drivers/char/raw.c

   1 /*
   2  * linux/drivers/char/raw.c
   3  *
   4  * Front-end raw character devices.  These can be bound to any block
   5  * devices to provide genuine Unix raw character device semantics.
   6  *
   7  * We reserve minor number 0 for a control interface.  ioctl()s on this
   8  * device are used to bind the other minor numbers to block devices.
   9  */
  10
  11 #include <linux/init.h>
  12 #include <linux/fs.h>
  13 #include <linux/devfs_fs_kernel.h>
  14 #include <linux/major.h>
  15 #include <linux/blkdev.h>
  16 #include <linux/module.h>
  17 #include <linux/raw.h>
  18 #include <linux/capability.h>
  19 #include <linux/uio.h>
  20 #include <linux/cdev.h>
  21 #include <linux/device.h>
  22 #include <linux/mutex.h>
  23
  24 #include <asm/uaccess.h>
  25
  26 struct raw_device_data {
  27         struct block_device *binding;
  28         int inuse;
  29 };
  30
  31 static struct class *raw_class;
  32 static struct raw_device_data raw_devices[MAX_RAW_MINORS];
  33 static DEFINE_MUTEX(raw_mutex);
  34 static struct file_operations raw_ctl_fops;          /* forward declaration */
  35
  36 /*
  37  * Open/close code for raw IO.
  38  *
  39  * We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
  40  * point at the blockdev's address_space and set the file handle to use
  41  * O_DIRECT.
  42  *
  43  * Set the device's soft blocksize to the minimum possible.  This gives the
  44  * finest possible alignment and has no adverse impact on performance.
  45  */
  46 static int raw_open(struct inode *inode, struct file *filp)
  47 {
  48         const int minor = iminor(inode);
  49         struct block_device *bdev;
  50         int err;
  51
  52         if (minor == 0) {       /* It is the control device */
  53                 filp->f_op = &raw_ctl_fops;
  54                 return 0;
  55         }
  56
  57         mutex_lock(&raw_mutex);
  58
  59         /*
  60          * All we need to do on open is check that the device is bound.
  61          */
  62         bdev = raw_devices[minor].binding;
  63         err = -ENODEV;
  64         if (!bdev)
  65                 goto out;
  66         igrab(bdev->bd_inode);
  67         err = blkdev_get(bdev, filp->f_mode, 0);
  68         if (err)
  69                 goto out;
  70         err = bd_claim(bdev, raw_open);
  71         if (err)
  72                 goto out1;
  73         err = set_blocksize(bdev, bdev_hardsect_size(bdev));
  74         if (err)
  75                 goto out2;
  76         filp->f_flags |= O_DIRECT;
  77         filp->f_mapping = bdev->bd_inode->i_mapping;
  78         if (++raw_devices[minor].inuse == 1)
  79                 filp->f_dentry->d_inode->i_mapping =
  80                         bdev->bd_inode->i_mapping;
  81         filp->private_data = bdev;
  82         mutex_unlock(&raw_mutex);
  83         return 0;
  84
  85 out2:
  86         bd_release(bdev);
  87 out1:
  88         blkdev_put(bdev);
  89 out:
  90         mutex_unlock(&raw_mutex);
  91         return err;
  92 }
  93
  94 /*
  95  * When the final fd which refers to this character-special node is closed, we
  96  * make its ->mapping point back at its own i_data.
  97  */
  98 static int raw_release(struct inode *inode, struct file *filp)
  99 {
 100         const int minor= iminor(inode);
 101         struct block_device *bdev;
 102
 103         mutex_lock(&raw_mutex);
 104         bdev = raw_devices[minor].binding;
 105         if (--raw_devices[minor].inuse == 0) {
 106                 /* Here  inode->i_mapping == bdev->bd_inode->i_mapping  */
 107                 inode->i_mapping = &inode->i_data;
 108                 inode->i_mapping->backing_dev_info = &default_backing_dev_info;
 109         }
 110         mutex_unlock(&raw_mutex);
 111
 112         bd_release(bdev);
 113         blkdev_put(bdev);
 114         return 0;
 115 }
 116
 117 /*
 118  * Forward ioctls to the underlying block device.
 119  */
 120 static int
 121 raw_ioctl(struct inode *inode, struct file *filp,
 122                   unsigned int command, unsigned long arg)
 123 {
 124         struct block_device *bdev = filp->private_data;
 125
 126         return blkdev_ioctl(bdev->bd_inode, NULL, command, arg);
 127 }
 128
 129 static void bind_device(struct raw_config_request *rq)
 130 {
 131         class_device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
 132         class_device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor),
 133                                       NULL, "raw%d", rq->raw_minor);
 134 }
 135
 136 /*
 137  * Deal with ioctls against the raw-device control interface, to bind
 138  * and unbind other raw devices.
 139  */
 140 static int raw_ctl_ioctl(struct inode *inode, struct file *filp,
 141                         unsigned int command, unsigned long arg)
 142 {
 143         struct raw_config_request rq;
 144         struct raw_device_data *rawdev;
 145         int err = 0;
 146
 147         switch (command) {
 148         case RAW_SETBIND:
 149         case RAW_GETBIND:
 150
 151                 /* First, find out which raw minor we want */
 152
 153                 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
 154                         err = -EFAULT;
 155                         goto out;
 156                 }
 157
 158                 if (rq.raw_minor < 0 || rq.raw_minor >= MAX_RAW_MINORS) {
 159                         err = -EINVAL;
 160                         goto out;
 161                 }
 162                 rawdev = &raw_devices[rq.raw_minor];
 163
 164                 if (command == RAW_SETBIND) {
 165                         dev_t dev;
 166
 167                         /*
 168                          * This is like making block devices, so demand the
 169                          * same capability
 170                          */
 171                         if (!capable(CAP_SYS_ADMIN)) {
 172                                 err = -EPERM;
 173                                 goto out;
 174                         }
 175
 176                         /*
 177                          * For now, we don't need to check that the underlying
 178                          * block device is present or not: we can do that when
 179                          * the raw device is opened.  Just check that the
 180                          * major/minor numbers make sense.
 181                          */
 182
 183                         dev = MKDEV(rq.block_major, rq.block_minor);
 184                         if ((rq.block_major == 0 && rq.block_minor != 0) ||
 185                                         MAJOR(dev) != rq.block_major ||
 186                                         MINOR(dev) != rq.block_minor) {
 187                                 err = -EINVAL;
 188                                 goto out;
 189                         }
 190
 191                         mutex_lock(&raw_mutex);
 192                         if (rawdev->inuse) {
 193                                 mutex_unlock(&raw_mutex);
 194                                 err = -EBUSY;
 195                                 goto out;
 196                         }
 197                         if (rawdev->binding) {
 198                                 bdput(rawdev->binding);
 199                                 module_put(THIS_MODULE);
 200                         }
 201                         if (rq.block_major == 0 && rq.block_minor == 0) {
 202                                 /* unbind */
 203                                 rawdev->binding = NULL;
 204                                 class_device_destroy(raw_class,
 205                                                 MKDEV(RAW_MAJOR, rq.raw_minor));
 206                         } else {
 207                                 rawdev->binding = bdget(dev);
 208                                 if (rawdev->binding == NULL)
 209                                         err = -ENOMEM;
 210                                 else {
 211                                         __module_get(THIS_MODULE);
 212                                         bind_device(&rq);
 213                                 }
 214                         }
 215                         mutex_unlock(&raw_mutex);
 216                 } else {
 217                         struct block_device *bdev;
 218
 219                         mutex_lock(&raw_mutex);
 220                         bdev = rawdev->binding;
 221                         if (bdev) {
 222                                 rq.block_major = MAJOR(bdev->bd_dev);
 223                                 rq.block_minor = MINOR(bdev->bd_dev);
 224                         } else {
 225                                 rq.block_major = rq.block_minor = 0;
 226                         }
 227                         mutex_unlock(&raw_mutex);
 228                         if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
 229                                 err = -EFAULT;
 230                                 goto out;
 231                         }
 232                 }
 233                 break;
 234         default:
 235                 err = -EINVAL;
 236                 break;
 237         }
 238 out:
 239         return err;
 240 }
 241
 242 static ssize_t raw_file_write(struct file *file, const char __user *buf,
 243                                    size_t count, loff_t *ppos)
 244 {
 245         struct iovec local_iov = {
 246                 .iov_base = (char __user *)buf,
 247                 .iov_len = count
 248         };
 249
 250         return generic_file_write_nolock(file, &local_iov, 1, ppos);
 251 }
 252
 253 static ssize_t raw_file_aio_write(struct kiocb *iocb, const char __user *buf,
 254                                         size_t count, loff_t pos)
 255 {
 256         struct iovec local_iov = {
 257                 .iov_base = (char __user *)buf,
 258                 .iov_len = count
 259         };
 260
 261         return generic_file_aio_write_nolock(iocb, &local_iov, 1, &iocb->ki_pos);
 262 }
 263
 264
 265 static struct file_operations raw_fops = {
 266         .read   =       generic_file_read,
 267         .aio_read =     generic_file_aio_read,
 268         .write  =       raw_file_write,
 269         .aio_write =    raw_file_aio_write,
 270         .open   =       raw_open,
 271         .release=       raw_release,
 272         .ioctl  =       raw_ioctl,
 273         .readv  =       generic_file_readv,
 274         .writev =       generic_file_writev,
 275         .owner  =       THIS_MODULE,
 276 };
 277
 278 static struct file_operations raw_ctl_fops = {
 279         .ioctl  =       raw_ctl_ioctl,
 280         .open   =       raw_open,
 281         .owner  =       THIS_MODULE,
 282 };
 283
 284 static struct cdev raw_cdev = {
 285         .kobj   =       {.name = "raw", },
 286         .owner  =       THIS_MODULE,
 287 };
 288
 289 static int __init raw_init(void)
 290 {
 291         int i;
 292         dev_t dev = MKDEV(RAW_MAJOR, 0);
 293
 294         if (register_chrdev_region(dev, MAX_RAW_MINORS, "raw"))
 295                 goto error;
 296
 297         cdev_init(&raw_cdev, &raw_fops);
 298         if (cdev_add(&raw_cdev, dev, MAX_RAW_MINORS)) {
 299                 kobject_put(&raw_cdev.kobj);
 300                 unregister_chrdev_region(dev, MAX_RAW_MINORS);
 301                 goto error;
 302         }
 303
 304         raw_class = class_create(THIS_MODULE, "raw");
 305         if (IS_ERR(raw_class)) {
 306                 printk(KERN_ERR "Error creating raw class.\n");
 307                 cdev_del(&raw_cdev);
 308                 unregister_chrdev_region(dev, MAX_RAW_MINORS);
 309                 goto error;
 310         }
 311         class_device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
 312
 313         devfs_mk_cdev(MKDEV(RAW_MAJOR, 0),
 314                       S_IFCHR | S_IRUGO | S_IWUGO,
 315                       "raw/rawctl");
 316         for (i = 1; i < MAX_RAW_MINORS; i++)
 317                 devfs_mk_cdev(MKDEV(RAW_MAJOR, i),
 318                               S_IFCHR | S_IRUGO | S_IWUGO,
 319                               "raw/raw%d", i);
 320         return 0;
 321
 322 error:
 323         printk(KERN_ERR "error register raw device\n");
 324         return 1;
 325 }
 326
 327 static void __exit raw_exit(void)
 328 {
 329         int i;
 330
 331         for (i = 1; i < MAX_RAW_MINORS; i++)
 332                 devfs_remove("raw/raw%d", i);
 333         devfs_remove("raw/rawctl");
 334         devfs_remove("raw");
 335         class_device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
 336         class_destroy(raw_class);
 337         cdev_del(&raw_cdev);
 338         unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
 339 }
 340
 341 module_init(raw_init);
 342 module_exit(raw_exit);
 343 MODULE_LICENSE("GPL");