/* * 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 <linux/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; bdgrab(bdev); 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");