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DEFINITIONS
This source file includes following definitions.
- scull_s_open
- scull_s_release
- scull_u_open
- scull_u_release
- scull_w_available
- scull_w_open
- scull_w_release
- scull_c_lookfor_device
- scull_c_open
- scull_c_release
- scull_access_setup
- scull_access_init
- scull_access_cleanup
/*
* access.c -- the files with access control on open
*
* Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
* Copyright (C) 2001 O'Reilly & Associates
*
* The source code in this file can be freely used, adapted,
* and redistributed in source or binary form, so long as an
* acknowledgment appears in derived source files. The citation
* should list that the code comes from the book "Linux Device
* Drivers" by Alessandro Rubini and Jonathan Corbet, published
* by O'Reilly & Associates. No warranty is attached;
* we cannot take responsibility for errors or fitness for use.
*
* $Id: access.c,v 1.17 2004/09/26 07:29:56 gregkh Exp $
*/
/* FIXME: cloned devices as a use for kobjects? */
#include <linux/kernel.h> /* printk() */
#include <linux/module.h>
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h> /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/types.h> /* size_t */
#include <linux/fcntl.h>
#include <linux/cdev.h>
#include <linux/tty.h>
#include <asm/atomic.h>
#include <linux/list.h>
#include "scull.h" /* local definitions */
static dev_t scull_a_firstdev; /* Where our range begins */
/*
* These devices fall back on the main scull operations. They only
* differ in the implementation of open() and close()
*/
/************************************************************************
*
* The first device is the single-open one,
* it has an hw structure and an open count
*/
static struct scull_dev scull_s_device;
static atomic_t scull_s_available = ATOMIC_INIT(1);
static int scull_s_open(struct inode *inode, struct file *filp)
{
struct scull_dev *dev = &scull_s_device; /* device information */
if (! atomic_dec_and_test (&scull_s_available)) {
atomic_inc(&scull_s_available);
return -EBUSY; /* already open */
}
/* then, everything else is copied from the bare scull device */
if ( (filp->f_flags & O_ACCMODE) == O_WRONLY)
scull_trim(dev);
filp->private_data = dev;
return 0; /* success */
}
static int scull_s_release(struct inode *inode, struct file *filp)
{
atomic_inc(&scull_s_available); /* release the device */
return 0;
}
/*
* The other operations for the single-open device come from the bare device
*/
struct file_operations scull_sngl_fops = {
.owner = THIS_MODULE,
.llseek = scull_llseek,
.read = scull_read,
.write = scull_write,
.ioctl = scull_ioctl,
.open = scull_s_open,
.release = scull_s_release,
};
/************************************************************************
*
* Next, the "uid" device. It can be opened multiple times by the
* same user, but access is denied to other users if the device is open
*/
static struct scull_dev scull_u_device;
static int scull_u_count; /* initialized to 0 by default */
static uid_t scull_u_owner; /* initialized to 0 by default */
static spinlock_t scull_u_lock = SPIN_LOCK_UNLOCKED;
static int scull_u_open(struct inode *inode, struct file *filp)
{
struct scull_dev *dev = &scull_u_device; /* device information */
spin_lock(&scull_u_lock);
if (scull_u_count &&
(scull_u_owner != current->uid) && /* allow user */
(scull_u_owner != current->euid) && /* allow whoever did su */
!capable(CAP_DAC_OVERRIDE)) { /* still allow root */
spin_unlock(&scull_u_lock);
return -EBUSY; /* -EPERM would confuse the user */
}
if (scull_u_count == 0)
scull_u_owner = current->uid; /* grab it */
scull_u_count++;
spin_unlock(&scull_u_lock);
/* then, everything else is copied from the bare scull device */
if ((filp->f_flags & O_ACCMODE) == O_WRONLY)
scull_trim(dev);
filp->private_data = dev;
return 0; /* success */
}
static int scull_u_release(struct inode *inode, struct file *filp)
{
spin_lock(&scull_u_lock);
scull_u_count--; /* nothing else */
spin_unlock(&scull_u_lock);
return 0;
}
/*
* The other operations for the device come from the bare device
*/
struct file_operations scull_user_fops = {
.owner = THIS_MODULE,
.llseek = scull_llseek,
.read = scull_read,
.write = scull_write,
.ioctl = scull_ioctl,
.open = scull_u_open,
.release = scull_u_release,
};
/************************************************************************
*
* Next, the device with blocking-open based on uid
*/
static struct scull_dev scull_w_device;
static int scull_w_count; /* initialized to 0 by default */
static uid_t scull_w_owner; /* initialized to 0 by default */
static DECLARE_WAIT_QUEUE_HEAD(scull_w_wait);
static spinlock_t scull_w_lock = SPIN_LOCK_UNLOCKED;
static inline int scull_w_available(void)
{
return scull_w_count == 0 ||
scull_w_owner == current->uid ||
scull_w_owner == current->euid ||
capable(CAP_DAC_OVERRIDE);
}
static int scull_w_open(struct inode *inode, struct file *filp)
{
struct scull_dev *dev = &scull_w_device; /* device information */
spin_lock(&scull_w_lock);
while (! scull_w_available()) {
spin_unlock(&scull_w_lock);
if (filp->f_flags & O_NONBLOCK) return -EAGAIN;
if (wait_event_interruptible (scull_w_wait, scull_w_available()))
return -ERESTARTSYS; /* tell the fs layer to handle it */
spin_lock(&scull_w_lock);
}
if (scull_w_count == 0)
scull_w_owner = current->uid; /* grab it */
scull_w_count++;
spin_unlock(&scull_w_lock);
/* then, everything else is copied from the bare scull device */
if ((filp->f_flags & O_ACCMODE) == O_WRONLY)
scull_trim(dev);
filp->private_data = dev;
return 0; /* success */
}
static int scull_w_release(struct inode *inode, struct file *filp)
{
int temp;
spin_lock(&scull_w_lock);
scull_w_count--;
temp = scull_w_count;
spin_unlock(&scull_w_lock);
if (temp == 0)
wake_up_interruptible_sync(&scull_w_wait); /* awake other uid's */
return 0;
}
/*
* The other operations for the device come from the bare device
*/
struct file_operations scull_wusr_fops = {
.owner = THIS_MODULE,
.llseek = scull_llseek,
.read = scull_read,
.write = scull_write,
.ioctl = scull_ioctl,
.open = scull_w_open,
.release = scull_w_release,
};
/************************************************************************
*
* Finally the `cloned' private device. This is trickier because it
* involves list management, and dynamic allocation.
*/
/* The clone-specific data structure includes a key field */
struct scull_listitem {
struct scull_dev device;
dev_t key;
struct list_head list;
};
/* The list of devices, and a lock to protect it */
static LIST_HEAD(scull_c_list);
static spinlock_t scull_c_lock = SPIN_LOCK_UNLOCKED;
/* A placeholder scull_dev which really just holds the cdev stuff. */
static struct scull_dev scull_c_device;
/* Look for a device or create one if missing */
static struct scull_dev *scull_c_lookfor_device(dev_t key)
{
struct scull_listitem *lptr;
list_for_each_entry(lptr, &scull_c_list, list) {
if (lptr->key == key)
return &(lptr->device);
}
/* not found */
lptr = kmalloc(sizeof(struct scull_listitem), GFP_KERNEL);
if (!lptr)
return NULL;
/* initialize the device */
memset(lptr, 0, sizeof(struct scull_listitem));
lptr->key = key;
scull_trim(&(lptr->device)); /* initialize it */
init_MUTEX(&(lptr->device.sem));
/* place it in the list */
list_add(&lptr->list, &scull_c_list);
return &(lptr->device);
}
static int scull_c_open(struct inode *inode, struct file *filp)
{
struct scull_dev *dev;
dev_t key;
if (!current->signal->tty) {
PDEBUG("Process \"%s\" has no ctl tty\n", current->comm);
return -EINVAL;
}
key = tty_devnum(current->signal->tty);
/* look for a scullc device in the list */
spin_lock(&scull_c_lock);
dev = scull_c_lookfor_device(key);
spin_unlock(&scull_c_lock);
if (!dev)
return -ENOMEM;
/* then, everything else is copied from the bare scull device */
if ( (filp->f_flags & O_ACCMODE) == O_WRONLY)
scull_trim(dev);
filp->private_data = dev;
return 0; /* success */
}
static int scull_c_release(struct inode *inode, struct file *filp)
{
/*
* Nothing to do, because the device is persistent.
* A `real' cloned device should be freed on last close
*/
return 0;
}
/*
* The other operations for the device come from the bare device
*/
struct file_operations scull_priv_fops = {
.owner = THIS_MODULE,
.llseek = scull_llseek,
.read = scull_read,
.write = scull_write,
.ioctl = scull_ioctl,
.open = scull_c_open,
.release = scull_c_release,
};
/************************************************************************
*
* And the init and cleanup functions come last
*/
static struct scull_adev_info {
char *name;
struct scull_dev *sculldev;
struct file_operations *fops;
} scull_access_devs[] = {
{ "scullsingle", &scull_s_device, &scull_sngl_fops },
{ "sculluid", &scull_u_device, &scull_user_fops },
{ "scullwuid", &scull_w_device, &scull_wusr_fops },
{ "sullpriv", &scull_c_device, &scull_priv_fops }
};
#define SCULL_N_ADEVS 4
/*
* Set up a single device.
*/
static void scull_access_setup (dev_t devno, struct scull_adev_info *devinfo)
{
struct scull_dev *dev = devinfo->sculldev;
int err;
/* Initialize the device structure */
dev->quantum = scull_quantum;
dev->qset = scull_qset;
init_MUTEX(&dev->sem);
/* Do the cdev stuff. */
cdev_init(&dev->cdev, devinfo->fops);
kobject_set_name(&dev->cdev.kobj, devinfo->name);
dev->cdev.owner = THIS_MODULE;
err = cdev_add (&dev->cdev, devno, 1);
/* Fail gracefully if need be */
if (err) {
printk(KERN_NOTICE "Error %d adding %s\n", err, devinfo->name);
kobject_put(&dev->cdev.kobj);
} else
printk(KERN_NOTICE "%s registered at %x\n", devinfo->name, devno);
}
int scull_access_init(dev_t firstdev)
{
int result, i;
/* Get our number space */
result = register_chrdev_region (firstdev, SCULL_N_ADEVS, "sculla");
if (result < 0) {
printk(KERN_WARNING "sculla: device number registration failed\n");
return 0;
}
scull_a_firstdev = firstdev;
/* Set up each device. */
for (i = 0; i < SCULL_N_ADEVS; i++)
scull_access_setup (firstdev + i, scull_access_devs + i);
return SCULL_N_ADEVS;
}
/*
* This is called by cleanup_module or on failure.
* It is required to never fail, even if nothing was initialized first
*/
void scull_access_cleanup(void)
{
struct scull_listitem *lptr, *next;
int i;
/* Clean up the static devs */
for (i = 0; i < SCULL_N_ADEVS; i++) {
struct scull_dev *dev = scull_access_devs[i].sculldev;
cdev_del(&dev->cdev);
scull_trim(scull_access_devs[i].sculldev);
}
/* And all the cloned devices */
list_for_each_entry_safe(lptr, next, &scull_c_list, list) {
list_del(&lptr->list);
scull_trim(&(lptr->device));
kfree(lptr);
}
/* Free up our number space */
unregister_chrdev_region(scull_a_firstdev, SCULL_N_ADEVS);
return;
}