A hello world Linux kernel module

.gitignore

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+*.cmd
+*.ko
+*.mod*
+*.o
+.helloworld.o.d
+.vagrant
+Module.symvers
+modules.order

Makefile

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+obj-m += helloworld.o
+
+all:
+	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
+
+clean:
+	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

README.md

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+## kernmod
+
+A hello world Linux kernel module and build environment in Debian GNU/Linux.
+
+
+### Public Domain Dedication
+Copyright (C) 2021  Kris Lamoureux
+
+Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

Vagrantfile

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+Vagrant.configure("2") do |config|
+  config.vm.box = "debian/bullseye64"
+  config.vm.synced_folder ".", "/vagrant"
+  config.vm.network "private_network", type: "dhcp"
+  config.vm.provision "shell", path: "build.sh"
+end

build.sh

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+#!/bin/bash
+
+export DEBIAN_FRONTEND=noninteractive
+apt-get update
+apt-get install build-essential linux-headers-$(uname -r) -y
+
+cd /vagrant
+make
+modinfo helloworld.ko
+insmod helloworld.ko
+cat /proc/modules | grep helloworld
+rmmod helloworld
+cat /var/log/messages | grep helloworld

helloworld.c

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+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+
+#define DRIVER_AUTHOR "Kris Lamoureux"
+#define DRIVER_DESC   "Hello world kernel module"
+
+int init_module(void)
+{
+	printk(KERN_INFO "helloworld: hello, world\n");
+	return 0;
+}
+
+void cleanup_module(void)
+{
+	printk(KERN_INFO "helloworld: goodbye, world\n");
+}
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);