add assignement 00 to 08

07/Makefile

@@ -0,0 +1,9 @@
+obj-m += fortytwo-debugfs.o 
+fortytwo-debugfs-y = main.o id.o foo.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

07/foo.c

@@ -0,0 +1,60 @@
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/debugfs.h>
+#include <linux/mm.h>
+#include <linux/mutex.h>
+
+extern struct dentry *module_dir;
+
+ssize_t foo_read(struct file *f, char __user *buf, size_t len, loff_t *off);
+ssize_t foo_write(struct file *f, const char __user *buf, size_t len, loff_t *off);
+int init_foo(void);
+
+char buffer[PAGE_SIZE];
+size_t buffer_len = 0;
+DEFINE_MUTEX(rw_lock);
+
+static const struct file_operations fops = {
+	.owner = THIS_MODULE,
+	.read = foo_read,
+	.write = foo_write,
+};
+
+
+ssize_t foo_read(struct file *f, char __user *buf, size_t len, loff_t *off)
+{
+	size_t read;
+	
+	mutex_lock(&rw_lock);
+	read = simple_read_from_buffer(buf, len, off, buffer, buffer_len);
+	mutex_unlock(&rw_lock);
+	return read;
+}
+
+
+ssize_t foo_write(struct file *f, const char __user *buf, size_t len, loff_t *off)
+{
+	if (len > sizeof(buffer))
+		return -EINVAL;
+	mutex_lock(&rw_lock);
+	if (copy_from_user(buffer, buf, len))
+	{
+		mutex_unlock(&rw_lock);
+		return -EINVAL;
+	}
+	buffer_len = len;
+	mutex_unlock(&rw_lock);
+	return len;
+}
+
+int init_foo(void)
+{
+	struct dentry *ret;
+
+	mutex_init(&rw_lock);
+	ret = debugfs_create_file("foo", 0644, module_dir, NULL, &fops);
+	if (IS_ERR(ret)) return PTR_ERR(ret);
+	return 0;
+}

07/id.c

@@ -0,0 +1,54 @@
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/debugfs.h>
+
+#define VALUE "tomoron"
+
+extern struct dentry *module_dir;
+ssize_t id_read(struct file *f, char __user *buf, size_t len, loff_t *off);
+ssize_t id_write(struct file *f, const char __user *buf, size_t len, loff_t *off);
+int init_id(void);
+
+
+static const struct file_operations fops = {
+	.owner = THIS_MODULE,
+	.read = id_read,
+	.write = id_write,
+};
+
+ssize_t id_read(struct file *f, char __user *buf, size_t len, loff_t *off)
+{
+	char msg[] = VALUE;
+	pr_info("someone read from the file\n");
+	return simple_read_from_buffer(buf, len, off, msg, sizeof(msg) - 1);
+}
+
+
+ssize_t id_write(struct file *f, const char __user *buf, size_t len, loff_t *off)
+{
+	char kbuf[64];
+	if (len > sizeof(kbuf) - 1)
+		return -EINVAL;
+	if (copy_from_user(kbuf, buf, len))
+		return -EINVAL;
+
+	kbuf[len] = '\0';
+
+	if (strcmp(kbuf, VALUE) == 0){
+		pr_info("someone wrote the right string\n");
+		return len;
+	}
+	pr_info("someone wrote the wrong string\n");
+	return -EINVAL;
+}
+
+int init_id(void)
+{
+	struct dentry *ret;
+	ret = debugfs_create_file("id", 0666, module_dir, NULL, &fops);
+	if(IS_ERR(ret))
+		return PTR_ERR(ret);
+	return 0;
+}

07/main.c

@@ -0,0 +1,44 @@
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/jiffies.h>
+#include <linux/debugfs.h>
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("hello world module");
+
+#define FILENAME "id"
+
+int init_id(void);
+int init_foo(void);
+
+struct dentry *module_dir;
+
+static int __init fortytwo_debug_init(void) 
+{ 
+	int err = 0;
+
+	pr_info("creating fortytwo debug dir\n");
+	module_dir = debugfs_create_dir("fortytwo", NULL);
+	if (IS_ERR(module_dir))
+		return PTR_ERR(module_dir);
+
+	debugfs_create_u64("jiffies", 0444, module_dir, (uint64_t *)(&jiffies));
+
+	err = init_id();
+	if (err) return err;
+	err = init_foo();
+	if(err) return err;
+	return 0;
+} 
+
+static void __exit fortytwo_debug_exit(void) 
+{ 
+	pr_info("removing forytwo debug dir\n"); 
+	debugfs_remove(module_dir);
+} 
+
+module_init(fortytwo_debug_init); 
+module_exit(fortytwo_debug_exit);
+

07/output.log

@@ -0,0 +1,22 @@
+-bash-5.0$ ls -la
+total 0
+drwxr-xr-x  2 root root 0 Jul 10 01:52 .
+drwxrwxrwx 27 root root 0 Jul 10 01:52 ..
+-rw-r--r--  1 root root 0 Jul 10 01:52 foo
+-rw-rw-rw-  1 root root 0 Jul 10 01:52 id
+-r--r--r--  1 root root 0 Jul 10 01:52 jiffies
+-bash-5.0$ echo hello-world > foo
+-bash: foo: Permission denied
+-bash-5.0$ echo hello-world | sudo tee foo
+hello-world
+-bash-5.0$ cat foo
+hello-world
+-bash-5.0$ cat id
+tomoron-bash-5.0$ echo -n patate > id
+-bash: echo: write error: Invalid argument
+-bash-5.0$ echo -n tomoron > id
+-bash-5.0$ cat jiffies
+4295652460
+-bash-5.0$ cat jiffies
+4295653284
+-bash-5.0$