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  • Book Overview & Buying Mastering Embedded Linux Programming
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Mastering Embedded Linux Programming

Mastering Embedded Linux Programming

By : Chris Simmonds
4.8 (20)
Buy this Book
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Mastering Embedded Linux Programming

Mastering Embedded Linux Programming

4.8 (20)
By: Chris Simmonds
Buy this Book

Overview of this book

Mastering Embedded Linux Programming takes you through the product cycle and gives you an in-depth description of the components and options that are available at each stage. You will begin by learning about toolchains, bootloaders, the Linux kernel, and how to configure a root filesystem to create a basic working device. You will then learn how to use the two most commonly used build systems, Buildroot and Yocto, to speed up and simplify the development process. Building on this solid base, the next section considers how to make best use of raw NAND/NOR flash memory and managed flash eMMC chips, including mechanisms for increasing the lifetime of the devices and to perform reliable in-field updates. Next, you need to consider what techniques are best suited to writing applications for your device. We will then see how functions are split between processes and the usage of POSIX threads, which have a big impact on the responsiveness and performance of the final device The closing sections look at the techniques available to developers for profiling and tracing applications and kernel code using perf and ftrace.
Table of Contents (16 chapters)
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Preface
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Free Chapter
1
1. Starting Out
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1. Starting Out
Selecting the right operating system
The players
Project lifecycle
Open source
Hardware for embedded Linux
Hardware used in this book
Software used in this book
Summary
2
2. Learning About Toolchains
2. Learning About Toolchains
What is a toolchain?
Types of toolchain - native versus cross toolchain
Choosing the C library
Finding a toolchain
Anatomy of a toolchain
Other tools in the toolchain
Looking at the components of the C library
Linking with libraries: static and dynamic linking
The art of cross compiling
Problems with cross compiling
Summary
3
3. All About Bootloaders
3. All About Bootloaders
What does a bootloader do?
The boot sequence
Booting with UEFI firmware
Moving from bootloader to kernel
Introducing device trees
Choosing a bootloader
U-Boot
Barebox
Summary
4
4. Porting and Configuring the Kernel
4. Porting and Configuring the Kernel
What does the kernel do?
Choosing a kernel
Building the kernel
Compiling
Cleaning kernel sources
Booting your kernel
Porting Linux to a new board
Additional reading
Summary
5
5. Building a Root Filesystem
5. Building a Root Filesystem
What should be in the root filesystem?
Programs for the root filesystem
Libraries for the root filesystem
Device nodes
The proc and sysfs filesystems
Kernel modules
Transfering the root filesystem to the target
Creating a boot ramdisk
The init program
Configuring user accounts
Starting a daemon process
A better way of managing device nodes
Configuring the network
Creating filesystem images with device tables
Mounting the root filesystem using NFS
Using TFTP to load the kernel
Additional reading
Summary
6
6. Selecting a Build System
6. Selecting a Build System
No more rolling your own embedded Linux
Build systems
Package formats and package managers
Buildroot
The Yocto Project
Further reading
Summary
7
7. Creating a Storage Strategy
7. Creating a Storage Strategy
Storage options
Accessing flash memory from the bootloader
Accessing flash memory from Linux
Filesystems for flash memory
Filesystems for NOR and NAND flash memory
Filesystems for managed flash
Read-only compressed filesystems
Temporary filesystems
Making the root filesystem read-only
Filesystem choices
Updating in the field
Further reading
Summary
8
8. Introducing Device Drivers
8. Introducing Device Drivers
The role of device drivers
Character devices
Block devices
Network devices
Finding out about drivers at runtime
Finding the right device driver
Device drivers in user-space
Writing a kernel device driver
Loading kernel modules
Discovering hardware configuration
Additional reading
Summary
9
9. Starting up - the init Program
9. Starting up - the init Program
After the kernel has booted
Introducing the init programs
BusyBox init
System V init
systemd
Further reading
Summary
10
10. Learning About Processes and Threads
10. Learning About Processes and Threads
Process or thread?
Processes
Threads
Scheduling
Further reading
Summary
11
11. Managing Memory
11. Managing Memory
Virtual memory basics
Kernel space memory layout
User space memory layout
Process memory map
Swap
Mapping memory with mmap
How much memory does my application use?
Per-process memory usage
Identifying memory leaks
Running out of memory
Further reading
Summary
12
12. Debugging with GDB
12. Debugging with GDB
The GNU debugger
Preparing to debug
Debugging applications using GDB
Remote debugging using gdbserver
Starting to debug
Debugging shared libraries
Just-in-time debugging
Debugging forks and threads
Core files
GDB user interfaces
Debugging kernel code
Additional reading
Summary
13
13. Profiling and Tracing
13. Profiling and Tracing
The observer effect
Beginning to profile
Profiling with top
Introducing perf
Other profilers: OProfile and gprof
Tracing events
Introducing Ftrace
Using LTTng
Using Valgrind for application profiling
Callgrind
Helgrind
Using strace to show system calls
Summary
14
14. Real-time Programming
14. Real-time Programming
What is real-time?
Identifying the sources of non-determinism
Understanding scheduling latency
Kernel preemption
The real-time Linux kernel (PREEMPT_RT)
Threaded interrupt handlers
Preemptible kernel locks
Getting the PREEMPT_RT patches
High resolution timers
Avoiding page faults in a real-time application
Interrupt shielding
Measuring scheduling latencies
Further reading
Summary
15
Index
Index

Project lifecycle

This book is divided into four sections that reflect the phases of a project. The phases are not necessarily sequential. Usually they overlap and you will need to jump back to revisit things that were done previously. However, they are representative of a developer's preoccupations as the project progresses:

  • Elements of embedded Linux (chapters 1 to 6) will help you set up the development environment and create a working platform for the later phases. It is often referred to as the "board bring-up" phase.
  • System architecture and design choices (chapters 7 to 9) will help you to look at some of the design decisions you will have to make concerning the storage of programs and data, how to divide work between kernel device drivers and applications, and how to initialize the system.
  • Writing embedded applications (chapters 10 and 11) show how to make effective use of the Linux process and threads model and how to manage memory in a resource-constrained device.
  • Debugging and optimizing performance (chapters 12 and 13) describe how to trace, profile, and debug your code in both the applications and the kernel.

The fifth section on real-time (Chapter 14, Real-time Programming) stands somewhat alone because it is a small, but important, category of embedded systems. Designing for real-time behavior has an impact on each of the four main phases.

The four elements of embedded Linux

Every project begins by obtaining, customizing, and deploying these four elements: the toolchain, the bootloader, the kernel, and the root filesystem. This is the topic of the first section of this book:

  • Toolchain: This consists of the compiler and other tools needed to create code for your target device. Everything else depends on the toolchain.
  • Bootloader: This is necessary to initialize the board and to load and boot the Linux kernel.
  • Kernel: This is the heart of the system, managing system resources and interfacing with hardware.
  • Root filesystem: This contains the libraries and programs that are run once the kernel has completed its initialization.

Of course, there is also a fifth element, not mentioned here. That is the collection of programs that are specific to your embedded application which make the device do whatever it is supposed to do, be it weigh groceries, display movies, control a robot, or fly a drone.

Typically you will be offered some or all of these elements as a package when you buy your SoC or board. But, for the reasons mentioned in the preceding paragraph, they may not be the best choices for you. I will give you the background to make the right selections in the first six chapters and I will introduce you to two tools that automate the whole process for you: Buildroot and the Yocto Project.

End of Section 4
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