How do I write my own Linux kernel module with simple example?

The kernel modules will have a . ko extension. On a normal linux system, the kernel modules will reside inside /lib/modules//kernel/ directory….II. Write a Simple Hello World Kernel Module

  1. Installing the linux headers.
  2. Hello World Module Source Code.
  3. Create Makefile to Compile Kernel Module.

What is kernel module in Linux?

Kernel modules are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system. Custom codes can be added to Linux kernels via two methods.

How do kernel modules communicate?

If you want to communicate between two kernel modules you should use symbols (global variables or functions) which are exported by the other kernel module. netlink Sockets are used to communicate between kernel and userland.

How do I start developing a kernel?

First steps

  1. Download. Grab a copy of the mainline repository: git clone http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git.
  2. Configure. Make sure you have the gcc and binutils packages installed, as this is required to build the kernel.
  3. Build.
  4. Running in a VM.
  5. Books.

How do you code a kernel?

Building Linux Kernel

  1. Step 1: Download the Source Code.
  2. Step 2: Extract the Source Code.
  3. Step 3: Install Required Packages.
  4. Step 4: Configure Kernel.
  5. Step 5: Build the Kernel.
  6. Step 6: Update the Bootloader (Optional)
  7. Step 7: Reboot and Verify Kernel Version.

How do I build and install a kernel module?

The procedure to build (compile) and install the latest Linux kernel from source is as follows:

  1. Grab the latest kernel from kernel.org.
  2. Verify kernel.
  3. Untar the kernel tarball.
  4. Copy existing Linux kernel config file.
  5. Compile and build Linux kernel 5.16.
  6. Install Linux kernel and modules (drivers)
  7. Update Grub configuration.

What is a kernel module?

A kernel module (or loadable kernel mode) is an object file that contains code that can extend the kernel functionality at runtime (it is loaded as needed); When a kernel module is no longer needed, it can be unloaded. Most of the device drivers are used in the form of kernel modules.

How do I run a kernel module?

Loading a Module

  1. To load a kernel module, run modprobe module_name as root .
  2. By default, modprobe attempts to load the module from /lib/modules/kernel_version/kernel/drivers/ .
  3. Some modules have dependencies, which are other kernel modules that must be loaded before the module in question can be loaded.

Is a driver a kernel module?

Kernel modules do not define a main program. Kernel modules, including device drivers, have no main() routine. Instead, a kernel module is a collection of subroutines and data. A device driver is a kernel module that forms a software interface to an input/output (I/O) device.

How is a kernel written?

The kernel is written using GNU C and the GNU toolchain. While it adheres to the ISO C89 standard, it uses a number of extensions that are not featured in the standard. The kernel is a freestanding C environment, with no reliance on the standard C library, so some portions of the C standard are not supported.