Embedded Linux System Programming

Introduction to Toolchain

• What is a Toolchain?
• Definition and role in software development
• High-level overview of how toolchains streamline the development process
• Importance of Toolchains
• Benefits of using a standardized toolchain
• Impact on development efficiency and software performance

Components of a Toolchain

• Overview of Toolchain Components
• Breakdown of the major components included in a typical toolchain
• How these components interact with each other
• Essential Tools Overview
• Introduction to the core tools that make up a toolchain: compilers, assemblers, linkers, libraries, and debugging tools

Compilers and Assemblers

• Understanding Compilers
• Role of compilers in transforming source code into machine code
• Examples of popular compilers: GCC, Clang
• Working with Assemblers
• Explanation of assemblers and their function in the toolchain
• Discussion on the transition from high-level code to assembly

Linkers and Libraries

• Role of Linkers
• Definition and purpose of linkers in software compilation
• Static vs. dynamic linking: pros and cons
• Using Libraries
• Types of libraries (static and shared libraries)
• Best practices for managing libraries in development projects

Source Debugging Tools

• Overview of Debugging Tools
• Role of debugging tools in maintaining software quality
• Introduction to tools like GDB.

Introduction to Libraries & Linkages

• Overview of Library Linkages
• Definition of libraries and their role in software development
• Importance of linkages in building and maintaining software

Types of Library Linkages

• Understanding Different Linkages
• High-level differentiation between static and dynamic linkages
• Scenarios for using different types of linkages

Static Libraries and Linkages

• Introduction to Static Libraries
• Definition and characteristics of static libraries
• Creating and using static libraries (e.g., using ar, ranlib)
• Linking with Static Libraries
• Step-by-step process on how to link static libraries in a project
• Compilation and linking examples

Shared Libraries and Linkages

• Introduction to Shared Libraries
• Benefits and drawbacks of using shared libraries
• Creating and managing shared libraries (e.g., using gcc -shared)
• Linking with Shared Libraries
• How to dynamically link shared libraries at compile time
• Setting environment variables like LD_LIBRARY_PATH

Dynamic Linking and Loaders

• Dynamic Linking Mechanics
• How dynamic linking works at runtime
• Role of the dynamic linker/loader (e.g., ld-linux.so)
• Tools for Managing Dynamic Linkages
• Using tools like ldd to inspect dynamic dependencies
• Understanding the use of ldconfig

Managing Dynamic Linkages

• Advanced Management Techniques
• Handling versioning in shared libraries
• Strategies for avoiding dependency conflicts
• Runtime Dynamic Linking
• Techniques for loading libraries at runtime using dlopen, dlsym, and dlclose

Best Practices and Common Issues

• Best Practices in Library Management
• Guidelines for effectively managing static and dynamic libraries
• Tips for maintaining binary compatibility and managing ABI (Application Binary Interface)
• Common Issues and Troubleshooting
• Diagnosing and resolving typical problems with library linkages

Introduction to Cross-toolchain

• What is a Cross-toolchain?
• Basic definition and purpose of cross-toolchains
• Explanation of cross-compilation and its relevance in software development

Components of a Cross-toolchain

• Overview of Key Components
• Brief overview of compilers, linkers, and libraries used in cross-toolchains
• Importance of each component in the cross-compilation process

Sourcing a Cross-toolchain

• Finding Cross-toolchains
• Basic sources for obtaining cross-toolchains for popular architectures like ARM, RiscV, and PPC
• Tips on choosing a suitable cross-toolchain based on project needs

Setting up a Cross-toolchain Environment

• Environment Setup Basics
• Simple steps to configure a development environment for using a cross-toolchain
• Setting essential environment variables and understanding their roles

Generating a Simple Cross-toolchain Using Buildroot

• Introduction to Buildroot
• What is Buildroot? High-level overview of its role in generating cross-toolchains
• Simple steps to initiate Buildroot configuration for a basic toolchain

Building and Running a Simple Program

• Cross-compiling a Simple Application
• Demonstrating how to compile a basic “Hello World” program for a target architecture

Introduction to Operating Systems

• Overview
• Definition and main functions of an operating system.
  • Generic Kernel Architecture

Types of Operating Systems

• Usage Categories
• General-Purpose, Real-Time, and Embedded systems.

Software Architectures

• Design modles
• Monolithic, Microkernel, and Modular models explained.
  • Pro & Cons for each of the types

Introduction to the Linux Kernel

• Linux Kernel Overview
• Basic history and characteristics of the Linux kernel.

Linux Distributions

• Overview
• Role and examples of popular Linux distributions

• Kernel Source Layout
• Pre-requisites
• Kernel Configuration
• Kernel Compilation
• Installing the Kernel
• Kernel Bootup
• Cross-compiling the Kernel

• Need for virtual address spaces
• Kernel & User address spaces
• Application binary interface (ABI)
• User address space layout
• System calls

• Introduction to program loading
• Program to Process transition
• Process footprint
• Process descriptor (PCB)
• Process States

• Understanding System Calls
• System call transitions
• Introduction to APIs
• *nix API standards
• APIs and application portability

• Process address space layout
• Stack Segment: Usage & Management
• Heap Segment: Usage & Management
• Mmap Segment usage
• Dynamic memory allocations using malloc() package
• Demand Paging & Lazy Allocations
• Memory Locking
• Troubleshooting & Debugging

• Components of I/O subsystem
• Objectives of Linux I/O model
• Virtual file system
• File system services
• I/O cache
• Understanding file descriptors & inode structures

• Introduction to common file APIs
• Accessing file attributes
• Standard I/O operations
• File control operations

Introduction to I/O Multiplexing

• Overview of I/O Multiplexing
  • Definition and significance of I/O multiplexing
  • Comparison with traditional blocking and non-blocking I/O
• Common Use Cases
  • Scenarios where I/O multiplexing is essential
  • Benefits of using I/O multiplexing in network applications and servers

Basics of I/O Multiplexing

• Understanding File Descriptors
  • Role of file descriptors in I/O operations
  • Managing file descriptors in Linux
• Blocking vs. Non-Blocking I/O
  • Configuring file descriptors for non-blocking mode
  • Handling I/O without blocking the main application flow

Core Multiplexing Techniques

• Select System Call
  • Mechanics of the select function
  • Limitations and performance considerations
• Poll System Call
  • Introduction to poll
  • Differences and advantages over select

Advanced Multiplexing with epoll

• • Introduction to epoll
    • Benefits of using epoll over select and poll
    • Understanding the epoll API
  • Implementing epoll
    • Practical examples of setting up and using epoll
    • Handling edge and level trigger modes

• Process scheduler architecture
• Policy Groups and priorities
• Fair-share policies
• Real-time Policies
• Deadline policies
• CPU affinity configuration

• What are signals ?
• Signal types & categories
• Signal generation and delivery
• Signal management data-structures
• Switching signal dispositions
  •  Setting up async signal handlers
• Using signals for process communication
• Blocking & Unblocking signal delivery
• Timer signals
• Use cases and best practices

• Introduction to concurrent applications
• Understanding need for concurrent apps
• Standard Concurrency models

• Unix threads API (fork(), vfork(), execve())
  • Enumerating child process
  • Child process memory footprint
  • Monitoring child process
  • Handling child process termination events
  • Copy-on-write optimization
  • fork() vs vfork()
  • execve() family of calls

• Linux threads API
  • Light-weight process defined (LWP)
  • LWP vs Process
  • clone() API
    • Basic capabilities
    • Differences and Similarities to fork()
    • CLONE_* flags
    • clone() threads
    • Memory sharing and Management
    • Namespace isolation

Introduction to Pthreads

• Overview of Multithreading Concepts
  • Difference between processes and threads
  • Benefits and challenges of multithreading
• Introduction to the Pthreads Library
  • History and standards
  • Basic functions and data structures
  • Platform specific extensions to standard library

Creating and Managing Threads

• Creating Threads
  • Using pthread_create
  • Handling thread attributes
• Thread Termination
  • Exiting threads cleanly using pthread_exit
  • Handling return values from threads
• Joining and Detaching Threads
  • Synchronizing thread termination with pthread_join
  • Detaching threads for independent operation
• Thread Attributes
  • Scheduling Policies & Priorities
  • Thread CPU affinity
  • Thread stack management

Thread Synchronization

• Producer/Consumer models
• Readers-Writers problem solutions
• Semaphores
  • Understanding and using semaphores for synchronization
  • Differences between standard semaphores and Pthreads semaphores
• Condition Variables
  • Using condition variables to synchronize thread activities
  • pthread_cond_wait, pthread_cond_signal, and pthread_cond_broadcast
• Barrier Synchronization
  • Barriers for synchronization
  • Practical usage 

Data Synchronization Basics

• Need for  Data-Synchronization
  • Understanding race conditions
  • Use cases for synchronization
• Wait Locking Implementations
  • Creating and destroying a lock
  • Locking and unlocking 
  • Strategies to avoid deadlocks
• Poll-locking Implementations
  • Poll locking usage  
  • Implementing poll-locking with Pthreads
•  Read/Write Locks
• • Understanding read/write locks for improved concurrency
  • Practical examples and when to use them over mutexes

Scalability and Architectural Considerations

• Scaling Multithreaded Applications
  • Challenges in scaling on multi-core and multiprocessor systems
  • Techniques for maximizing performance and minimizing contention

Thread Cancellation and Cleanup

• Concepts of Thread Cancellation
• Understanding thread cancellation and its necessity
• Types of cancellation: asynchronous vs. deferred cancellation
• cancellation points 

Implementing Thread Cancellation

• Initiating Cancellation
  • How to send a cancellation request using pthread_cancel
• Cancellation Options
  • Setting thread cancellation options with pthread_setcancelstate and pthread_setcanceltype
  • Differences and implications of each cancellation type

Managing Resources During Cancellation

• Cleanup Handlers
  • Registering cleanup handlers using pthread_cleanup_push and pthread_cleanup_pop
  • Examples of using cleanup handlers 
  • Thread-Safe Resource Management
  • Strategies to ensure resources are properly managed during cancellation

Introduction to Socket Programming

• Overview of Socket APIs
  • History and standards
  • Basic concepts and functionality
• Types of Sockets
  • Stream vs. Datagram
  • TCP/IP sockets vs. UNIX domain sockets
• Development Environment Setup
  • Required tools and libraries

Basics of TCP/IP Sockets

• Understanding TCP/IP
  • Protocol layers
  • TCP vs. UDP characteristics
• Creating and Managing Connections
  • Establishing connections
  • Client-server architecture principles
• Data Transmission
  • Handling data sending and receiving
  • Connection management

Advanced TCP/IP Socket Programming

• Error Handling and Debugging
  • Common issues and troubleshooting
  • Packet analysis tools
• Socket Options and Configuration
  • Manipulating options for performance tuning
  • Implementing timeouts and adjusting buffers
• Multiplexing and Non-blocking I/O
  • Techniques for managing multiple connections
  • Implementing asynchronous data handling

Basics of UNIX Domain Sockets

• Introduction to UNIX Domain Sockets
  • Benefits and comparison with TCP/IP
  • Communication patterns
• Setup and Configuration
  • Establishing UNIX domain connections
  • Namespace and path considerations
• Data Transfer Techniques
  • Modes of data transfer
  • Ensuring data integrity

Overview of IPC

• Definition and importance of IPC

• Different IPC mechanisms available in Linux

• Introduction to librt

• Role and features of the librt library

• Setting up the environment for IPC development

Basic IPC Mechanisms

• Pipes and FIFOs

• Basics of pipes and named pipes (FIFOs)

• Practical examples and use cases

• Message Queues

• Introduction to POSIX message queues

• Creating, sending, and receiving messages

Shared Memory

• Basics of Shared Memory

• Concept of shared memory in IPC

• Creating and mapping shared memory regions

• Synchronization in Shared Memory

• Using mutexes and condition variables in shared memory

• Ensuring safe access to shared memory

Semaphores

• Using POSIX Semaphores

• Understanding semaphores for process synchronization

• Creating and managing semaphores

• Advanced Semaphore Techniques

• Handling complex synchronization scenarios

• Practical examples and patterns

Advanced Messaging Techniques

• Real-time Messaging with mqueue

• Enhancing IPC with real-time features of message queues

• Setting attributes and real-time messaging priorities

• Robustness and Fault Tolerance

• Error handling and recovery in IPC scenarios

Memory-mapped Files

• Introduction to Memory-mapped Files

• Using mmap for efficient file access

• Scenarios for using memory-mapped files in IPC

• Performance Considerations

• Advantages and trade-offs of using memory-mapped files

Synchronization Techniques

• Advanced Synchronization

• Barrier synchronization

• Read-write locks for complex IPC scenarios

• Practical Synchronization Problems

• Solving common synchronization challenges in IPC