| 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 | filp->f_path.dentry->d_inode->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 | inode->i_mapping->backing_dev_info = &default_backing_dev_info; |
| 111 | } |
| 112 | mutex_unlock(&raw_mutex); |
| 113 | |
| 114 | blkdev_put(bdev, filp->f_mode | FMODE_EXCL); |
| 115 | return 0; |
| 116 | } |
| 117 | |
| 118 | /* |
| 119 | * Forward ioctls to the underlying block device. |
| 120 | */ |
| 121 | static long |
| 122 | raw_ioctl(struct file *filp, unsigned int command, unsigned long arg) |
| 123 | { |
| 124 | struct block_device *bdev = filp->private_data; |
| 125 | return blkdev_ioctl(bdev, 0, command, arg); |
| 126 | } |
| 127 | |
| 128 | static int bind_set(int number, u64 major, u64 minor) |
| 129 | { |
| 130 | dev_t dev = MKDEV(major, minor); |
| 131 | struct raw_device_data *rawdev; |
| 132 | int err = 0; |
| 133 | |
| 134 | if (number <= 0 || number >= max_raw_minors) |
| 135 | return -EINVAL; |
| 136 | |
| 137 | if (MAJOR(dev) != major || MINOR(dev) != minor) |
| 138 | return -EINVAL; |
| 139 | |
| 140 | rawdev = &raw_devices[number]; |
| 141 | |
| 142 | /* |
| 143 | * This is like making block devices, so demand the |
| 144 | * same capability |
| 145 | */ |
| 146 | if (!capable(CAP_SYS_ADMIN)) |
| 147 | return -EPERM; |
| 148 | |
| 149 | /* |
| 150 | * For now, we don't need to check that the underlying |
| 151 | * block device is present or not: we can do that when |
| 152 | * the raw device is opened. Just check that the |
| 153 | * major/minor numbers make sense. |
| 154 | */ |
| 155 | |
| 156 | if (MAJOR(dev) == 0 && dev != 0) |
| 157 | return -EINVAL; |
| 158 | |
| 159 | mutex_lock(&raw_mutex); |
| 160 | if (rawdev->inuse) { |
| 161 | mutex_unlock(&raw_mutex); |
| 162 | return -EBUSY; |
| 163 | } |
| 164 | if (rawdev->binding) { |
| 165 | bdput(rawdev->binding); |
| 166 | module_put(THIS_MODULE); |
| 167 | } |
| 168 | if (!dev) { |
| 169 | /* unbind */ |
| 170 | rawdev->binding = NULL; |
| 171 | device_destroy(raw_class, MKDEV(RAW_MAJOR, number)); |
| 172 | } else { |
| 173 | rawdev->binding = bdget(dev); |
| 174 | if (rawdev->binding == NULL) { |
| 175 | err = -ENOMEM; |
| 176 | } else { |
| 177 | dev_t raw = MKDEV(RAW_MAJOR, number); |
| 178 | __module_get(THIS_MODULE); |
| 179 | device_destroy(raw_class, raw); |
| 180 | device_create(raw_class, NULL, raw, NULL, |
| 181 | "raw%d", number); |
| 182 | } |
| 183 | } |
| 184 | mutex_unlock(&raw_mutex); |
| 185 | return err; |
| 186 | } |
| 187 | |
| 188 | static int bind_get(int number, dev_t *dev) |
| 189 | { |
| 190 | struct raw_device_data *rawdev; |
| 191 | struct block_device *bdev; |
| 192 | |
| 193 | if (number <= 0 || number >= MAX_RAW_MINORS) |
| 194 | return -EINVAL; |
| 195 | |
| 196 | rawdev = &raw_devices[number]; |
| 197 | |
| 198 | mutex_lock(&raw_mutex); |
| 199 | bdev = rawdev->binding; |
| 200 | *dev = bdev ? bdev->bd_dev : 0; |
| 201 | mutex_unlock(&raw_mutex); |
| 202 | return 0; |
| 203 | } |
| 204 | |
| 205 | /* |
| 206 | * Deal with ioctls against the raw-device control interface, to bind |
| 207 | * and unbind other raw devices. |
| 208 | */ |
| 209 | static long raw_ctl_ioctl(struct file *filp, unsigned int command, |
| 210 | unsigned long arg) |
| 211 | { |
| 212 | struct raw_config_request rq; |
| 213 | dev_t dev; |
| 214 | int err; |
| 215 | |
| 216 | switch (command) { |
| 217 | case RAW_SETBIND: |
| 218 | if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) |
| 219 | return -EFAULT; |
| 220 | |
| 221 | return bind_set(rq.raw_minor, rq.block_major, rq.block_minor); |
| 222 | |
| 223 | case RAW_GETBIND: |
| 224 | if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) |
| 225 | return -EFAULT; |
| 226 | |
| 227 | err = bind_get(rq.raw_minor, &dev); |
| 228 | if (err) |
| 229 | return err; |
| 230 | |
| 231 | rq.block_major = MAJOR(dev); |
| 232 | rq.block_minor = MINOR(dev); |
| 233 | |
| 234 | if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) |
| 235 | return -EFAULT; |
| 236 | |
| 237 | return 0; |
| 238 | } |
| 239 | |
| 240 | return -EINVAL; |
| 241 | } |
| 242 | |
| 243 | #ifdef CONFIG_COMPAT |
| 244 | struct raw32_config_request { |
| 245 | compat_int_t raw_minor; |
| 246 | compat_u64 block_major; |
| 247 | compat_u64 block_minor; |
| 248 | }; |
| 249 | |
| 250 | static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd, |
| 251 | unsigned long arg) |
| 252 | { |
| 253 | struct raw32_config_request __user *user_req = compat_ptr(arg); |
| 254 | struct raw32_config_request rq; |
| 255 | dev_t dev; |
| 256 | int err = 0; |
| 257 | |
| 258 | switch (cmd) { |
| 259 | case RAW_SETBIND: |
| 260 | if (copy_from_user(&rq, user_req, sizeof(rq))) |
| 261 | return -EFAULT; |
| 262 | |
| 263 | return bind_set(rq.raw_minor, rq.block_major, rq.block_minor); |
| 264 | |
| 265 | case RAW_GETBIND: |
| 266 | if (copy_from_user(&rq, user_req, sizeof(rq))) |
| 267 | return -EFAULT; |
| 268 | |
| 269 | err = bind_get(rq.raw_minor, &dev); |
| 270 | if (err) |
| 271 | return err; |
| 272 | |
| 273 | rq.block_major = MAJOR(dev); |
| 274 | rq.block_minor = MINOR(dev); |
| 275 | |
| 276 | if (copy_to_user(user_req, &rq, sizeof(rq))) |
| 277 | return -EFAULT; |
| 278 | |
| 279 | return 0; |
| 280 | } |
| 281 | |
| 282 | return -EINVAL; |
| 283 | } |
| 284 | #endif |
| 285 | |
| 286 | static const struct file_operations raw_fops = { |
| 287 | .read = do_sync_read, |
| 288 | .aio_read = generic_file_aio_read, |
| 289 | .write = do_sync_write, |
| 290 | .aio_write = blkdev_aio_write, |
| 291 | .fsync = blkdev_fsync, |
| 292 | .open = raw_open, |
| 293 | .release = raw_release, |
| 294 | .unlocked_ioctl = raw_ioctl, |
| 295 | .llseek = default_llseek, |
| 296 | .owner = THIS_MODULE, |
| 297 | }; |
| 298 | |
| 299 | static const struct file_operations raw_ctl_fops = { |
| 300 | .unlocked_ioctl = raw_ctl_ioctl, |
| 301 | #ifdef CONFIG_COMPAT |
| 302 | .compat_ioctl = raw_ctl_compat_ioctl, |
| 303 | #endif |
| 304 | .open = raw_open, |
| 305 | .owner = THIS_MODULE, |
| 306 | .llseek = noop_llseek, |
| 307 | }; |
| 308 | |
| 309 | static struct cdev raw_cdev; |
| 310 | |
| 311 | static char *raw_devnode(struct device *dev, umode_t *mode) |
| 312 | { |
| 313 | return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev)); |
| 314 | } |
| 315 | |
| 316 | static int __init raw_init(void) |
| 317 | { |
| 318 | dev_t dev = MKDEV(RAW_MAJOR, 0); |
| 319 | int ret; |
| 320 | |
| 321 | if (max_raw_minors < 1 || max_raw_minors > 65536) { |
| 322 | printk(KERN_WARNING "raw: invalid max_raw_minors (must be" |
| 323 | " between 1 and 65536), using %d\n", MAX_RAW_MINORS); |
| 324 | max_raw_minors = MAX_RAW_MINORS; |
| 325 | } |
| 326 | |
| 327 | raw_devices = vzalloc(sizeof(struct raw_device_data) * max_raw_minors); |
| 328 | if (!raw_devices) { |
| 329 | printk(KERN_ERR "Not enough memory for raw device structures\n"); |
| 330 | ret = -ENOMEM; |
| 331 | goto error; |
| 332 | } |
| 333 | |
| 334 | ret = register_chrdev_region(dev, max_raw_minors, "raw"); |
| 335 | if (ret) |
| 336 | goto error; |
| 337 | |
| 338 | cdev_init(&raw_cdev, &raw_fops); |
| 339 | ret = cdev_add(&raw_cdev, dev, max_raw_minors); |
| 340 | if (ret) { |
| 341 | goto error_region; |
| 342 | } |
| 343 | |
| 344 | raw_class = class_create(THIS_MODULE, "raw"); |
| 345 | if (IS_ERR(raw_class)) { |
| 346 | printk(KERN_ERR "Error creating raw class.\n"); |
| 347 | cdev_del(&raw_cdev); |
| 348 | ret = PTR_ERR(raw_class); |
| 349 | goto error_region; |
| 350 | } |
| 351 | raw_class->devnode = raw_devnode; |
| 352 | device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl"); |
| 353 | |
| 354 | return 0; |
| 355 | |
| 356 | error_region: |
| 357 | unregister_chrdev_region(dev, max_raw_minors); |
| 358 | error: |
| 359 | vfree(raw_devices); |
| 360 | return ret; |
| 361 | } |
| 362 | |
| 363 | static void __exit raw_exit(void) |
| 364 | { |
| 365 | device_destroy(raw_class, MKDEV(RAW_MAJOR, 0)); |
| 366 | class_destroy(raw_class); |
| 367 | cdev_del(&raw_cdev); |
| 368 | unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), max_raw_minors); |
| 369 | } |
| 370 | |
| 371 | module_init(raw_init); |
| 372 | module_exit(raw_exit); |
| 373 | MODULE_LICENSE("GPL"); |