Linux Kernel Process Tree Module

A Linux kernel module that creates multiple processes/threads in a binary tree structure and displays their task names, states, and process IDs in hierarchical format. Demonstrates kernel-level thread management, process tree visualization and memory management for Operating Systems project.

🎯 Project Overview

This project was developed as part of an Operating Systems course to demonstrate understanding of Linux kernel programming concepts. The kernel module creates a binary tree of kernel threads, where each node represents a process/thread with its associated metadata.

Problem Statement: Create a Linux kernel module that spawns multiple processes/threads (children and siblings) and outputs their task names, states, and process IDs in a tree structure while the task is executing.

✨ Features

• 🌳 Binary Tree Creation: Generates a hierarchical structure of kernel threads
• 📊 Process Information Display: Shows task names, PIDs, and parent-child relationships
• 🔄 Recursive Thread Management: Implements recursive thread creation and cleanup
• 🧠 Memory Management: Proper kernel memory allocation and deallocation
• 📝 Kernel Logging: Comprehensive logging using printk() for debugging
• 🔒 Signal Handling: Graceful thread termination with signal management
• 🏗️ Data Structures: Custom tree implementation using Linux kernel linked lists

🛠️ Tech Stack

Programming Languages

• C: Core kernel module implementation
• Makefile: Build configuration and compilation

Kernel APIs & Libraries

• linux/init.h - Module initialization/cleanup
• linux/module.h - Module metadata and macros
• linux/kernel.h - Kernel utility functions
• linux/sched.h - Process/task management
• linux/kthread.h - Kernel threading API
• linux/signal.h - Signal handling
• linux/slab.h - Memory allocation (kmalloc, kfree)
• linux/list.h - Kernel linked list implementation

Development Tools

• GCC: GNU Compiler Collection for kernel compilation
• Make: Build automation tool
• Linux Kernel Build System: For module compilation
• dmesg: Kernel message logging and debugging

System Requirements

• Linux Kernel: Version 4.x or higher
• Architecture: x86_64 (tested on Ubuntu/Debian)
• Permissions: Root/sudo access required

📋 Prerequisites

System Requirements

• Linux distribution (Ubuntu 20.04+ recommended)
• Kernel headers installed
• GCC compiler
• Make utility
• Root/sudo privileges

Installing Dependencies

Ubuntu/Debian:

sudo apt update
sudo apt install build-essential linux-headers-$(uname -r)

CentOS/RHEL/Fedora:

sudo yum groupinstall "Development Tools"
sudo yum install kernel-devel kernel-headers

Arch Linux:

sudo pacman -S base-devel linux-headers

🚀 Installation & Usage

1. Clone the Repository

git clone https://github.com/yourusername/linux-kernel-process-tree-module.git
cd linux-kernel-process-tree-module

2. Build the Module

make

Expected Output:

make -C /lib/modules/6.5.0-25-generic/build M=/home/user/project modules
make[1]: Entering directory '/usr/src/linux-headers-6.5.0-25-generic'
CC [M] /home/user/project/my_kernel_module12.o
MODPOST /home/user/project/Module.symvers
CC [M] /home/user/project/my_kernel_module12.mod.o
LD [M] /home/user/project/my_kernel_module12.ko
make[1]: Leaving directory '/usr/src/linux-headers-6.5.0-25-generic'

3. Load the Module

sudo insmod my_kernel_module.ko

4. View the Output

sudo dmesg 

5. Remove the Module

sudo rmmod my_kernel_module

6. Clean Build Files

make clean

📁 Project Structure

linux-kernel-process-tree-module/
├── my_kernel_module.c    # Main kernel module source code
├── Makefile               # Build configuration
├── README.md             # Project documentation
└── .gitignore           # Git ignore file (optional)

File Descriptions

• my_kernel_module.c: Core implementation containing thread creation, tree management, and cleanup logic
• Makefile: Defines build rules for kernel module compilation
• README.md: Comprehensive project documentation

🔧 How It Works

Architecture Overview

1. Module Initialization: Creates a root kernel thread
2. Binary Tree Construction: Recursively spawns child threads (2 per level)
3. Tree Traversal: Displays the complete hierarchy
4. Memory Management: Proper allocation/deallocation of tree nodes
5. Module Cleanup: Graceful termination of all threads

Key Components

1. Tree Node Structure

struct tree_node {
    int pid;                    // Process ID
    char name[16];             // Thread name
    struct list_head children; // List of child nodes
    struct list_head sibling;  // Sibling node link
};

2. Thread Function

• Each thread runs child_function()
• Handles signals for graceful termination
• Maintains interruptible sleep state

3. Tree Creation Algorithm

• Levels: Configurable depth (default: 3 levels)
• Branching: Binary tree (2 children per node)
• Naming: Pattern thread_<level>_<index>

4. Memory Management

• Uses kmalloc() for node allocation
• Implements proper cleanup with kfree()
• Handles allocation failures gracefully

📊 Sample Output

[INFO] Binary Tree Logger Module: Initialization
[INFO] Created root thread: PID=1234
[INFO] Created thread: PID=1235, Parent PID=1234, Level=1
[INFO] Created thread: PID=1236, Parent PID=1234, Level=1
[INFO] Created thread: PID=1237, Parent PID=1235, Level=2
[INFO] Created thread: PID=1238, Parent PID=1235, Level=2
[INFO] Created thread: PID=1239, Parent PID=1236, Level=2
[INFO] Created thread: PID=1240, Parent PID=1236, Level=2
[INFO] Process Tree Structure:
├── root_thread(1234)
    ├── thread_1_0(1235)
        ├── thread_2_0(1237)
        └── thread_2_1(1238)
    └── thread_1_1(1236)
        ├── thread_2_0(1239)
        └── thread_2_1(1240)

🐛 Troubleshooting

Common Issues

1. Compilation Errors

Problem: fatal error: linux/module.h: No such file or directory Solution:

sudo apt install linux-headers-$(uname -r)

2. Permission Denied

Problem: Operation not permitted when loading module Solution: Ensure you're using sudo:

sudo insmod my_kernel_module.ko

3. Module Already Loaded

Problem: File exists error Solution: Remove existing module first:

sudo rmmod my_kernel_module
sudo insmod my_kernel_module.ko

4. Build Directory Not Found

Problem: Missing kernel build directory Solution: Install matching kernel headers:

sudo apt install linux-headers-$(uname -r)

Debugging Tips

1. Check kernel logs: sudo dmesg
2. Verify module loading: lsmod | grep my_kernel_module
3. Check system resources: free -h and ps aux
4. Monitor system: Use htop or top while module runs

📚 Learning Outcomes

This project demonstrates proficiency in:

• Kernel Programming: Understanding of Linux kernel APIs and development practices
• Process Management: Creation and management of kernel threads
• Data Structures: Implementation of tree structures using kernel linked lists
• Memory Management: Proper allocation and deallocation in kernel space
• System Programming: Low-level programming concepts and debugging
• Concurrency: Thread synchronization and signal handling
• Build Systems: Makefile creation and kernel build process

🤝 Contributing

Contributions are welcome! Please follow these steps:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

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