Chapter 1, Linux System Architecture, covers the key basics: the Unix design philosophy and the Linux system architecture. Along the way, other important aspects—CPU privilege levels, the processor ABI, and what system calls really are—are dealt with.
Chapter 2, Virtual Memory, dives into clearing up common misconceptions about what virtual memory really is and why it is key to modern OS design; the layout of the process virtual address space is covered too.
Chapter 3, Resource Limits, delves into the topic of per-process resource limits and the APIs governing their usage.
Chapter 4, Dynamic Memory Allocation, initially covers the basics of the popular malloc family of APIs, then dives into more advanced aspects, such as the program break, how malloc really behaves, demand paging, memory locking and protection, and using the alloca function.
Chapter 5, Linux Memory Issues, introduces you to the (unfortunately) prevalent memory defects that end up in our projects due to a lack of understanding of the correct design and use of memory APIs. Defects such as undefined behavior (in general), overflow and underflow bugs, leakage, and others are covered.
Chapter 6, Debugging Tools for Memory Issues, shows how to leverage existing tools, including the compiler itself, Valgrind, and AddressSanitizer, which is used to detect the memory issues you will have seen in the previous chapter.
Chapter 7, Process Credentials, is the first of two chapters focused on having you think about and understand security and privilege from a system perspective. Here, you'll learn about the traditional security model – a set of process credentials – as well as the APIs for manipulating them. Importantly, the concepts of setuid-root processes and their security repercussions are delved into.
Chapter 8, Process Capabilities, introduces you to the modern POSIX capabilities model and how security can benefit when application developers learn to use and leverage this model instead of the traditional model (seen in the previous chapter). What capabilities are, how to embed them, and practical design for security is also looked into.
Chapter 9, Process Execution, is the first of four chapters dealing with the broad area of process management (execution, creation, and signaling). In this particular chapter, you'll learn how the (rather unusual) Unix exec axiom behaves and how to use the API set (the exec family) to exploit it.
Chapter 10, Process Creation, delves into how exactly the fork(2) system call behaves and should be used; we depict this via our seven rules of fork. The Unix fork-exec-wait semantic is described (diving into the wait APIs as well), orphan and zombie processes are also covered.
Chapter 11, Signaling – Part I, deals with the important topic of signals on the Linux platform: the what, the why, and the how. We cover the powerful sigaction(2) system call here, along with topics such as reentrant and signal-async safety, sigaction flags, signal stacks, and others.
Chapter 12, Signaling – Part II, continues our coverage of signaling, what with it being a large topic. We take you through the correct way to write a signal handler for the well-known and fatal segfault, working with real-time signals, delivering signal to processes, performing IPC with signals, and alternate means to handle signals.
Chapter 13, Timers, teaches you about the important (and signal-related) topic of how to set up and handle timers in real-world Linux applications. We first cover the traditional timer APIs and quickly move onto the modern POSIX interval timers and how to use them to this end. Two interesting, small projects are presented and walked through.
Chapter 14, Multithreading with Pthreads Part I – Essentials, is the first of a trilogy on multithreading with the pthreads framework on Linux. Here, we introduce you to what exactly a thread is, how it differs from a process, and the motivation (in terms of design and performance) for using threads. The chapter then guides you through the essentials of writing a pthreads application on Linux ,covering thread creation, termination, joining, and more.
Chapter 15, Multithreading with Pthreads Part II – Synchronization, is a chapter dedicated to the really important topic of synchronization and race prevention. You will first understand the issue at hand, then delve into the key topics of atomicity, locking, deadlock prevention, and others. Next, the chapter teaches you how to use pthreads synchronization APIs with respect to the mutex lock and condition variables.
Chapter 16, Multithreading with Pthreads Part III, completes our work on multithreading; we shed light on the key topics of thread safety, thread cancellation and cleanup, and handling signals in a multithreaded app. We round off the chapter with a discussion on the pros and cons of multithreading and address some FAQs.
Chapter 17, CPU Scheduling on Linux, introduces you to scheduling-related topics that the system programmer should be aware of. We cover the Linux process/thread state machine, the notion of real time and the three (minimal) POSIX CPU scheduling policies that the Linux OS brings to the table. Exploiting the available APIs, you'll learn how to write a soft real-time app on Linux. We finish the chapter with a brief look at the (interesting!) fact that Linux can be patched to work as an RTOS.
Chapter 18, Advanced File I/O, is completely focused on the more advanced ways of performing IO on Linux in order to gain maximum performance (as IO is often the bottleneck). You are briefly shown how the Linux IO stack is architected (the page cache being critical), and the APIs that give advice to the OS on file access patterns. Writing IO code for performance, as you'll learn, involves the use of technologies such as SG-I/O, memory mapping, DIO, and AIO.
Chapter 19, Troubleshooting and Best Practices, is a critical summation of the key points to do with troubleshooting on Linux. You'll be briefed upon the use of powerful tools, such as perf and tracing tools. Then, very importantly, the chapter attempts to summarize key points on software engineering in general and programming on Linux in particular, looking at industry best practices. We feel these are critical takeaways for any programmer.
Appendix A, File I/O Essentials, introduces you to performing efficient file I/O on the Linux platform, via both the streaming (stdio library layer) API set as well as the underlying system calls. Along the way, important information on buffering and its effects on performance are covered.
For this chapter refer to: https://www.packtpub.com/sites/default/files/downloads/File_IO_Essentials.pdf.
Appendix B, Daemon Processes, introduces you, in a succinct fashion, to the world of the daemon process on Linux. You'll be shown how to write a traditional SysV-style daemon process. There is also a brief note on what is involved in constructing a modern, new-style daemon process.
For this chapter refer to: https://www.packtpub.com/sites/default/files/downloads/Daemon_Processes.pdf.
