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/*-
* GPL LICENSE SUMMARY
*
* Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
* The full GNU General Public License is included in this distribution
* in the file called LICENSE.GPL.
*
* Contact Information:
* Intel Corporation
*/
#include <linux/eventfd.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/rcupdate.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/mmu_context.h>
#include <linux/sched.h>
#include <asm/mmu_context.h>
#include <linux/fdtable.h>
#include "eventfd_link.h"
/*
* get_files_struct is copied from fs/file.c
*/
struct files_struct *
get_files_struct(struct task_struct *task)
{
struct files_struct *files;
task_lock(task);
files = task->files;
if (files)
atomic_inc(&files->count);
task_unlock(task);
return files;
}
/*
* put_files_struct is extracted from fs/file.c
*/
void
put_files_struct(struct files_struct *files)
{
if (atomic_dec_and_test(&files->count))
BUG();
}
static long
eventfd_link_ioctl(struct file *f, unsigned int ioctl, unsigned long arg)
{
void __user *argp = (void __user *) arg;
struct task_struct *task_target = NULL;
struct file *file;
struct files_struct *files;
struct fdtable *fdt;
struct eventfd_copy eventfd_copy;
switch (ioctl) {
case EVENTFD_COPY:
if (copy_from_user(&eventfd_copy, argp,
sizeof(struct eventfd_copy)))
return -EFAULT;
/*
* Find the task struct for the target pid
*/
task_target =
pid_task(find_vpid(eventfd_copy.target_pid), PIDTYPE_PID);
if (task_target == NULL) {
pr_debug("Failed to get mem ctx for target pid\n");
return -EFAULT;
}
files = get_files_struct(current);
if (files == NULL) {
pr_debug("Failed to get files struct\n");
return -EFAULT;
}
rcu_read_lock();
file = fcheck_files(files, eventfd_copy.source_fd);
if (file) {
if (file->f_mode & FMODE_PATH ||
!atomic_long_inc_not_zero(&file->f_count))
file = NULL;
}
rcu_read_unlock();
put_files_struct(files);
if (file == NULL) {
pr_debug("Failed to get file from source pid\n");
return 0;
}
/*
* Release the existing eventfd in the source process
*/
spin_lock(&files->file_lock);
filp_close(file, files);
fdt = files_fdtable(files);
fdt->fd[eventfd_copy.source_fd] = NULL;
spin_unlock(&files->file_lock);
/*
* Find the file struct associated with the target fd.
*/
files = get_files_struct(task_target);
if (files == NULL) {
pr_debug("Failed to get files struct\n");
return -EFAULT;
}
rcu_read_lock();
file = fcheck_files(files, eventfd_copy.target_fd);
if (file) {
if (file->f_mode & FMODE_PATH ||
!atomic_long_inc_not_zero(&file->f_count))
file = NULL;
}
rcu_read_unlock();
put_files_struct(files);
if (file == NULL) {
pr_debug("Failed to get file from target pid\n");
return 0;
}
/*
* Install the file struct from the target process into the
* file desciptor of the source process,
*/
fd_install(eventfd_copy.source_fd, file);
return 0;
default:
return -ENOIOCTLCMD;
}
}
static const struct file_operations eventfd_link_fops = {
.owner = THIS_MODULE,
.unlocked_ioctl = eventfd_link_ioctl,
};
static struct miscdevice eventfd_link_misc = {
.name = "eventfd-link",
.fops = &eventfd_link_fops,
};
static int __init
eventfd_link_init(void)
{
return misc_register(&eventfd_link_misc);
}
module_init(eventfd_link_init);
static void __exit
eventfd_link_exit(void)
{
misc_deregister(&eventfd_link_misc);
}
module_exit(eventfd_link_exit);
MODULE_VERSION("0.0.1");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Anthony Fee");
MODULE_DESCRIPTION("Link eventfd");
MODULE_ALIAS("devname:eventfd-link");
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