J'ai eu le même problème et l'ai résolu en créant un module de noyau qui se coince dans l'état D.
Comme je n'ai aucune expérience dans les modules, j'ai pris le code de ce turorial avec quelques modifications trouvées quelque part esle .
Le résultat est un périphérique sur / dev / memory qui reste bloqué en lecture mais peut être réveillé en écrivant dessus (il a besoin de deux écritures, je ne sais pas pourquoi mais je m'en fiche).
Pour l'utiliser simplement:
# make
# make mknod
# make install
# cat /dev/memory # this gets blocked
Pour débloquer, depuis un autre terminal:
# echo -n a > /dev/memory
# echo -n a > /dev/memory
Makefile:
obj-m += memory.o
all:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
install:
sudo insmod memory.ko
uninstall:
sudo rmmod memory
mknod:
sudo mknod /dev/memory c 60 0
sudo chmod 666 /dev/memory
Code pour memory.c:
/* Necessary includes for device drivers */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h> /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/types.h> /* size_t */
#include <linux/proc_fs.h>
#include <linux/fcntl.h> /* O_ACCMODE */
#include <asm/uaccess.h> /* copy_from/to_user */
#include <linux/sched.h>
MODULE_LICENSE("Dual BSD/GPL");
/* Declaration of memory.c functions */
int memory_open(struct inode *inode, struct file *filp);
int memory_release(struct inode *inode, struct file *filp);
ssize_t memory_read(struct file *filp, char *buf, size_t count, loff_t *f_pos);
ssize_t memory_write(struct file *filp, char *buf, size_t count, loff_t *f_pos);
void memory_exit(void);
int memory_init(void);
/* Structure that declares the usual file */
/* access functions */
ssize_t memory_write( struct file *filp, char *buf, size_t count, loff_t *f_pos);
ssize_t memory_read(struct file *filp, char *buf, size_t count, loff_t *f_pos);
int memory_open(struct inode *inode, struct file *filp);
int memory_release(struct inode *inode, struct file *filp);
struct file_operations memory_fops = {
.read = memory_read,
.write = memory_write,
.open = memory_open,
.release = memory_release
};
/* Declaration of the init and exit functions */
module_init(memory_init);
module_exit(memory_exit);
/* Global variables of the driver */
/* Major number */
int memory_major = 60;
/* Buffer to store data */
char *memory_buffer;
int memory_init(void) {
int result;
/* Registering device */
result = register_chrdev(memory_major, "memory", &memory_fops);
if (result < 0) {
printk(
"<1>memory: cannot obtain major number %d\n", memory_major);
return result;
}
/* Allocating memory for the buffer */
memory_buffer = kmalloc(1, GFP_KERNEL);
if (!memory_buffer) {
result = -ENOMEM;
goto fail;
}
memset(memory_buffer, 0, 1);
printk("<1>Inserting memory module\n");
return 0;
fail:
memory_exit();
return result;
}
void memory_exit(void) {
/* Freeing the major number */
unregister_chrdev(memory_major, "memory");
/* Freeing buffer memory */
if (memory_buffer) {
kfree(memory_buffer);
}
printk("<1>Removing memory module\n");
}
int memory_open(struct inode *inode, struct file *filp) {
/* Success */
return 0;
}
int memory_release(struct inode *inode, struct file *filp) {
/* Success */
return 0;
}
static DECLARE_WAIT_QUEUE_HEAD(wq);
static volatile int flag = 0;
ssize_t memory_read(struct file *filp, char *buf,
size_t count, loff_t *f_pos) {
printk("<1>going to sleep\n");
flag = 0;
//wait_event_interruptible(wq, flag != 0);
wait_event(wq, flag != 0);
printk("<1>Reading from memory module\n");
/* Transfering data to user space */
copy_to_user(buf,memory_buffer,1);
/* Changing reading position as best suits */
if (*f_pos == 0) {
*f_pos+=1;
return 1;
} else {
return 0;
}
}
ssize_t memory_write( struct file *filp, char *buf,
size_t count, loff_t *f_pos) {
char *tmp;
printk("<1>wake someone up\n");
flag = 1;
//wake_up_interruptible(&wq);
wake_up(&wq);
printk("<1>Writting to memory module\n");
tmp=buf+count-1;
copy_from_user(memory_buffer,tmp,1);
return 1;
}