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32 results

raw.c

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  • raw.c 6.96 KiB
    /*
     * 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/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/smp_lock.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[MAX_RAW_MINORS];
    static DEFINE_MUTEX(raw_mutex);
    static const struct file_operations raw_ctl_fops; /* forward declaration */
    
    /*
     * 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;
    	}
    
    	lock_kernel();
    	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);
    	if (err)
    		goto out;
    	err = bd_claim(bdev, raw_open);
    	if (err)
    		goto out1;
    	err = set_blocksize(bdev, bdev_hardsect_size(bdev));
    	if (err)
    		goto out2;
    	filp->f_flags |= O_DIRECT;
    	filp->f_mapping = bdev->bd_inode->i_mapping;
    	if (++raw_devices[minor].inuse == 1)
    		filp->f_path.dentry->d_inode->i_mapping =
    			bdev->bd_inode->i_mapping;
    	filp->private_data = bdev;
    	mutex_unlock(&raw_mutex);
    	unlock_kernel();
    	return 0;
    
    out2:
    	bd_release(bdev);
    out1:
    	blkdev_put(bdev, filp->f_mode);
    out:
    	mutex_unlock(&raw_mutex);
    	unlock_kernel();
    	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;
    		inode->i_mapping->backing_dev_info = &default_backing_dev_info;
    	}
    	mutex_unlock(&raw_mutex);
    
    	bd_release(bdev);
    	blkdev_put(bdev, filp->f_mode);
    	return 0;
    }
    
    /*
     * Forward ioctls to the underlying block device.
     */
    static int
    raw_ioctl(struct inode *inode, struct file *filp,
    		  unsigned int command, unsigned long arg)
    {
    	struct block_device *bdev = filp->private_data;
    
    	return blkdev_ioctl(bdev, 0, command, arg);
    }
    
    static void bind_device(struct raw_config_request *rq)
    {
    	device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
    	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor), NULL,
    		      "raw%d", rq->raw_minor);
    }
    
    /*
     * Deal with ioctls against the raw-device control interface, to bind
     * and unbind other raw devices.
     */
    static int raw_ctl_ioctl(struct inode *inode, struct file *filp,
    			unsigned int command, unsigned long arg)
    {
    	struct raw_config_request rq;
    	struct raw_device_data *rawdev;
    	int err = 0;
    
    	switch (command) {
    	case RAW_SETBIND:
    	case RAW_GETBIND:
    
    		/* First, find out which raw minor we want */
    
    		if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
    			err = -EFAULT;
    			goto out;
    		}
    
    		if (rq.raw_minor <= 0 || rq.raw_minor >= MAX_RAW_MINORS) {
    			err = -EINVAL;
    			goto out;
    		}
    		rawdev = &raw_devices[rq.raw_minor];
    
    		if (command == RAW_SETBIND) {
    			dev_t dev;
    
    			/*
    			 * This is like making block devices, so demand the
    			 * same capability
    			 */
    			if (!capable(CAP_SYS_ADMIN)) {
    				err = -EPERM;
    				goto out;
    			}
    
    			/*
    			 * 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.
    			 */
    
    			dev = MKDEV(rq.block_major, rq.block_minor);
    			if ((rq.block_major == 0 && rq.block_minor != 0) ||
    					MAJOR(dev) != rq.block_major ||
    					MINOR(dev) != rq.block_minor) {
    				err = -EINVAL;
    				goto out;
    			}
    
    			mutex_lock(&raw_mutex);
    			if (rawdev->inuse) {
    				mutex_unlock(&raw_mutex);
    				err = -EBUSY;
    				goto out;
    			}
    			if (rawdev->binding) {
    				bdput(rawdev->binding);
    				module_put(THIS_MODULE);
    			}
    			if (rq.block_major == 0 && rq.block_minor == 0) {
    				/* unbind */
    				rawdev->binding = NULL;
    				device_destroy(raw_class,
    						MKDEV(RAW_MAJOR, rq.raw_minor));
    			} else {
    				rawdev->binding = bdget(dev);
    				if (rawdev->binding == NULL)
    					err = -ENOMEM;
    				else {
    					__module_get(THIS_MODULE);
    					bind_device(&rq);
    				}
    			}
    			mutex_unlock(&raw_mutex);
    		} else {
    			struct block_device *bdev;
    
    			mutex_lock(&raw_mutex);
    			bdev = rawdev->binding;
    			if (bdev) {
    				rq.block_major = MAJOR(bdev->bd_dev);
    				rq.block_minor = MINOR(bdev->bd_dev);
    			} else {
    				rq.block_major = rq.block_minor = 0;
    			}
    			mutex_unlock(&raw_mutex);
    			if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
    				err = -EFAULT;
    				goto out;
    			}
    		}
    		break;
    	default:
    		err = -EINVAL;
    		break;
    	}
    out:
    	return err;
    }
    
    static const struct file_operations raw_fops = {
    	.read	=	do_sync_read,
    	.aio_read = 	generic_file_aio_read,
    	.write	=	do_sync_write,
    	.aio_write = 	generic_file_aio_write_nolock,
    	.open	=	raw_open,
    	.release=	raw_release,
    	.ioctl	=	raw_ioctl,
    	.owner	=	THIS_MODULE,
    };
    
    static const struct file_operations raw_ctl_fops = {
    	.ioctl	=	raw_ctl_ioctl,
    	.open	=	raw_open,
    	.owner	=	THIS_MODULE,
    };
    
    static struct cdev raw_cdev;
    
    static int __init raw_init(void)
    {
    	dev_t dev = MKDEV(RAW_MAJOR, 0);
    	int ret;
    
    	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) {
    		kobject_put(&raw_cdev.kobj);
    		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;
    	}
    	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
    
    	return 0;
    
    error_region:
    	unregister_chrdev_region(dev, MAX_RAW_MINORS);
    error:
    	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");