get rid of lkmc package, move userland and kernel-modules to top

Rationale: we already had a non buildroot build system,
maintaining both will be hard, and having short paths is more awesome.

kernel_modules/ioctl.c

@@ -0,0 +1,72 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#ioctl */
+
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/printk.h> /* printk */
+#include <linux/uaccess.h> /* copy_from_user, copy_to_user */
+
+#include "../include/ioctl.h"
+
+static struct dentry *debugfs_file;
+
+static long unlocked_ioctl(struct file *filp, unsigned int cmd, unsigned long argp)
+{
+	void __user *arg_user;
+	union {
+		int i;
+		lkmc_ioctl_struct s;
+	} arg_kernel;
+
+	arg_user = (void __user *)argp;
+	pr_info("cmd = %x\n", cmd);
+	switch (cmd) {
+		case LKMC_IOCTL_INC:
+			if (copy_from_user(&arg_kernel.i, arg_user, sizeof(arg_kernel.i))) {
+				return -EFAULT;
+			}
+			pr_info("0 arg = %d\n", arg_kernel.i);
+			arg_kernel.i += 1;
+			if (copy_to_user(arg_user, &arg_kernel.i, sizeof(arg_kernel.i))) {
+				return -EFAULT;
+			}
+		break;
+		case LKMC_IOCTL_INC_DEC:
+			if (copy_from_user(&arg_kernel.s, arg_user, sizeof(arg_kernel.s))) {
+				return -EFAULT;
+			}
+			pr_info("1 arg = %d %d\n", arg_kernel.s.i, arg_kernel.s.j);
+			arg_kernel.s.i += 1;
+			arg_kernel.s.j -= 1;
+			if (copy_to_user(arg_user, &arg_kernel.s, sizeof(arg_kernel.s))) {
+				return -EFAULT;
+			}
+		break;
+		default:
+			return -EINVAL;
+		break;
+	}
+	return 0;
+}
+
+static const struct file_operations fops = {
+	.owner = THIS_MODULE,
+	.unlocked_ioctl = unlocked_ioctl
+};
+
+static int myinit(void)
+{
+	/* ioctl permissions are not automatically restricted by rwx as for read / write,
+	 * but we could of course implement that ourselves:
+	 * https://stackoverflow.com/questions/29891803/user-permission-check-on-ioctl-command */
+	debugfs_file = debugfs_create_file("lkmc_ioctl", 0, NULL, NULL, &fops);
+	return 0;
+}
+
+static void myexit(void)
+{
+	debugfs_remove(debugfs_file);
+}
+
+module_init(myinit)
+module_exit(myexit)
+MODULE_LICENSE("GPL");