.2.3 Mapping Driver
274
10.2.4 Flash Chip Drivers
276
10.2.5 Board-Specific Initialization
276
10.3 MTD Utilities
279
10.3.1 JFFS2 Root File System
281
10.4 UBI File System
284
10.4.1 Configuring for UBIFS
284
10.4.2 Building a UBIFS Image
284
10.4.3 Using UBIFS as the Root File System
287
10.5 Summary
287
10.5.1 Suggestions for Additional Reading
288
Chapter 11 BusyBox
289
11.1 Introduction to BusyBox
290
11.1.1 BusyBox Is Easy
291
11.2 BusyBox Configuration
291
11.2.1 Cross-Compiling BusyBox
293
11.3 BusyBox Operation
293
11.3.1 BusyBox init
297
11.3.2 Sample rcS Initialization Script
299
11.3.3 BusyBox Target Installation
300
11.3.4 BusyBox Applets
302
11.4 Summary
303
11.4.1 Suggestions for Additional Reading
304
Chapter 12 Embedded Development Environment
305
12.1 Cross-Development Environment
306
12.1.1 "Hello World" Embedded
307
12.2 Host System Requirements
311
12.2.1 Hardware Debug Probe
311
12.3 Hosting Target Boards
312
12.3.1 TFTP Server
312
12.3.2 BOOTP/DHCP Server
313
12.3.3 NFS Server
316
12.3.4 Target NFS Root Mount
318
12.3.5 U-Boot NFS Root Mount Example
320
12.4 Summary
322
12.4.1 Suggestions for Additional Reading
323
Chapter 13 Development Tools
325
13.1 GNU Debugger (GDB)
326
13.1.1 Debugging a Core Dump
327
13.1.2 Invoking GDB
329
13.1.3 Debug Session in GDB
331
13.2 Data Display Debugger
333
13.3 cbrowser/cscope
335
13.4 Tracing and Profiling Tools
337
13.4.1 strace
337
13.4.2 strace Variations
341
13.4.3 ltrace
343
13.4.4 ps
344
13.4.5 top
346
13.4.6 mtrace
348
13.4.7 dmalloc
350
13.4.8 Kernel Oops
353
13.5 Binary Utilities
355
13.5.1 readelf
355
13.5.2 Examining Debug Information Using readelf
357
13.5.3 objdump
359
13.5.4 objcopy
360
13.6 Miscellaneous Binary Utilities
361
13.6.1 strip
361
13.6.2 addr2line
361
13.6.3 strings
362
13.6.4 ldd
362
13.6.5 nm
363
13.6.6 prelink
364
13.7 Summary
364
13.7.1 Suggestions for Additional Reading
365
Chapter 14 Kernel Debugging Techniques
367
14.1 Challenges to Kernel Debugging
368
14.2 Using KGDB for Kernel Debugging
369
14.2.1 KGDB Kernel Configuration
371
14.2.2 Target Boot with KGDB Support
372
14.2.3 Useful Kernel Breakpoints
376
14.2.4 Sharing a Console Serial Port with KGDB
377
14.2.5 Debugging Very Early Kernel Code
379
14.2.6 KGDB Support in the Mainline Kernel
380
14.3 Kernel Debugging Techniques
381
14.3.1 gdb Remote Serial Protocol
382
14.3.2 Debugging Optimized Kernel Code
385
14.3.3 GDB User-Defined Commands
392
14.3.4 Useful Kernel GDB Macros
393
14.3.5 Debugging Loadable Modules
402
14.3.6 printk Debugging
407
14.3.7 Magic SysReq Key
409
14.4 Hardware-Assisted Debugging
410
14.4.1 Programming Flash Using a JTAG Probe
411
14.4.2 Debugging with a JTAG Probe
413
14.5 When It Doesn't Boot
417
14.5.1 Early Serial Debug Output
417
14.5.2 Dumping the printk Log Buffer
417
14.5.3 KGDB on Panic
420
14.6 Summary
421
14.6.1 Suggestions for Additional Reading
422
Chapter 15 Debugging Embedded Linux Applications
423
15.1 Target Debugging
424
15.2 Remote (Cross) Debugging
424
15.2.1 gdbserver
427
15.3 Debugging with Shared Libraries
429
15.3.1 Shared Library Events in GDB
431
15.4 Debugging Multiple Tasks
435
15.4.1 Debugging Multiple Processes
435
15.4.2 Debugging Multithreaded Applications
438
15.4.3 Debugging Bootloader/Flash Code
441
15.5 Additional Remote Debug Options
442
15.5.1 Debugging Using a Serial Port
442
15.5.2 Attaching to a Running Process
442
15.6 Summary
443
15.6.1 Suggestions for Additional Reading
444
Chapter 16 Open Source Build Systems
445
16.1 Why Use a Build System?
446
16.2 Scratchbox
447
16.2.1 Installing Scratchbox
447
16.2.2 Creating a Cross-Compilation Target
448
16.3 Buildroot
451
16.3.1 Buildroot Installation
451
16.3.2 Buildroot Configuration
451
16.3.3 Buildroot Build
452
16.4 OpenEmbedded
454
16.4.1 OpenEmbedded Composition
455
16.4.2 BitBake Metadata
456
16.4.3 Recipe Basics
456
16.4.4 Metadata Tasks
460
16.4.5 Metadata Classes
461
16.4.6 Configuring OpenEmbedded
462
16.4.7 Building Images
463
16.5 Summary
464
16.5.1 Suggestions for Additional Reading
464
Chapter 17 Linux and Real Time
465
17.1 What Is Real Time
466
17.1.1 Soft Real Time
466
17.1.2 Hard Real Time
467
17.1.3 Linux Scheduling
467
17.1.4 Latency
467
17.2 Kernel Preemption
469
17.2.1 Impediments to Preemption
469
17.2.2 Preemption Models
471
17.2.3 SMP Kernel
472
17.2.4 Sources of Preemption Latency
473
17.3 Real-Time Kernel Patch
473
17.3.1 Real-Time Features
475
17.3.2 O(1) Scheduler
476
17.3.3 Creating a Real-Time Process
477
17.4 Real-Time Kernel Performance Analysis
478
17.4.1 Using Ftrace for Tracing
478
17.4.2 Preemption Off Latency Measurement
479
17.4.3 Wakeup Latency Measurement
481
17.4.4 Interrupt Off Timing
483
17.4.5 Soft Lockup Detection
484
17.5 Summary
485
17.5.1 Suggestion for Additional Reading
485
Chapter 18 Universal Serial Bus
487
18.1 USB Overview
488
18.1.1 USB Physical Topology
488
18.1.2 USB Logical Topology
490
18.1.3 USB Revisions
491
18.1.4 USB Connectors
492
18.1.5 USB Cable Assemblies
494
18.1.6 USB Modes
494
18.2 Configuring USB
495
18.2.1 USB Initialization
497
18.3 sysfs and USB Device Naming
500
18.4 Useful USB Tools
502
18.4.1 USB File System
502
18.4.2 Using usbview
504
18.4.3 USB Utils (lsusb
507
18.5 Common USB Subsystems
508
18.5.1 USB Mass Storage Class
508
18.5.2 USB HID Class
511
18.5.3 USB CDC Class Drivers
512
18.5.4 USB Network Support
515
18.6 USB Debug
516
18.6.1 usbmon
517
18.6.2 Useful USB Miscellanea
518
18.7 Summary
519
18.7.1 Suggestions for Additional Reading
519
Chapter 19 udev
521
19.1 What Is udev?
522
19.2 Device Discovery
523
19.3 Default udev Behavior
525
19.4 Understanding udev Rules
527
19.4.1 Modalias
530
19.4.2 Typical udev Rules Configuration
533
19.4.3 Initial System Setup for udev
535
19.5 Loading Platform Device Drivers
538
19.6 Customizing udev Behavior
540
19.6.1 udev Customization Example: USB Automounting
540
19.7 Persistent Device Naming
541
19.7.1 udev Helper Utilities
542
19.8 Using udev with busybox
545
19.8.1 busybox mdev
545
19.8.2 Configuring mdev
547
19.9 Summary
548
19.9.1 Suggestions for Additional Reading
548
Appendix A GNU Public License
549
Preamble
550
Terms and Conditions for Copying, Distribution, and Modification
551
No Warranty
555
Appendix B U-Boot Configurable Commands
557
Appendix C BusyBox Commands
561
Appendix D SDRAM Interface Considerations
571
D.1 SDRAM Basics
572
D.1.1 SDRAM Refresh
573
D.2 Clocking
574
D.3 SDRAM Setup
575
D.4 Summary
580
D.4.1 Suggestions for Additional Reading
580
Appendix E Open Source Resources
581
Source Repositories and Developer Information
582
Mailing Lists
582
Linux News and Developments
583
Open Source Legal Insight and Discussion
583
Appendix F Sample BDI-2000 Configuration File
585
Index
593