/drivers/char/raw.c
C | 374 lines | 269 code | 60 blank | 45 comment | 45 complexity | 9552c3df8df8eb2d95bcfeab493389af MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
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 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 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 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 */ 121static long 122raw_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 128static 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 188static 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 */ 209static 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 244struct raw32_config_request { 245 compat_int_t raw_minor; 246 compat_u64 block_major; 247 compat_u64 block_minor; 248}; 249 250static 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 286static 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 299static 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 309static struct cdev raw_cdev; 310 311static char *raw_devnode(struct device *dev, mode_t *mode) 312{ 313 return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev)); 314} 315 316static 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 = vmalloc(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 memset(raw_devices, 0, sizeof(struct raw_device_data) * max_raw_minors); 334 335 ret = register_chrdev_region(dev, max_raw_minors, "raw"); 336 if (ret) 337 goto error; 338 339 cdev_init(&raw_cdev, &raw_fops); 340 ret = cdev_add(&raw_cdev, dev, max_raw_minors); 341 if (ret) { 342 goto error_region; 343 } 344 345 raw_class = class_create(THIS_MODULE, "raw"); 346 if (IS_ERR(raw_class)) { 347 printk(KERN_ERR "Error creating raw class.\n"); 348 cdev_del(&raw_cdev); 349 ret = PTR_ERR(raw_class); 350 goto error_region; 351 } 352 raw_class->devnode = raw_devnode; 353 device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl"); 354 355 return 0; 356 357error_region: 358 unregister_chrdev_region(dev, max_raw_minors); 359error: 360 vfree(raw_devices); 361 return ret; 362} 363 364static void __exit raw_exit(void) 365{ 366 device_destroy(raw_class, MKDEV(RAW_MAJOR, 0)); 367 class_destroy(raw_class); 368 cdev_del(&raw_cdev); 369 unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), max_raw_minors); 370} 371 372module_init(raw_init); 373module_exit(raw_exit); 374MODULE_LICENSE("GPL");