- 根目录:
- drivers
- char
- raw.c
/*
* linux/drivers/char/raw.c
*
* Front-end raw character devices. These can be bound to any block
* devices to provide genuine Unix raw character device semantics.
*
* We reserve minor number 0 for a control interface. ioctl()s on this
* device are used to bind the other minor numbers to block devices.
*/
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/major.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/module.h>
#include <linux/raw.h>
#include <linux/capability.h>
#include <linux/uio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/gfp.h>
#include <linux/compat.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>
struct raw_device_data {
struct block_device *binding;
int inuse;
};
static struct class *raw_class;
static struct raw_device_data *raw_devices;
static DEFINE_MUTEX(raw_mutex);
static const struct file_operations raw_ctl_fops; /* forward declaration */
static int max_raw_minors = MAX_RAW_MINORS;
module_param(max_raw_minors, int, 0);
MODULE_PARM_DESC(max_raw_minors, "Maximum number of raw devices (1-65536)");
/*
* Open/close code for raw IO.
*
* We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
* point at the blockdev's address_space and set the file handle to use
* O_DIRECT.
*
* Set the device's soft blocksize to the minimum possible. This gives the
* finest possible alignment and has no adverse impact on performance.
*/
static int raw_open(struct inode *inode, struct file *filp)
{
const int minor = iminor(inode);
struct block_device *bdev;
int err;
if (minor == 0) { /* It is the control device */
filp->f_op = &raw_ctl_fops;
return 0;
}
mutex_lock(&raw_mutex);
/*
* All we need to do on open is check that the device is bound.
*/
bdev = raw_devices[minor].binding;
err = -ENODEV;
if (!bdev)
goto out;
igrab(bdev->bd_inode);
err = blkdev_get(bdev, filp->f_mode | FMODE_EXCL, raw_open);
if (err)
goto out;
err = set_blocksize(bdev, bdev_logical_block_size(bdev));
if (err)
goto out1;
filp->f_flags |= O_DIRECT;
filp->f_mapping = bdev->bd_inode->i_mapping;
if (++raw_devices[minor].inuse == 1)
file_inode(filp)->i_mapping =
bdev->bd_inode->i_mapping;
filp->private_data = bdev;
mutex_unlock(&raw_mutex);
return 0;
out1:
blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
out:
mutex_unlock(&raw_mutex);
return err;
}
/*
* When the final fd which refers to this character-special node is closed, we
* make its ->mapping point back at its own i_data.
*/
static int raw_release(struct inode *inode, struct file *filp)
{
const int minor= iminor(inode);
struct block_device *bdev;
mutex_lock(&raw_mutex);
bdev = raw_devices[minor].binding;
if (--raw_devices[minor].inuse == 0)
/* Here inode->i_mapping == bdev->bd_inode->i_mapping */
inode->i_mapping = &inode->i_data;
mutex_unlock(&raw_mutex);
blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
return 0;
}
/*
* Forward ioctls to the underlying block device.
*/
static long
raw_ioctl(struct file *filp, unsigned int command, unsigned long arg)
{
struct block_device *bdev = filp->private_data;
return blkdev_ioctl(bdev, 0, command, arg);
}
static int bind_set(int number, u64 major, u64 minor)
{
dev_t dev = MKDEV(major, minor);
struct raw_device_data *rawdev;
int err = 0;
if (number <= 0 || number >= max_raw_minors)
return -EINVAL;
if (MAJOR(dev) != major || MINOR(dev) != minor)
return -EINVAL;
rawdev = &raw_devices[number];
/*
* This is like making block devices, so demand the
* same capability
*/
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
/*
* For now, we don't need to check that the underlying
* block device is present or not: we can do that when
* the raw device is opened. Just check that the
* major/minor numbers make sense.
*/
if (MAJOR(dev) == 0 && dev != 0)
return -EINVAL;
mutex_lock(&raw_mutex);
if (rawdev->inuse) {
mutex_unlock(&raw_mutex);
return -EBUSY;
}
if (rawdev->binding) {
bdput(rawdev->binding);
module_put(THIS_MODULE);
}
if (!dev) {
/* unbind */
rawdev->binding = NULL;
device_destroy(raw_class, MKDEV(RAW_MAJOR, number));
} else {
rawdev->binding = bdget(dev);
if (rawdev->binding == NULL) {
err = -ENOMEM;
} else {
dev_t raw = MKDEV(RAW_MAJOR, number);
__module_get(THIS_MODULE);
device_destroy(raw_class, raw);
device_create(raw_class, NULL, raw, NULL,
"raw%d", number);
}
}
mutex_unlock(&raw_mutex);
return err;
}
static int bind_get(int number, dev_t *dev)
{
struct raw_device_data *rawdev;
struct block_device *bdev;
if (number <= 0 || number >= max_raw_minors)
return -EINVAL;
rawdev = &raw_devices[number];
mutex_lock(&raw_mutex);
bdev = rawdev->binding;
*dev = bdev ? bdev->bd_dev : 0;
mutex_unlock(&raw_mutex);
return 0;
}
/*
* Deal with ioctls against the raw-device control interface, to bind
* and unbind other raw devices.
*/
static long raw_ctl_ioctl(struct file *filp, unsigned int command,
unsigned long arg)
{
struct raw_config_request rq;
dev_t dev;
int err;
switch (command) {
case RAW_SETBIND:
if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
return -EFAULT;
return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
case RAW_GETBIND:
if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
return -EFAULT;
err = bind_get(rq.raw_minor, &dev);
if (err)
return err;
rq.block_major = MAJOR(dev);
rq.block_minor = MINOR(dev);
if (copy_to_user((void __user *)arg, &rq, sizeof(rq)))
return -EFAULT;
return 0;
}
return -EINVAL;
}
#ifdef CONFIG_COMPAT
struct raw32_config_request {
compat_int_t raw_minor;
compat_u64 block_major;
compat_u64 block_minor;
};
static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct raw32_config_request __user *user_req = compat_ptr(arg);
struct raw32_config_request rq;
dev_t dev;
int err = 0;
switch (cmd) {
case RAW_SETBIND:
if (copy_from_user(&rq, user_req, sizeof(rq)))
return -EFAULT;
return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
case RAW_GETBIND:
if (copy_from_user(&rq, user_req, sizeof(rq)))
return -EFAULT;
err = bind_get(rq.raw_minor, &dev);
if (err)
return err;
rq.block_major = MAJOR(dev);
rq.block_minor = MINOR(dev);
if (copy_to_user(user_req, &rq, sizeof(rq)))
return -EFAULT;
return 0;
}
return -EINVAL;
}
#endif
static const struct file_operations raw_fops = {
.read_iter = blkdev_read_iter,
.write_iter = blkdev_write_iter,
.fsync = blkdev_fsync,
.open = raw_open,
.release = raw_release,
.unlocked_ioctl = raw_ioctl,
.llseek = default_llseek,
.owner = THIS_MODULE,
};
static const struct file_operations raw_ctl_fops = {
.unlocked_ioctl = raw_ctl_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = raw_ctl_compat_ioctl,
#endif
.open = raw_open,
.owner = THIS_MODULE,
.llseek = noop_llseek,
};
static struct cdev raw_cdev;
static char *raw_devnode(struct device *dev, umode_t *mode)
{
return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev));
}
static int __init raw_init(void)
{
dev_t dev = MKDEV(RAW_MAJOR, 0);
int ret;
if (max_raw_minors < 1 || max_raw_minors > 65536) {
printk(KERN_WARNING "raw: invalid max_raw_minors (must be"
" between 1 and 65536), using %d\n", MAX_RAW_MINORS);
max_raw_minors = MAX_RAW_MINORS;
}
raw_devices = vzalloc(sizeof(struct raw_device_data) * max_raw_minors);
if (!raw_devices) {
printk(KERN_ERR "Not enough memory for raw device structures\n");
ret = -ENOMEM;
goto error;
}
ret = register_chrdev_region(dev, max_raw_minors, "raw");
if (ret)
goto error;
cdev_init(&raw_cdev, &raw_fops);
ret = cdev_add(&raw_cdev, dev, max_raw_minors);
if (ret) {
goto error_region;
}
raw_class = class_create(THIS_MODULE, "raw");
if (IS_ERR(raw_class)) {
printk(KERN_ERR "Error creating raw class.\n");
cdev_del(&raw_cdev);
ret = PTR_ERR(raw_class);
goto error_region;
}
raw_class->devnode = raw_devnode;
device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
return 0;
error_region:
unregister_chrdev_region(dev, max_raw_minors);
error:
vfree(raw_devices);
return ret;
}
static void __exit raw_exit(void)
{
device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
class_destroy(raw_class);
cdev_del(&raw_cdev);
unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), max_raw_minors);
}
module_init(raw_init);
module_exit(raw_exit);
MODULE_LICENSE("GPL");