corrections on 03 and 08, 09 done

03/main.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/delay.h>
@@ -7,21 +8,21 @@ MODULE_LICENSE("GPL");
 MODULE_AUTHOR("42");
 MODULE_DESCRIPTION("A module that does work");
 
-
-static int do_work(int *nbLoop)
+static int do_work(int *nb_loop)
 {
 	int x;
-	for (x = 0; x < *nbLoop; ++x) {
-		udelay(10);
-	}
-	if (*nbLoop > 10)
-		pr_info("do_work(): slept a long time\n");
-	return(x * *nbLoop);
+
+	for (x = 0; x < *nb_loop; ++x)
+		usleep_range(10);
+	if (*nb_loop > 10)
+		pr_info("%s: slept a long time\n", __func__);
+	return(x * *nb_loop);
 }
 
 static int __init module_example_42_init(void)
 {
 	int x = 10;
+
 	x = do_work(&x);
 	return x;
 }

08/main.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
@@ -9,12 +10,12 @@ MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Louis Solofrizzo <louis@ne02ptzero.me>");
 MODULE_DESCRIPTION("Useless module");
 
-static ssize_t myfd_read (struct file *fp, char __user *user,
-size_t size, loff_t *offs);
+static ssize_t myfd_read(struct file *fp, char __user *user,
+			 size_t size, loff_t *offs);
 static ssize_t myfd_write(struct file *fp, const char __user *user,
-size_t size, loff_t *offs);
+			  size_t size, loff_t *offs);
 
-static struct file_operations myfd_fops = {
+static const struct file_operations myfd_fops = {
 	.owner = THIS_MODULE,
 	.read = &myfd_read,
 	.write = &myfd_write
@@ -27,7 +28,8 @@ static struct miscdevice myfd_device = {
 };
 
 char str[PAGE_SIZE];
-DEFINE_MUTEX(rw_lock);
+
+DEFINE_MUTEX(rw_lock); //lock read/write operations of the /dev/reverse file
 
 static int __init myfd_init(void)
 {
@@ -45,25 +47,25 @@ ssize_t myfd_read(struct file *fp, char __user *user, size_t size, loff_t *offs)
 	ssize_t retval;
 	size_t len;
 	char *tmp;
-	
+
 	mutex_lock(&rw_lock);
 	len = strlen(str);
 	tmp = kmalloc(sizeof(char) * PAGE_SIZE, GFP_KERNEL);
-	for (size_t i = 0,j = len - 1; i < len; i++, j--) {
+	for (size_t i = 0, j = len - 1; i < len; i++, j--)
 		tmp[i] = str[j];
-	}
 	tmp[len] = 0;
 	retval = simple_read_from_buffer(user, size, offs, tmp, len);
 	mutex_unlock(&rw_lock);
+	kfree(tmp);
 	return retval;
 }
 
 ssize_t myfd_write(struct file *fp, const char __user *user, size_t size,
-		loff_t *offs)
+		   loff_t *offs)
 {
 	ssize_t res;
 
-	if(size >= (PAGE_SIZE - 1))
+	if (size >= (PAGE_SIZE - 1))
 		return -EINVAL;
 	mutex_lock(&rw_lock);
 	res = simple_write_to_buffer(str, size, offs, user, size);

09/Makefile

@@ -0,0 +1,9 @@
+obj-m += mounts.o 
+mounts-y = main.o rw.o
+PWD := $(CURDIR) 
+
+all: 
+	$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules 
+
+clean: 
+	$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

09/main.c

@@ -0,0 +1,44 @@
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+
+#include <linux/sched.h>
+#include <linux/nsproxy.h>
+#include <linux/mount.h>
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("create /proc/mymounts file that lists mounts");
+
+struct proc_dir_entry *proc_file;
+
+int list_mounts(struct seq_file *m, void *v);
+
+static int list_mounts_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, list_mounts, NULL);
+}
+
+static const struct proc_ops proc_fops = {
+	.proc_open = list_mounts_open,
+	.proc_read = seq_read,
+	.proc_lseek = seq_lseek,
+	.proc_release = single_release,
+};
+
+static int __init mounts_init(void) 
+{ 
+	proc_file = proc_create("mymounts", 0444, 0, &proc_fops);
+	if(IS_ERR(proc_file)) return PTR_ERR(proc_file);
+	return 0;
+} 
+
+static void __exit mounts_exit(void) 
+{ 
+	proc_remove(proc_file);
+} 
+
+module_init(mounts_init); 
+module_exit(mounts_exit);
+

09/rw.c

@@ -0,0 +1,41 @@
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+
+#include <linux/nsproxy.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <../fs/mount.h>
+
+int list_mounts(struct seq_file *m, void *v);
+
+int list_mounts(struct seq_file *m, void *v)
+{
+	struct rb_node *cur;
+	struct mount *mnt;
+	char *buf;
+	char *path;
+
+	cur = current->nsproxy->mnt_ns->mnt_first_node;
+
+	buf = kmalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
+	while(cur)
+	{
+		mnt = rb_entry(cur, struct mount, mnt_node);
+
+		struct path p = {
+    		.mnt = &mnt->mnt,
+    		.dentry = mnt->mnt.mnt_root,
+		};
+
+		path = d_path(&p, buf, PATH_MAX);
+		if(IS_ERR(path))
+			path = 0;
+		seq_printf(m, "%-10s	%s\n", mnt->mnt_devname, path);
+		cur = rb_next(cur);
+	}
+	kfree(buf);
+	return 0;
+}