A tiny loadable kernel module used for testing and learning. The module implements a simple guest book: by writing on the device, a message can be left, and by reading from the device the latest inserted message can be read.
To read the kernel log:
tail -f /var/log/kern.log
The test.sh script does a quick test compiling and loading the module, and also unloading it and deleting the generated files when it's done.
If you want to do the testing manually:
- To load the kernel module, compile it with
make, then a.kofile is produced. Run:
sudo insmod guestbook.ko
- To unload it:
sudo rmmod guestbook
-
Once the module is running, you can compile (just run
gcc -o tester tester.c) and runtester.cto see how it does. -
If you want to quickly remove the files generated with
make, runmake clean.
The module now creates (and deletes) its own device file via C code, and we have a tester.c program to test the module, so the section below is not needed anymore. I will keep it there in case anyone finds it useful.
Once it's running we want to create a node for the device in /dev:
cd /dev
# dev name c is for char device
sudo mknod guestbook c <major_number> 0
To see it in action do for example:
cat /dev/guestbook