add task 8
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50
README.md
50
README.md
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@ -180,6 +180,56 @@ echo "bonjour12" > /dev/eudyptula
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* [Linux Kernel Labs - Character device drivers](https://linux-kernel-labs.github.io/refs/heads/master/labs/device_drivers.html#read-and-write)
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* [Nihall - Misc character devices](https://nihaal.me/post/misc_char_devices/)
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## Tache 8
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L'ajout d'une nouvelle string dans le fichier ne supprime l'entièreté du
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contenu du fichier. J'ai testé les sémaphores avec des `msleep`
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(`<linux/delay.h>`) rajouté dans le code. Il est possible de tester en
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décommentant le premier `define`.
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```bash
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ls -l /sys/kernel/debug/eudyptula/
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# total 0
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# -rw-rw-r-- 1 root root 0 Jan 9 22:46 foo
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# -rw-rw-rw- 1 root root 0 Jan 9 22:44 id
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# -r--r--r-- 1 root root 0 Jan 9 22:45 jiffies
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echo pouet > /sys/kernel/debug/eudyptula/foo
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cat /sys/kernel/debug/eudyptula/foo
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# pouet
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echo coucou ! > /sys/kernel/debug/eudyptula/foo
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cat /sys/kernel/debug/eudyptula/foo
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# coucou !
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cat /sys/kernel/debug/eudyptula/id
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# pouetpouet
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echo congruent > /sys/kernel/debug/eudyptula/id
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echo $?
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# 0
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echo pouet > /sys/kernel/debug/eudyptula/id
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# bash: echo: write error: Invalid argument
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echo $?
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# 1
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echo pouet > /sys/kernel/debug/eudyptula/jiffies
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# bash: echo: write error: Permission denied
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cat /sys/kernel/debug/eudyptula/jiffies
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# 4345895105
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cat /sys/kernel/debug/eudyptula/jiffies
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# 4345895338
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echo pouet > /sys/kernel/debug/eudyptula/foo &
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cat /sys/kernel/debug/eudyptula/foo
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# cat: /sys/kernel/debug/eudyptula/foo: Invalid argument
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cat /sys/kernel/debug/eudyptula/foo &
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cat /sys/kernel/debug/eudyptula/foo &
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echo pouet > /sys/kernel/debug/eudyptula/foo
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# bash: echo: write error: Invalid argument
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rmmod hello
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ls -l /sys/kernel/debug/eudyptula/
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# ls: cannot access '/sys/kernel/debug/eudyptula/': No such file or directory
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```
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* [DebugFS (Documentation kernel)](https://docs.kernel.org/filesystems/debugfs.html)
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* [Chapitre 3, Linux Device Drivers, 3rd Edition](https://lwn.net/Kernel/LDD3/)
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* [Jiffies, Linux Kernel Development 2nd Edition](https://litux.nl/mirror/kerneldevelopment/0672327201/ch10lev1sec3.html)
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## Informations diverses
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Je liste dans cette section quelques informations que j'ai pu découvrir en
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9
task_08/Makefile
Normal file
9
task_08/Makefile
Normal file
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@ -0,0 +1,9 @@
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obj-m += debugfs.o
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PWD := $(CURDIR)
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all:
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make -C /lib/modules/$(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
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162
task_08/debugfs.c
Normal file
162
task_08/debugfs.c
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@ -0,0 +1,162 @@
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// SPDX-License-Identifier: GPL-2.0
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//#define DEBUG 1
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#include <asm/page.h>
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#include <linux/debugfs.h>
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#include <linux/delay.h>
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#include <linux/jiffies.h>
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#include <linux/module.h>
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#include <linux/rwsem.h>
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#ifdef DEBUG
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#include <linux/kernel.h>
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#endif
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#define BUFFER_LENGTH 10
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static struct dentry *folder;
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static struct dentry *id_file;
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static struct dentry *foo_file;
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static char *id_msg;
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static char *foo_msg;
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static struct rw_semaphore foo_sem;
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static ssize_t id_read(struct file *, char __user *buffer, size_t length, loff_t *offset)
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{
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int bytes = 0;
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const char *msg_tmp = id_msg;
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/*
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* TODO
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if (!*(msg_tmp + *offset)) {
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*offset = 0;
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return 0;
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}
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*/
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msg_tmp += *offset;
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while (*msg_tmp && bytes < length) {
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put_user(*(msg_tmp), (buffer + bytes));
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bytes++;
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msg_tmp++;
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}
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*offset += bytes;
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return bytes;
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}
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static ssize_t id_write(struct file *, const char __user *buffer,
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size_t size, loff_t *)
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{
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int ret;
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char *tmp_buffer;
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if (size == 0)
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return 0;
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tmp_buffer = kzalloc(BUFFER_LENGTH, GFP_KERNEL);
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if (copy_from_user(tmp_buffer, buffer, BUFFER_LENGTH)) {
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kfree(tmp_buffer);
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return -EINVAL;
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}
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*(tmp_buffer + BUFFER_LENGTH - 1) = '\0';
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pr_info("Test %s-\n", tmp_buffer);
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if (!strcmp(tmp_buffer, "congruent"))
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ret = BUFFER_LENGTH;
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else
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ret = -EINVAL;
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kfree(tmp_buffer);
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return ret;
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}
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static const struct file_operations id_fops = {
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.owner = THIS_MODULE,
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.read = id_read,
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.write = id_write,
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};
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static ssize_t foo_read(struct file *, char __user *buffer, size_t count, loff_t *offset)
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{
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int bytes = -EINVAL;
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int tmp_len = strlen(foo_msg);
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if (*offset > tmp_len) bytes = -EFAULT;
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else if (down_read_trylock(&foo_sem))
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{
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char *tmp_str = foo_msg + *offset;
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tmp_len = strlen(tmp_str);
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bytes = tmp_len > count ? count : tmp_len;
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if (copy_to_user(buffer, tmp_str, bytes)) bytes = -EFAULT;
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else *offset += bytes;
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#ifdef DEBUG
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msleep(5000);
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#endif
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up_read(&foo_sem);
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}
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return bytes;
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}
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static ssize_t foo_write(struct file *, const char __user *buffer,
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size_t count, loff_t * offset)
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{
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int bytes = -EINVAL;
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if ((*offset + count) > PAGE_SIZE) bytes = -EFAULT;
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else if (down_write_trylock(&foo_sem))
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{
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bytes = count;
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if (copy_from_user(foo_msg, buffer, bytes)) bytes = -EINVAL;
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#ifdef DEBUG
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msleep(5000);
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#endif
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up_write(&foo_sem);
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}
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return bytes;
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}
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static const struct file_operations foo_fops = {
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.owner = THIS_MODULE,
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.read = foo_read,
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.write = foo_write,
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};
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static int __init my_init(void)
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{
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init_rwsem(&foo_sem);
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id_msg = kmalloc(12, GFP_KERNEL);
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foo_msg = kmalloc(PAGE_SIZE, GFP_KERNEL);
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strcpy(id_msg, "pouetpouet\n");
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pr_info("Coucou le gens !!!!\n");
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folder = debugfs_create_dir("eudyptula", NULL);
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id_file = debugfs_create_file("id", 0666, folder, NULL, &id_fops);
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debugfs_create_u64("jiffies", 0444, folder, &jiffies_64);
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foo_file = debugfs_create_file("foo", 0664, folder, NULL, &foo_fops);
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return 0;
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}
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static void __exit my_exit(void)
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{
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debugfs_remove_recursive(folder);
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kfree(id_msg);
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kfree(foo_msg);
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pr_info("Tschuss !!!\n");
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}
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module_init(my_init);
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module_exit(my_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("rick <rick@gnous.eu>");
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MODULE_DESCRIPTION("Module pour tester le debugfs.");
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