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 28struct raw_device_data { 29 struct block_device *binding; 30 int inuse; 31}; 32 33static struct class *raw_class; 34static struct raw_device_data *raw_devices; 35static DEFINE_MUTEX(raw_mutex); 36static const struct file_operations raw_ctl_fops; /* forward declaration */ 37 38static int max_raw_minors = MAX_RAW_MINORS; 39 40module_param(max_raw_minors, int, 0); 41MODULE_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 */ 53static 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 89out1: 90 blkdev_put(bdev, filp->f_mode | FMODE_EXCL); 91out: 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 */ 100static 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 */ 119static long 120raw_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 126static 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 186static 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 */ 207static 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 242struct raw32_config_request { 243 compat_int_t raw_minor; 244 compat_u64 block_major; 245 compat_u64 block_minor; 246}; 247 248static 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 284static const struct file_operations raw_fops = { 285 .read_iter = blkdev_read_iter, 286 .write_iter = blkdev_write_iter, 287 .fsync = blkdev_fsync, 288 .open = raw_open, 289 .release = raw_release, 290 .unlocked_ioctl = raw_ioctl, 291 .llseek = default_llseek, 292 .owner = THIS_MODULE, 293}; 294 295static const struct file_operations raw_ctl_fops = { 296 .unlocked_ioctl = raw_ctl_ioctl, 297#ifdef CONFIG_COMPAT 298 .compat_ioctl = raw_ctl_compat_ioctl, 299#endif 300 .open = raw_open, 301 .owner = THIS_MODULE, 302 .llseek = noop_llseek, 303}; 304 305static struct cdev raw_cdev; 306 307static char *raw_devnode(struct device *dev, umode_t *mode) 308{ 309 return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev)); 310} 311 312static int __init raw_init(void) 313{ 314 dev_t dev = MKDEV(RAW_MAJOR, 0); 315 int ret; 316 317 if (max_raw_minors < 1 || max_raw_minors > 65536) { 318 printk(KERN_WARNING "raw: invalid max_raw_minors (must be" 319 " between 1 and 65536), using %d\n", MAX_RAW_MINORS); 320 max_raw_minors = MAX_RAW_MINORS; 321 } 322 323 raw_devices = vzalloc(sizeof(struct raw_device_data) * max_raw_minors); 324 if (!raw_devices) { 325 printk(KERN_ERR "Not enough memory for raw device structures\n"); 326 ret = -ENOMEM; 327 goto error; 328 } 329 330 ret = register_chrdev_region(dev, max_raw_minors, "raw"); 331 if (ret) 332 goto error; 333 334 cdev_init(&raw_cdev, &raw_fops); 335 ret = cdev_add(&raw_cdev, dev, max_raw_minors); 336 if (ret) { 337 goto error_region; 338 } 339 340 raw_class = class_create(THIS_MODULE, "raw"); 341 if (IS_ERR(raw_class)) { 342 printk(KERN_ERR "Error creating raw class.\n"); 343 cdev_del(&raw_cdev); 344 ret = PTR_ERR(raw_class); 345 goto error_region; 346 } 347 raw_class->devnode = raw_devnode; 348 device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl"); 349 350 return 0; 351 352error_region: 353 unregister_chrdev_region(dev, max_raw_minors); 354error: 355 vfree(raw_devices); 356 return ret; 357} 358 359static void __exit raw_exit(void) 360{ 361 device_destroy(raw_class, MKDEV(RAW_MAJOR, 0)); 362 class_destroy(raw_class); 363 cdev_del(&raw_cdev); 364 unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), max_raw_minors); 365} 366 367module_init(raw_init); 368module_exit(raw_exit); 369MODULE_LICENSE("GPL"); 370