307 lines
6.9 KiB
C
307 lines
6.9 KiB
C
/*
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* linux/drivers/char/raw.c
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*
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* Front-end raw character devices. These can be bound to any block
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* devices to provide genuine Unix raw character device semantics.
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*
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* We reserve minor number 0 for a control interface. ioctl()s on this
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* device are used to bind the other minor numbers to block devices.
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*/
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/major.h>
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#include <linux/blkdev.h>
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#include <linux/module.h>
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#include <linux/raw.h>
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#include <linux/capability.h>
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#include <linux/uio.h>
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#include <linux/cdev.h>
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#include <linux/device.h>
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#include <linux/mutex.h>
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#include <linux/smp_lock.h>
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#include <asm/uaccess.h>
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struct raw_device_data {
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struct block_device *binding;
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int inuse;
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};
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static struct class *raw_class;
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static struct raw_device_data raw_devices[MAX_RAW_MINORS];
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static DEFINE_MUTEX(raw_mutex);
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static const struct file_operations raw_ctl_fops; /* forward declaration */
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/*
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* Open/close code for raw IO.
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*
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* We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
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* point at the blockdev's address_space and set the file handle to use
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* O_DIRECT.
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*
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* Set the device's soft blocksize to the minimum possible. This gives the
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* finest possible alignment and has no adverse impact on performance.
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*/
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static int raw_open(struct inode *inode, struct file *filp)
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{
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const int minor = iminor(inode);
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struct block_device *bdev;
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int err;
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if (minor == 0) { /* It is the control device */
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filp->f_op = &raw_ctl_fops;
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return 0;
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}
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lock_kernel();
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mutex_lock(&raw_mutex);
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/*
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* All we need to do on open is check that the device is bound.
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*/
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bdev = raw_devices[minor].binding;
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err = -ENODEV;
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if (!bdev)
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goto out;
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igrab(bdev->bd_inode);
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err = blkdev_get(bdev, filp->f_mode, 0);
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if (err)
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goto out;
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err = bd_claim(bdev, raw_open);
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if (err)
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goto out1;
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err = set_blocksize(bdev, bdev_hardsect_size(bdev));
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if (err)
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goto out2;
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filp->f_flags |= O_DIRECT;
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filp->f_mapping = bdev->bd_inode->i_mapping;
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if (++raw_devices[minor].inuse == 1)
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filp->f_path.dentry->d_inode->i_mapping =
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bdev->bd_inode->i_mapping;
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filp->private_data = bdev;
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mutex_unlock(&raw_mutex);
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unlock_kernel();
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return 0;
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out2:
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bd_release(bdev);
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out1:
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blkdev_put(bdev);
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out:
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mutex_unlock(&raw_mutex);
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return err;
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}
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/*
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* When the final fd which refers to this character-special node is closed, we
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* make its ->mapping point back at its own i_data.
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*/
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static int raw_release(struct inode *inode, struct file *filp)
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{
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const int minor= iminor(inode);
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struct block_device *bdev;
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mutex_lock(&raw_mutex);
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bdev = raw_devices[minor].binding;
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if (--raw_devices[minor].inuse == 0) {
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/* Here inode->i_mapping == bdev->bd_inode->i_mapping */
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inode->i_mapping = &inode->i_data;
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inode->i_mapping->backing_dev_info = &default_backing_dev_info;
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}
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mutex_unlock(&raw_mutex);
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bd_release(bdev);
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blkdev_put(bdev);
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return 0;
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}
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/*
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* Forward ioctls to the underlying block device.
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*/
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static int
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raw_ioctl(struct inode *inode, struct file *filp,
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unsigned int command, unsigned long arg)
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{
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struct block_device *bdev = filp->private_data;
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return blkdev_ioctl(bdev->bd_inode, NULL, command, arg);
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}
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static void bind_device(struct raw_config_request *rq)
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{
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device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
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device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor), NULL,
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"raw%d", rq->raw_minor);
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}
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/*
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* Deal with ioctls against the raw-device control interface, to bind
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* and unbind other raw devices.
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*/
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static int raw_ctl_ioctl(struct inode *inode, struct file *filp,
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unsigned int command, unsigned long arg)
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{
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struct raw_config_request rq;
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struct raw_device_data *rawdev;
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int err = 0;
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switch (command) {
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case RAW_SETBIND:
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case RAW_GETBIND:
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/* First, find out which raw minor we want */
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if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
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err = -EFAULT;
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goto out;
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}
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if (rq.raw_minor <= 0 || rq.raw_minor >= MAX_RAW_MINORS) {
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err = -EINVAL;
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goto out;
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}
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rawdev = &raw_devices[rq.raw_minor];
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if (command == RAW_SETBIND) {
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dev_t dev;
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/*
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* This is like making block devices, so demand the
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* same capability
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*/
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if (!capable(CAP_SYS_ADMIN)) {
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err = -EPERM;
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goto out;
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}
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/*
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* For now, we don't need to check that the underlying
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* block device is present or not: we can do that when
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* the raw device is opened. Just check that the
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* major/minor numbers make sense.
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*/
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dev = MKDEV(rq.block_major, rq.block_minor);
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if ((rq.block_major == 0 && rq.block_minor != 0) ||
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MAJOR(dev) != rq.block_major ||
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MINOR(dev) != rq.block_minor) {
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err = -EINVAL;
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goto out;
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}
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mutex_lock(&raw_mutex);
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if (rawdev->inuse) {
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mutex_unlock(&raw_mutex);
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err = -EBUSY;
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goto out;
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}
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if (rawdev->binding) {
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bdput(rawdev->binding);
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module_put(THIS_MODULE);
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}
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if (rq.block_major == 0 && rq.block_minor == 0) {
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/* unbind */
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rawdev->binding = NULL;
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device_destroy(raw_class,
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MKDEV(RAW_MAJOR, rq.raw_minor));
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} else {
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rawdev->binding = bdget(dev);
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if (rawdev->binding == NULL)
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err = -ENOMEM;
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else {
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__module_get(THIS_MODULE);
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bind_device(&rq);
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}
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}
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mutex_unlock(&raw_mutex);
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} else {
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struct block_device *bdev;
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mutex_lock(&raw_mutex);
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bdev = rawdev->binding;
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if (bdev) {
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rq.block_major = MAJOR(bdev->bd_dev);
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rq.block_minor = MINOR(bdev->bd_dev);
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} else {
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rq.block_major = rq.block_minor = 0;
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}
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mutex_unlock(&raw_mutex);
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if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
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err = -EFAULT;
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goto out;
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}
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}
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break;
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default:
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err = -EINVAL;
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break;
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}
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out:
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return err;
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}
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static const struct file_operations raw_fops = {
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.read = do_sync_read,
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.aio_read = generic_file_aio_read,
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.write = do_sync_write,
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.aio_write = generic_file_aio_write_nolock,
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.open = raw_open,
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.release= raw_release,
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.ioctl = raw_ioctl,
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.owner = THIS_MODULE,
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};
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static const struct file_operations raw_ctl_fops = {
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.ioctl = raw_ctl_ioctl,
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.open = raw_open,
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.owner = THIS_MODULE,
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};
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static struct cdev raw_cdev;
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static int __init raw_init(void)
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{
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dev_t dev = MKDEV(RAW_MAJOR, 0);
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int ret;
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ret = register_chrdev_region(dev, MAX_RAW_MINORS, "raw");
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if (ret)
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goto error;
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cdev_init(&raw_cdev, &raw_fops);
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ret = cdev_add(&raw_cdev, dev, MAX_RAW_MINORS);
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if (ret) {
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kobject_put(&raw_cdev.kobj);
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goto error_region;
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}
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raw_class = class_create(THIS_MODULE, "raw");
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if (IS_ERR(raw_class)) {
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printk(KERN_ERR "Error creating raw class.\n");
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cdev_del(&raw_cdev);
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ret = PTR_ERR(raw_class);
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goto error_region;
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}
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device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
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return 0;
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error_region:
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unregister_chrdev_region(dev, MAX_RAW_MINORS);
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error:
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return ret;
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}
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static void __exit raw_exit(void)
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{
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device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
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class_destroy(raw_class);
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cdev_del(&raw_cdev);
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unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
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}
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module_init(raw_init);
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module_exit(raw_exit);
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MODULE_LICENSE("GPL");
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