add task 8

This commit is contained in:
rick 2024-01-10 00:06:10 +01:00
parent e2836073c6
commit 1441afda58
Signed by: Rick
GPG key ID: 5CBE8779CD27BCBA
3 changed files with 221 additions and 0 deletions

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@ -180,6 +180,56 @@ echo "bonjour12" > /dev/eudyptula
* [Linux Kernel Labs - Character device drivers](https://linux-kernel-labs.github.io/refs/heads/master/labs/device_drivers.html#read-and-write) * [Linux Kernel Labs - Character device drivers](https://linux-kernel-labs.github.io/refs/heads/master/labs/device_drivers.html#read-and-write)
* [Nihall - Misc character devices](https://nihaal.me/post/misc_char_devices/) * [Nihall - Misc character devices](https://nihaal.me/post/misc_char_devices/)
## Tache 8
L'ajout d'une nouvelle string dans le fichier ne supprime l'entièreté du
contenu du fichier. J'ai testé les sémaphores avec des `msleep`
(`<linux/delay.h>`) rajouté dans le code. Il est possible de tester en
décommentant le premier `define`.
```bash
ls -l /sys/kernel/debug/eudyptula/
# total 0
# -rw-rw-r-- 1 root root 0 Jan 9 22:46 foo
# -rw-rw-rw- 1 root root 0 Jan 9 22:44 id
# -r--r--r-- 1 root root 0 Jan 9 22:45 jiffies
echo pouet > /sys/kernel/debug/eudyptula/foo
cat /sys/kernel/debug/eudyptula/foo
# pouet
echo coucou ! > /sys/kernel/debug/eudyptula/foo
cat /sys/kernel/debug/eudyptula/foo
# coucou !
cat /sys/kernel/debug/eudyptula/id
# pouetpouet
echo congruent > /sys/kernel/debug/eudyptula/id
echo $?
# 0
echo pouet > /sys/kernel/debug/eudyptula/id
# bash: echo: write error: Invalid argument
echo $?
# 1
echo pouet > /sys/kernel/debug/eudyptula/jiffies
# bash: echo: write error: Permission denied
cat /sys/kernel/debug/eudyptula/jiffies
# 4345895105
cat /sys/kernel/debug/eudyptula/jiffies
# 4345895338
echo pouet > /sys/kernel/debug/eudyptula/foo &
cat /sys/kernel/debug/eudyptula/foo
# cat: /sys/kernel/debug/eudyptula/foo: Invalid argument
cat /sys/kernel/debug/eudyptula/foo &
cat /sys/kernel/debug/eudyptula/foo &
echo pouet > /sys/kernel/debug/eudyptula/foo
# bash: echo: write error: Invalid argument
rmmod hello
ls -l /sys/kernel/debug/eudyptula/
# ls: cannot access '/sys/kernel/debug/eudyptula/': No such file or directory
```
* [DebugFS (Documentation kernel)](https://docs.kernel.org/filesystems/debugfs.html)
* [Chapitre 3, Linux Device Drivers, 3rd Edition](https://lwn.net/Kernel/LDD3/)
* [Jiffies, Linux Kernel Development 2nd Edition](https://litux.nl/mirror/kerneldevelopment/0672327201/ch10lev1sec3.html)
## Informations diverses ## Informations diverses
Je liste dans cette section quelques informations que j'ai pu découvrir en Je liste dans cette section quelques informations que j'ai pu découvrir en

9
task_08/Makefile Normal file
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@ -0,0 +1,9 @@
obj-m += debugfs.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

162
task_08/debugfs.c Normal file
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@ -0,0 +1,162 @@
// SPDX-License-Identifier: GPL-2.0
//#define DEBUG 1
#include <asm/page.h>
#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/rwsem.h>
#ifdef DEBUG
#include <linux/kernel.h>
#endif
#define BUFFER_LENGTH 10
static struct dentry *folder;
static struct dentry *id_file;
static struct dentry *foo_file;
static char *id_msg;
static char *foo_msg;
static struct rw_semaphore foo_sem;
static ssize_t id_read(struct file *, char __user *buffer, size_t length, loff_t *offset)
{
int bytes = 0;
const char *msg_tmp = id_msg;
/*
* TODO
if (!*(msg_tmp + *offset)) {
*offset = 0;
return 0;
}
*/
msg_tmp += *offset;
while (*msg_tmp && bytes < length) {
put_user(*(msg_tmp), (buffer + bytes));
bytes++;
msg_tmp++;
}
*offset += bytes;
return bytes;
}
static ssize_t id_write(struct file *, const char __user *buffer,
size_t size, loff_t *)
{
int ret;
char *tmp_buffer;
if (size == 0)
return 0;
tmp_buffer = kzalloc(BUFFER_LENGTH, GFP_KERNEL);
if (copy_from_user(tmp_buffer, buffer, BUFFER_LENGTH)) {
kfree(tmp_buffer);
return -EINVAL;
}
*(tmp_buffer + BUFFER_LENGTH - 1) = '\0';
pr_info("Test %s-\n", tmp_buffer);
if (!strcmp(tmp_buffer, "congruent"))
ret = BUFFER_LENGTH;
else
ret = -EINVAL;
kfree(tmp_buffer);
return ret;
}
static const struct file_operations id_fops = {
.owner = THIS_MODULE,
.read = id_read,
.write = id_write,
};
static ssize_t foo_read(struct file *, char __user *buffer, size_t count, loff_t *offset)
{
int bytes = -EINVAL;
int tmp_len = strlen(foo_msg);
if (*offset > tmp_len) bytes = -EFAULT;
else if (down_read_trylock(&foo_sem))
{
char *tmp_str = foo_msg + *offset;
tmp_len = strlen(tmp_str);
bytes = tmp_len > count ? count : tmp_len;
if (copy_to_user(buffer, tmp_str, bytes)) bytes = -EFAULT;
else *offset += bytes;
#ifdef DEBUG
msleep(5000);
#endif
up_read(&foo_sem);
}
return bytes;
}
static ssize_t foo_write(struct file *, const char __user *buffer,
size_t count, loff_t * offset)
{
int bytes = -EINVAL;
if ((*offset + count) > PAGE_SIZE) bytes = -EFAULT;
else if (down_write_trylock(&foo_sem))
{
bytes = count;
if (copy_from_user(foo_msg, buffer, bytes)) bytes = -EINVAL;
#ifdef DEBUG
msleep(5000);
#endif
up_write(&foo_sem);
}
return bytes;
}
static const struct file_operations foo_fops = {
.owner = THIS_MODULE,
.read = foo_read,
.write = foo_write,
};
static int __init my_init(void)
{
init_rwsem(&foo_sem);
id_msg = kmalloc(12, GFP_KERNEL);
foo_msg = kmalloc(PAGE_SIZE, GFP_KERNEL);
strcpy(id_msg, "pouetpouet\n");
pr_info("Coucou le gens !!!!\n");
folder = debugfs_create_dir("eudyptula", NULL);
id_file = debugfs_create_file("id", 0666, folder, NULL, &id_fops);
debugfs_create_u64("jiffies", 0444, folder, &jiffies_64);
foo_file = debugfs_create_file("foo", 0664, folder, NULL, &foo_fops);
return 0;
}
static void __exit my_exit(void)
{
debugfs_remove_recursive(folder);
kfree(id_msg);
kfree(foo_msg);
pr_info("Tschuss !!!\n");
}
module_init(my_init);
module_exit(my_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("rick <rick@gnous.eu>");
MODULE_DESCRIPTION("Module pour tester le debugfs.");