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LazencaLazenca
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Linux Kernel exploitation Tutorial.
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‎01.Development of Kernel Module/01.Hello world!/Makefile

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

‎01.Development of Kernel Module/01.Hello world!/sample.c

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#include <linux/module.h> /* Needed by all modules */
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#include <linux/kernel.h> /* Needed for KERN_INFO */
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int init_module(void) {
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printk(KERN_INFO "Hello world - Lazenca0x0.\n");
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return 0;
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}
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void cleanup_module(void) {
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printk(KERN_INFO "Goodbye world - Lazenca0x0\n.");
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}

‎01.Development of Kernel Module/02.Character Device Drivers/Example [struct file_operations - .open]/Makefile

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obj-m := chardev.o
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all:
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make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) modules
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clean:
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make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) clean
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‎01.Development of Kernel Module/02.Character Device Drivers/Example [struct file_operations - .open]/chardev.c

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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/cdev.h>
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#include <linux/sched.h>
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#include <linux/device.h>
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#include <linux/slab.h>
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#include <asm/current.h>
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#include <linux/uaccess.h>
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#define DEVICE_NAME "chardev"
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#define DEVICE_FILE_NAME "chardev"
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#define MAJOR_NUM 100
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static int chardev_open(struct inode *inode, struct file *file)
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{
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printk("chardev_open");
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return 0;
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}
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struct file_operations chardev_fops = {
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.open = chardev_open,
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};
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static int chardev_init(void)
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{
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int ret_val;
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ret_val = register_chrdev(MAJOR_NUM, DEVICE_NAME, &chardev_fops);
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if (ret_val < 0) {
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printk(KERN_ALERT "%s failed with %d\n",
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"Sorry, registering the character device ", ret_val);
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return ret_val;
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}
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printk(KERN_INFO "%s The major device number is %d.\n",
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"Registeration is a success", MAJOR_NUM);
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printk(KERN_INFO "If you want to talk to the device driver,\n");
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printk(KERN_INFO "you'll have to create a device file. \n");
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printk(KERN_INFO "We suggest you use:\n");
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printk(KERN_INFO "mknod %s c %d 0\n", DEVICE_FILE_NAME, MAJOR_NUM);
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printk(KERN_INFO "The device file name is important, because\n");
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printk(KERN_INFO "the ioctl program assumes that's the\n");
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printk(KERN_INFO "file you'll use.\n");
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return 0;
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}
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static void chardev_exit(void)
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{
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unregister_chrdev(MAJOR_NUM, DEVICE_NAME);
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}
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module_init(chardev_init);
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module_exit(chardev_exit);

‎01.Development of Kernel Module/02.Character Device Drivers/Example [struct file_operations .open, .release, .read, .write]/Makefile

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obj-m := chardev.o
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all:
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make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) modules
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clean:
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make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) clean
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‎01.Development of Kernel Module/02.Character Device Drivers/Example [struct file_operations .open, .release, .read, .write]/chardev.c

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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/cdev.h>
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#include <linux/sched.h>
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#include <linux/device.h>
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#include <linux/slab.h>
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#include <asm/current.h>
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#include <linux/uaccess.h>
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MODULE_LICENSE("Dual BSD/GPL");
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#define DRIVER_NAME "chardev"
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#define BUFFER_SIZE 256
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static const unsigned int MINOR_BASE = 0;
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static const unsigned int MINOR_NUM = 2;
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static unsigned int chardev_major;
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static struct cdev chardev_cdev;
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static struct class *chardev_class = NULL;
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static int chardev_open(struct inode *, struct file *);
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static int chardev_release(struct inode *, struct file *);
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static ssize_t chardev_read(struct file *, char *, size_t, loff_t *);
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static ssize_t chardev_write(struct file *, const char *, size_t, loff_t *);
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struct file_operations chardev_fops = {
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.open = chardev_open,
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.release = chardev_release,
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.read = chardev_read,
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.write = chardev_write,
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};
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struct data {
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unsigned char buffer[BUFFER_SIZE];
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};
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static int chardev_init(void)
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{
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int alloc_ret = 0;
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int cdev_err = 0;
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int minor;
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dev_t dev;
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printk("The chardev_init() function has been called.");
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alloc_ret = alloc_chrdev_region(&dev, MINOR_BASE, MINOR_NUM, DRIVER_NAME);
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if (alloc_ret != 0) {
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printk(KERN_ERR "alloc_chrdev_region = %d\n", alloc_ret);
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return -1;
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}
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//Get the major number value in dev.
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chardev_major = MAJOR(dev);
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dev = MKDEV(chardev_major, MINOR_BASE);
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//initialize a cdev structure
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cdev_init(&chardev_cdev, &chardev_fops);
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chardev_cdev.owner = THIS_MODULE;
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//add a char device to the system
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cdev_err = cdev_add(&chardev_cdev, dev, MINOR_NUM);
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if (cdev_err != 0) {
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printk(KERN_ERR "cdev_add = %d\n", alloc_ret);
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unregister_chrdev_region(dev, MINOR_NUM);
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return -1;
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}
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chardev_class = class_create(THIS_MODULE, "chardev");
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if (IS_ERR(chardev_class)) {
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printk(KERN_ERR "class_create\n");
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cdev_del(&chardev_cdev);
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unregister_chrdev_region(dev, MINOR_NUM);
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return -1;
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}
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for (minor = MINOR_BASE; minor < MINOR_BASE + MINOR_NUM; minor++) {
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device_create(chardev_class, NULL, MKDEV(chardev_major, minor), NULL, "chardev%d", minor);
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}
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return 0;
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}
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static void chardev_exit(void)
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{
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int minor;
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dev_t dev = MKDEV(chardev_major, MINOR_BASE);
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printk("The chardev_exit() function has been called.");
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for (minor = MINOR_BASE; minor < MINOR_BASE + MINOR_NUM; minor++) {
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device_destroy(chardev_class, MKDEV(chardev_major, minor));
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}
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class_destroy(chardev_class);
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cdev_del(&chardev_cdev);
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unregister_chrdev_region(dev, MINOR_NUM);
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}
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static int chardev_open(struct inode *inode, struct file *file)
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{
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char *str = "helloworld";
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int ret;
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struct data *p = kmalloc(sizeof(struct data), GFP_KERNEL);
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printk("The chardev_open() function has been called.");
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if (p == NULL) {
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printk(KERN_ERR "kmalloc - Null");
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return -ENOMEM;
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}
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ret = strlcpy(p->buffer, str, sizeof(p->buffer));
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if(ret > strlen(str)){
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printk(KERN_ERR "strlcpy - too long (%d)",ret);
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}
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file->private_data = p;
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return 0;
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}
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static int chardev_release(struct inode *inode, struct file *file)
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{
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printk("The chardev_release() function has been called.");
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if (file->private_data) {
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kfree(file->private_data);
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file->private_data = NULL;
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}
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return 0;
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}
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static ssize_t chardev_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos)
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{
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struct data *p = filp->private_data;
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printk("The chardev_write() function has been called.");
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printk("Before calling the copy_to_user() function : %p, %s",p->buffer,p->buffer);
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if (copy_from_user(p->buffer, buf, count) != 0) {
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return -EFAULT;
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}
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printk("After calling the copy_to_user() function : %p, %s",p->buffer,p->buffer);
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return count;
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}
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static ssize_t chardev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
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{
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struct data *p = filp->private_data;
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printk("The chardev_read() function has been called.");
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if(count > BUFFER_SIZE){
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count = BUFFER_SIZE;
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}
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if (copy_to_user(buf, p->buffer, count) != 0) {
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return -EFAULT;
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}
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return count;
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}
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module_init(chardev_init);
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module_exit(chardev_exit);

‎01.Development of Kernel Module/02.Character Device Drivers/Example [struct file_operations .open, .release, .read, .write]/test

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‎01.Development of Kernel Module/02.Character Device Drivers/Example [struct file_operations .open, .release, .read, .write]/test.c

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#include <stdio.h>
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#include <stdlib.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <errno.h>
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int main()
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{
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static char buff[256];
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int fd0_A, fd0_B, fd1_A;
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if ((fd0_A = open("/dev/chardev0", O_RDWR)) < 0) perror("open");
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if ((fd0_B = open("/dev/chardev0", O_RDWR)) < 0) perror("open");
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if ((fd1_A = open("/dev/chardev1", O_RDWR)) < 0) perror("open");
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if (write(fd0_A, "0_A", 4) < 0) perror("write");
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if (write(fd0_B, "0_B", 4) < 0) perror("write");
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if (write(fd1_A, "1_A", 4) < 0) perror("write");
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if (read(fd0_A, buff, 4) < 0) perror("read");
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printf("%s\n", buff);
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if (read(fd0_B, buff, 4) < 0) perror("read");
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printf("%s\n", buff);
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if (read(fd1_A, buff, 4) < 0) perror("read");
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printf("%s\n", buff);
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if (close(fd0_A) != 0) perror("close");
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if (close(fd0_B) != 0) perror("close");
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if (close(fd1_A) != 0) perror("close");
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return 0;
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}

‎01.Development of Kernel Module/02.Character Device Drivers/Example [struct file_operations .open, .release, .read, .write]/test1

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‎01.Development of Kernel Module/03.ioctl(Input,Output control)/Makefile

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obj-m := chardev.o
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MY_CFLAGS += -g -DDEBUG
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ccflags-y += ${MY_CFLAGS}
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CC += ${MY_CFLAGS}
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all:
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make -C /lib/modules/4.18.0/build M=$(shell pwd) modules
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debug:
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make -C /lib/modules/4.18.0/build M=$(PWD) modules EXTRA_CFLAGS="$(MY_CFLAGS)"
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clean:
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make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) clean
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