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/major.h>
  14 #include <linux/blkdev.h>
  15 #include <linux/module.h>
  16 #include <linux/raw.h>
  17 #include <linux/capability.h>
  18 #include <linux/uio.h>
  19 #include <linux/cdev.h>
  20 #include <linux/device.h>
  21 #include <linux/mutex.h>
  22 #include <linux/gfp.h>
  23 #include <linux/compat.h>
  24 #include <linux/vmalloc.h>
  25
  26 #include <asm/uaccess.h>
  27
  28 struct raw_device_data {
  29         struct block_device *binding;
  30         int inuse;
  31 };
  32
  33 static struct class *raw_class;
  34 static struct raw_device_data *raw_devices;
  35 static DEFINE_MUTEX(raw_mutex);
  36 static const struct file_operations raw_ctl_fops; /* forward declaration */
  37
  38 static int max_raw_minors = MAX_RAW_MINORS;
  39
  40 module_param(max_raw_minors, int, 0);
  41 MODULE_PARM_DESC(max_raw_minors, "Maximum number of raw devices (1-65536)");
  42
  43 /*
  44  * Open/close code for raw IO.
  45  *
  46  * We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
  47  * point at the blockdev's address_space and set the file handle to use
  48  * O_DIRECT.
  49  *
  50  * Set the device's soft blocksize to the minimum possible.  This gives the
  51  * finest possible alignment and has no adverse impact on performance.
  52  */
  53 static int raw_open(struct inode *inode, struct file *filp)
  54 {
  55         const int minor = iminor(inode);
  56         struct block_device *bdev;
  57         int err;
  58
  59         if (minor == 0) {       /* It is the control device */
  60                 filp->f_op = &raw_ctl_fops;
  61                 return 0;
  62         }
  63
  64         mutex_lock(&raw_mutex);
  65
  66         /*
  67          * All we need to do on open is check that the device is bound.
  68          */
  69         bdev = raw_devices[minor].binding;
  70         err = -ENODEV;
  71         if (!bdev)
  72                 goto out;
  73         igrab(bdev->bd_inode);
  74         err = blkdev_get(bdev, filp->f_mode | FMODE_EXCL, raw_open);
  75         if (err)
  76                 goto out;
  77         err = set_blocksize(bdev, bdev_logical_block_size(bdev));
  78         if (err)
  79                 goto out1;
  80         filp->f_flags |= O_DIRECT;
  81         filp->f_mapping = bdev->bd_inode->i_mapping;
  82         if (++raw_devices[minor].inuse == 1)
  83                 file_inode(filp)->i_mapping =
  84                         bdev->bd_inode->i_mapping;
  85         filp->private_data = bdev;
  86         mutex_unlock(&raw_mutex);
  87         return 0;
  88
  89 out1:
  90         blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
  91 out:
  92         mutex_unlock(&raw_mutex);
  93         return err;
  94 }
  95
  96 /*
  97  * When the final fd which refers to this character-special node is closed, we
  98  * make its ->mapping point back at its own i_data.
  99  */
 100 static int raw_release(struct inode *inode, struct file *filp)
 101 {
 102         const int minor= iminor(inode);
 103         struct block_device *bdev;
 104
 105         mutex_lock(&raw_mutex);
 106         bdev = raw_devices[minor].binding;
 107         if (--raw_devices[minor].inuse == 0)
 108                 /* Here  inode->i_mapping == bdev->bd_inode->i_mapping  */
 109                 inode->i_mapping = &inode->i_data;
 110         mutex_unlock(&raw_mutex);
 111
 112         blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
 113         return 0;
 114 }
 115
 116 /*
 117  * Forward ioctls to the underlying block device.
 118  */
 119 static long
 120 raw_ioctl(struct file *filp, unsigned int command, unsigned long arg)
 121 {
 122         struct block_device *bdev = filp->private_data;
 123         return blkdev_ioctl(bdev, 0, command, arg);
 124 }
 125
 126 static int bind_set(int number, u64 major, u64 minor)
 127 {
 128         dev_t dev = MKDEV(major, minor);
 129         struct raw_device_data *rawdev;
 130         int err = 0;
 131
 132         if (number <= 0 || number >= max_raw_minors)
 133                 return -EINVAL;
 134
 135         if (MAJOR(dev) != major || MINOR(dev) != minor)
 136                 return -EINVAL;
 137
 138         rawdev = &raw_devices[number];
 139
 140         /*
 141          * This is like making block devices, so demand the
 142          * same capability
 143          */
 144         if (!capable(CAP_SYS_ADMIN))
 145                 return -EPERM;
 146
 147         /*
 148          * For now, we don't need to check that the underlying
 149          * block device is present or not: we can do that when
 150          * the raw device is opened.  Just check that the
 151          * major/minor numbers make sense.
 152          */
 153
 154         if (MAJOR(dev) == 0 && dev != 0)
 155                 return -EINVAL;
 156
 157         mutex_lock(&raw_mutex);
 158         if (rawdev->inuse) {
 159                 mutex_unlock(&raw_mutex);
 160                 return -EBUSY;
 161         }
 162         if (rawdev->binding) {
 163                 bdput(rawdev->binding);
 164                 module_put(THIS_MODULE);
 165         }
 166         if (!dev) {
 167                 /* unbind */
 168                 rawdev->binding = NULL;
 169                 device_destroy(raw_class, MKDEV(RAW_MAJOR, number));
 170         } else {
 171                 rawdev->binding = bdget(dev);
 172                 if (rawdev->binding == NULL) {
 173                         err = -ENOMEM;
 174                 } else {
 175                         dev_t raw = MKDEV(RAW_MAJOR, number);
 176                         __module_get(THIS_MODULE);
 177                         device_destroy(raw_class, raw);
 178                         device_create(raw_class, NULL, raw, NULL,
 179                                       "raw%d", number);
 180                 }
 181         }
 182         mutex_unlock(&raw_mutex);
 183         return err;
 184 }
 185
 186 static int bind_get(int number, dev_t *dev)
 187 {
 188         struct raw_device_data *rawdev;
 189         struct block_device *bdev;
 190
 191         if (number <= 0 || number >= max_raw_minors)
 192                 return -EINVAL;
 193
 194         rawdev = &raw_devices[number];
 195
 196         mutex_lock(&raw_mutex);
 197         bdev = rawdev->binding;
 198         *dev = bdev ? bdev->bd_dev : 0;
 199         mutex_unlock(&raw_mutex);
 200         return 0;
 201 }
 202
 203 /*
 204  * Deal with ioctls against the raw-device control interface, to bind
 205  * and unbind other raw devices.
 206  */
 207 static long raw_ctl_ioctl(struct file *filp, unsigned int command,
 208                           unsigned long arg)
 209 {
 210         struct raw_config_request rq;
 211         dev_t dev;
 212         int err;
 213
 214         switch (command) {
 215         case RAW_SETBIND:
 216                 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
 217                         return -EFAULT;
 218
 219                 return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
 220
 221         case RAW_GETBIND:
 222                 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
 223                         return -EFAULT;
 224
 225                 err = bind_get(rq.raw_minor, &dev);
 226                 if (err)
 227                         return err;
 228
 229                 rq.block_major = MAJOR(dev);
 230                 rq.block_minor = MINOR(dev);
 231
 232                 if (copy_to_user((void __user *)arg, &rq, sizeof(rq)))
 233                         return -EFAULT;
 234
 235                 return 0;
 236         }
 237
 238         return -EINVAL;
 239 }
 240
 241 #ifdef CONFIG_COMPAT
 242 struct raw32_config_request {
 243         compat_int_t    raw_minor;
 244         compat_u64      block_major;
 245         compat_u64      block_minor;
 246 };
 247
 248 static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
 249                                 unsigned long arg)
 250 {
 251         struct raw32_config_request __user *user_req = compat_ptr(arg);
 252         struct raw32_config_request rq;
 253         dev_t dev;
 254         int err = 0;
 255
 256         switch (cmd) {
 257         case RAW_SETBIND:
 258                 if (copy_from_user(&rq, user_req, sizeof(rq)))
 259                         return -EFAULT;
 260
 261                 return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
 262
 263         case RAW_GETBIND:
 264                 if (copy_from_user(&rq, user_req, sizeof(rq)))
 265                         return -EFAULT;
 266
 267                 err = bind_get(rq.raw_minor, &dev);
 268                 if (err)
 269                         return err;
 270
 271                 rq.block_major = MAJOR(dev);
 272                 rq.block_minor = MINOR(dev);
 273
 274                 if (copy_to_user(user_req, &rq, sizeof(rq)))
 275                         return -EFAULT;
 276
 277                 return 0;
 278         }
 279
 280         return -EINVAL;
 281 }
 282 #endif
 283
 284 static const struct file_operations raw_fops = {
 285         .read           = new_sync_read,
 286         .read_iter      = blkdev_read_iter,
 287         .write          = new_sync_write,
 288         .write_iter     = blkdev_write_iter,
 289         .fsync          = blkdev_fsync,
 290         .open           = raw_open,
 291         .release        = raw_release,
 292         .unlocked_ioctl = raw_ioctl,
 293         .llseek         = default_llseek,
 294         .owner          = THIS_MODULE,
 295 };
 296
 297 static const struct file_operations raw_ctl_fops = {
 298         .unlocked_ioctl = raw_ctl_ioctl,
 299 #ifdef CONFIG_COMPAT
 300         .compat_ioctl   = raw_ctl_compat_ioctl,
 301 #endif
 302         .open           = raw_open,
 303         .owner          = THIS_MODULE,
 304         .llseek         = noop_llseek,
 305 };
 306
 307 static struct cdev raw_cdev;
 308
 309 static char *raw_devnode(struct device *dev, umode_t *mode)
 310 {
 311         return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev));
 312 }
 313
 314 static int __init raw_init(void)
 315 {
 316         dev_t dev = MKDEV(RAW_MAJOR, 0);
 317         int ret;
 318
 319         if (max_raw_minors < 1 || max_raw_minors > 65536) {
 320                 printk(KERN_WARNING "raw: invalid max_raw_minors (must be"
 321                         " between 1 and 65536), using %d\n", MAX_RAW_MINORS);
 322                 max_raw_minors = MAX_RAW_MINORS;
 323         }
 324
 325         raw_devices = vzalloc(sizeof(struct raw_device_data) * max_raw_minors);
 326         if (!raw_devices) {
 327                 printk(KERN_ERR "Not enough memory for raw device structures\n");
 328                 ret = -ENOMEM;
 329                 goto error;
 330         }
 331
 332         ret = register_chrdev_region(dev, max_raw_minors, "raw");
 333         if (ret)
 334                 goto error;
 335
 336         cdev_init(&raw_cdev, &raw_fops);
 337         ret = cdev_add(&raw_cdev, dev, max_raw_minors);
 338         if (ret) {
 339                 goto error_region;
 340         }
 341
 342         raw_class = class_create(THIS_MODULE, "raw");
 343         if (IS_ERR(raw_class)) {
 344                 printk(KERN_ERR "Error creating raw class.\n");
 345                 cdev_del(&raw_cdev);
 346                 ret = PTR_ERR(raw_class);
 347                 goto error_region;
 348         }
 349         raw_class->devnode = raw_devnode;
 350         device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
 351
 352         return 0;
 353
 354 error_region:
 355         unregister_chrdev_region(dev, max_raw_minors);
 356 error:
 357         vfree(raw_devices);
 358         return ret;
 359 }
 360
 361 static void __exit raw_exit(void)
 362 {
 363         device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
 364         class_destroy(raw_class);
 365         cdev_del(&raw_cdev);
 366         unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), max_raw_minors);
 367 }
 368
 369 module_init(raw_init);
 370 module_exit(raw_exit);
 371 MODULE_LICENSE("GPL");