diff options
Diffstat (limited to 'drivers/char/raw.c')
| -rw-r--r-- | drivers/char/raw.c | 369 |
1 files changed, 369 insertions, 0 deletions
diff --git a/drivers/char/raw.c b/drivers/char/raw.c new file mode 100644 index 000000000..5fc291c61 --- /dev/null +++ b/drivers/char/raw.c @@ -0,0 +1,369 @@ +/* + * 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/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"); |