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#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/wait.h>
#include <linux/module.h>
#include <linux/version.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Renzo Davoli");
MODULE_DESCRIPTION("vpoll: sythesize events for select/poll/epoll");
MODULE_VERSION("0.01");
#define NAME "vpoll"
#define VPOLL_IOC_MAGIC '^'
#define VPOLL_IO_ADDEVENTS _IO(VPOLL_IOC_MAGIC, 1)
#define VPOLL_IO_DELEVENTS _IO(VPOLL_IOC_MAGIC, 2)
#define VPOLL_IO_SETEVENTS _IO(VPOLL_IOC_MAGIC, 3)
#define EPOLLALLMASK ((__force __poll_t)0x0fffffff)
static int major = -1;
static struct cdev mycdev;
static struct class *vpoll_class = NULL;
struct vpoll_data {
wait_queue_head_t wqh;
__poll_t events;
};
static int vpoll_open(struct inode *inode, struct file *file) {
struct vpoll_data *vpoll_data;
vpoll_data = kmalloc(sizeof(struct vpoll_data), GFP_KERNEL);
if (!vpoll_data)
return -ENOMEM;
vpoll_data->events = 0;
init_waitqueue_head(&vpoll_data->wqh);
file->private_data = vpoll_data;
return 0;
}
static int vpoll_release(struct inode *inode, struct file *file) {
struct vpoll_data *vpoll_data = file->private_data;
kfree(vpoll_data);
return 0;
}
static long vpoll_ioctl(struct file *file, unsigned int cmd, unsigned long arg) {
struct vpoll_data *vpoll_data = file->private_data;
__poll_t events = arg & EPOLLALLMASK;
long res = 0;
spin_lock_irq(&vpoll_data->wqh.lock);
switch(cmd) {
case VPOLL_IO_ADDEVENTS:
vpoll_data->events |= events;
break;
case VPOLL_IO_DELEVENTS:
vpoll_data->events &= ~events;
break;
case VPOLL_IO_SETEVENTS:
vpoll_data->events = events;
break;
default:
res = -EINVAL;
}
if (res >= 0) {
res = vpoll_data->events;
if (waitqueue_active(&vpoll_data->wqh))
wake_up_locked_poll(&vpoll_data->wqh, vpoll_data->events);
}
spin_unlock_irq(&vpoll_data->wqh.lock);
return res;
}
static __poll_t vpoll_poll(struct file *file, struct poll_table_struct *wait)
{
struct vpoll_data *vpoll_data = file->private_data;
poll_wait(file, &vpoll_data->wqh, wait);
return READ_ONCE(vpoll_data->events);
}
static const struct file_operations fops = {
.owner = THIS_MODULE,
.open = vpoll_open,
.release = vpoll_release,
.unlocked_ioctl = vpoll_ioctl,
.poll = vpoll_poll,
};
#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 2, 0)
static char *vpoll_devnode(struct device *dev, umode_t *mode)
#else
static char *vpoll_devnode(const struct device *dev, umode_t *mode)
#endif
{
if (!mode)
return NULL;
*mode = 0666;
return NULL;
}
#if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 4, 0)
#define vpoll_class_create() class_create(NAME)
#else
#define vpoll_class_create() class_create(THIS_MODULE, NAME)
#endif
static int myinit(void)
{
int ret;
struct device *dev;
if ((ret = alloc_chrdev_region(&major, 0, 1, NAME)) < 0)
return ret;
vpoll_class = vpoll_class_create();
if (IS_ERR(vpoll_class)) {
ret = PTR_ERR(vpoll_class);
goto error_unregister_chrdev_region;
}
vpoll_class->devnode = vpoll_devnode;
dev = device_create(vpoll_class, NULL, major, NULL, NAME);
if (IS_ERR(dev)) {
ret = PTR_ERR(dev);
goto error_class_destroy;
}
cdev_init(&mycdev, &fops);
if ((ret = cdev_add(&mycdev, major, 1)) < 0)
goto error_device_destroy;
printk(KERN_INFO NAME ": loaded\n");
return 0;
error_device_destroy:
device_destroy(vpoll_class, major);
error_class_destroy:
class_destroy(vpoll_class);
error_unregister_chrdev_region:
unregister_chrdev_region(major, 1);
return ret;
}
static void myexit(void)
{
device_destroy(vpoll_class, major);
cdev_del(&mycdev);
class_destroy(vpoll_class);
unregister_chrdev_region(major, 1);
printk(KERN_INFO NAME ": unloaded\n");
}
module_init(myinit)
module_exit(myexit)
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