🐧 Linux System Call Project

This project focuses on compiling and deploying a custom Linux kernel with an added system call that prints detailed information about a process to the kernel log buffer. The work demonstrates an understanding of Linux kernel internals, system call implementation, and kernel debugging using user-level C programs.

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📘 Overview

The goal of this project was to extend the Linux kernel by implementing a custom system call that provides insights into the internal state of any given process.
This system call accepts a process ID (PID) and prints key details — such as its name, state, PID, priority values, and parent process information — to the kernel log buffer.

By developing and testing this system call, the project provides hands-on experience in:

• Modifying kernel source code
• Rebuilding and deploying a custom Linux kernel
• Interacting with the kernel through user-space programs

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⚙️ Implementation Steps

1. Download and Set Up Linux Kernel

• Downloaded the official Linux kernel source code (version used: 5.11.14).
• Configured the kernel environment for building and testing.

2. Add Custom System Call

• Implemented a new system call in the kernel source tree.
• Modified the following files:
  • System call table
  • System call header file
  • Makefile in the relevant kernel directory
• The system call source file was added to handle the logic for retrieving and printing process details.

3. System Call Functionality

• The custom system call:
  • Accepts a process ID (PID) as input.
  • Retrieves the task_struct of the corresponding process.
  • Prints details including:
    • Process ID (PID)
    • Process Name
    • Process State
    • Static and Dynamic Priority
    • Parent Process ID and Name
  • Logs the output to the kernel log buffer, viewable using:

    dmesg

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🧪 Testing

Test Programs

• Developed multiple C programs to validate the functionality of the system call.
• Used fork() to create parent-child processes and observed their states.

Expected Behavior

• The parent process was observed in a waiting state.
• The child process was in a running state.
• All process details were correctly printed to the kernel log buffer.