A simple Linux kernel module that implements a character device driver with a corresponding test program.

.
├── Makefile              # Build configuration
├── README.md             # This file
├── src/                  # Source files
│   └── mychardev.c       # Kernel module source code
├── test/                 # Test files
│   └── test_mychardev.c  # User-space test program
└── build/                # Build artifacts (generated)
    ├── mychardev.ko      # Compiled kernel module
    ├── test_mychardev    # Test executable
    └── ...               # Other build files

• Linux development environment
• Kernel headers for your running kernel
• GCC compiler
• Make utility

On Ubuntu/Debian:

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

On CentOS/RHEL/Fedora:

sudo yum groupinstall "Development Tools"
sudo yum install kernel-devel-$(uname -r)

make

This builds both the kernel module and the test program.

make module

make test

make clean

make install
# or manually:
sudo insmod build/mychardev.ko

make info
# or manually:
modinfo build/mychardev.ko

lsmod | grep mychardev

sudo ./build/test_mychardev

make remove
# or manually:
sudo rmmod mychardev

All build artifacts are placed in the build/ directory:

• mychardev.ko - The compiled kernel module
• test_mychardev - The test executable
• *.o, *.mod* - Intermediate object files
• Module.symvers, modules.order - Kernel build metadata

The source directories (src/ and test/) remain clean and contain only source code.

1. Edit source files in src/ or test/
2. Build with make
3. Test by loading the module and running the test program
4. Debug using kernel logs: dmesg | tail
5. Clean up with make clean when needed

• Ensure kernel headers are installed for your running kernel
• Check that you have sufficient permissions
• Verify GCC and make are installed

• Check dmesg for kernel messages
• Ensure the module isn't already loaded: lsmod | grep mychardev
• Verify you're running as root/sudo for module operations

• Module loading/unloading requires root privileges
• Use sudo for make install, make remove, and running test programs

# Build everything
make

# Load the module
make install

# Get hold of the major number that the module was registered with
sudo dmesg | tail -5

sudo mknod /dev/mychardev c <major_number> 0

# Check it's loaded
lsmod | grep mychardev

# Run the test
sudo ./build/test_mychardev

# Check kernel logs
dmesg | tail

# Unload the module
make remove

# Clean up build files
make clean

• The kernel module creates a character device that can be accessed from user space
• The test program demonstrates how to interact with the device
• All build artifacts are isolated in the build/ directory
• The project uses the Linux kernel build system (kbuild) for proper module compilation