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Realtime Offset Kernel Module

Description

This Linux kernel module provides the offset between clock_monotonic and clock_realtime via a device interface. It is a simple and efficient way to retrieve the time offset between these two clocks directly from the kernel space, ensuring high precision and low latency.

Installation

Prerequisites

  • Linux kernel headers installed. You can usually install them via your distribution's package manager. For example, on Ubuntu: 
    sudo apt install linux-headers-$(uname -r)

Building the Module

  1. Clone the repository:

    git clone https://github.com/HedgeHawk/realtime-offset.git
cd realtime-offset

  2. Build the module:

    make

  3. Insert the module into the kernel:

    sudo insmod realtime_offset.ko

  4. Check that the module has been loaded:

    lsmod | grep realtime_offset

Usage

The module creates a device file at /dev/realtime_offset. You can read from this file to get the current offset between clock_monotonic and clock_realtime.

Example:

cat /dev/realtime_offset

Code Overview

Key Functions

  • offset_init: Initializes the kernel module, registers the device class and creates the device.
  • offset_exit: Cleans up when the module is removed, destroying the device and unregistering the device class.
  • dev_open: Called when the device is opened.
  • dev_release: Called when the device is released.
  • dev_read: Reads the offset between clock_monotonic and clock_realtime and returns it to the user space.

Device File Operations

The file_operations structure is defined with the following callbacks:

  • open: Points to dev_open.
  • read: Points to dev_read.
  • release: Points to dev_release.

License

This project is licensed under the GPL License - see the LICENSE file for details.

Acknowledgements

Thanks to the Linux kernel community and all contributors who have helped in building and improving the kernel, making projects like this possible.