1 /* 2 Added support for the AMD Geode LX RNG 3 (c) Copyright 2004-2005 Advanced Micro Devices, Inc. 4 5 derived from 6 7 Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG) 8 (c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com> 9 10 derived from 11 12 Hardware driver for the AMD 768 Random Number Generator (RNG) 13 (c) Copyright 2001 Red Hat Inc <alan@redhat.com> 14 15 derived from 16 17 Hardware driver for Intel i810 Random Number Generator (RNG) 18 Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com> 19 Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com> 20 21 Added generic RNG API 22 Copyright 2006 Michael Buesch <m@bues.ch> 23 Copyright 2005 (c) MontaVista Software, Inc. 24 25 Please read Documentation/hw_random.txt for details on use. 26 27 ---------------------------------------------------------- 28 This software may be used and distributed according to the terms 29 of the GNU General Public License, incorporated herein by reference. 30 31 */ 32 33 34 #include <linux/device.h> 35 #include <linux/hw_random.h> 36 #include <linux/module.h> 37 #include <linux/kernel.h> 38 #include <linux/fs.h> 39 #include <linux/sched.h> 40 #include <linux/miscdevice.h> 41 #include <linux/delay.h> 42 #include <linux/slab.h> 43 #include <linux/random.h> 44 #include <asm/uaccess.h> 45 46 47 #define RNG_MODULE_NAME "hw_random" 48 #define PFX RNG_MODULE_NAME ": " 49 #define RNG_MISCDEV_MINOR 183 /* official */ 50 51 52 static struct hwrng *current_rng; 53 static LIST_HEAD(rng_list); 54 static DEFINE_MUTEX(rng_mutex); 55 static int data_avail; 56 static u8 *rng_buffer; 57 58 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, 59 int wait); 60 61 static size_t rng_buffer_size(void) 62 { 63 return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES; 64 } 65 66 static void add_early_randomness(struct hwrng *rng) 67 { 68 unsigned char bytes[16]; 69 int bytes_read; 70 71 /* 72 * Currently only virtio-rng cannot return data during device 73 * probe, and that's handled in virtio-rng.c itself. If there 74 * are more such devices, this call to rng_get_data can be 75 * made conditional here instead of doing it per-device. 76 */ 77 bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1); 78 if (bytes_read > 0) 79 add_device_randomness(bytes, bytes_read); 80 } 81 82 static inline int hwrng_init(struct hwrng *rng) 83 { 84 if (rng->init) { 85 int ret; 86 87 ret = rng->init(rng); 88 if (ret) 89 return ret; 90 } 91 add_early_randomness(rng); 92 return 0; 93 } 94 95 static inline void hwrng_cleanup(struct hwrng *rng) 96 { 97 if (rng && rng->cleanup) 98 rng->cleanup(rng); 99 } 100 101 static int rng_dev_open(struct inode *inode, struct file *filp) 102 { 103 /* enforce read-only access to this chrdev */ 104 if ((filp->f_mode & FMODE_READ) == 0) 105 return -EINVAL; 106 if (filp->f_mode & FMODE_WRITE) 107 return -EINVAL; 108 return 0; 109 } 110 111 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, 112 int wait) { 113 int present; 114 115 if (rng->read) 116 return rng->read(rng, (void *)buffer, size, wait); 117 118 if (rng->data_present) 119 present = rng->data_present(rng, wait); 120 else 121 present = 1; 122 123 if (present) 124 return rng->data_read(rng, (u32 *)buffer); 125 126 return 0; 127 } 128 129 static ssize_t rng_dev_read(struct file *filp, char __user *buf, 130 size_t size, loff_t *offp) 131 { 132 ssize_t ret = 0; 133 int err = 0; 134 int bytes_read, len; 135 136 while (size) { 137 if (mutex_lock_interruptible(&rng_mutex)) { 138 err = -ERESTARTSYS; 139 goto out; 140 } 141 142 if (!current_rng) { 143 err = -ENODEV; 144 goto out_unlock; 145 } 146 147 if (!data_avail) { 148 bytes_read = rng_get_data(current_rng, rng_buffer, 149 rng_buffer_size(), 150 !(filp->f_flags & O_NONBLOCK)); 151 if (bytes_read < 0) { 152 err = bytes_read; 153 goto out_unlock; 154 } 155 data_avail = bytes_read; 156 } 157 158 if (!data_avail) { 159 if (filp->f_flags & O_NONBLOCK) { 160 err = -EAGAIN; 161 goto out_unlock; 162 } 163 } else { 164 len = data_avail; 165 if (len > size) 166 len = size; 167 168 data_avail -= len; 169 170 if (copy_to_user(buf + ret, rng_buffer + data_avail, 171 len)) { 172 err = -EFAULT; 173 goto out_unlock; 174 } 175 176 size -= len; 177 ret += len; 178 } 179 180 mutex_unlock(&rng_mutex); 181 182 if (need_resched()) 183 schedule_timeout_interruptible(1); 184 185 if (signal_pending(current)) { 186 err = -ERESTARTSYS; 187 goto out; 188 } 189 } 190 out: 191 return ret ? : err; 192 out_unlock: 193 mutex_unlock(&rng_mutex); 194 goto out; 195 } 196 197 198 static const struct file_operations rng_chrdev_ops = { 199 .owner = THIS_MODULE, 200 .open = rng_dev_open, 201 .read = rng_dev_read, 202 .llseek = noop_llseek, 203 }; 204 205 static struct miscdevice rng_miscdev = { 206 .minor = RNG_MISCDEV_MINOR, 207 .name = RNG_MODULE_NAME, 208 .nodename = "hwrng", 209 .fops = &rng_chrdev_ops, 210 }; 211 212 213 static ssize_t hwrng_attr_current_store(struct device *dev, 214 struct device_attribute *attr, 215 const char *buf, size_t len) 216 { 217 int err; 218 struct hwrng *rng; 219 220 err = mutex_lock_interruptible(&rng_mutex); 221 if (err) 222 return -ERESTARTSYS; 223 err = -ENODEV; 224 list_for_each_entry(rng, &rng_list, list) { 225 if (strcmp(rng->name, buf) == 0) { 226 if (rng == current_rng) { 227 err = 0; 228 break; 229 } 230 err = hwrng_init(rng); 231 if (err) 232 break; 233 hwrng_cleanup(current_rng); 234 current_rng = rng; 235 err = 0; 236 break; 237 } 238 } 239 mutex_unlock(&rng_mutex); 240 241 return err ? : len; 242 } 243 244 static ssize_t hwrng_attr_current_show(struct device *dev, 245 struct device_attribute *attr, 246 char *buf) 247 { 248 int err; 249 ssize_t ret; 250 const char *name = "none"; 251 252 err = mutex_lock_interruptible(&rng_mutex); 253 if (err) 254 return -ERESTARTSYS; 255 if (current_rng) 256 name = current_rng->name; 257 ret = snprintf(buf, PAGE_SIZE, "%s\n", name); 258 mutex_unlock(&rng_mutex); 259 260 return ret; 261 } 262 263 static ssize_t hwrng_attr_available_show(struct device *dev, 264 struct device_attribute *attr, 265 char *buf) 266 { 267 int err; 268 ssize_t ret = 0; 269 struct hwrng *rng; 270 271 err = mutex_lock_interruptible(&rng_mutex); 272 if (err) 273 return -ERESTARTSYS; 274 buf[0] = '\0'; 275 list_for_each_entry(rng, &rng_list, list) { 276 strncat(buf, rng->name, PAGE_SIZE - ret - 1); 277 ret += strlen(rng->name); 278 strncat(buf, " ", PAGE_SIZE - ret - 1); 279 ret++; 280 } 281 strncat(buf, "\n", PAGE_SIZE - ret - 1); 282 ret++; 283 mutex_unlock(&rng_mutex); 284 285 return ret; 286 } 287 288 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR, 289 hwrng_attr_current_show, 290 hwrng_attr_current_store); 291 static DEVICE_ATTR(rng_available, S_IRUGO, 292 hwrng_attr_available_show, 293 NULL); 294 295 296 static void unregister_miscdev(void) 297 { 298 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available); 299 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 300 misc_deregister(&rng_miscdev); 301 } 302 303 static int register_miscdev(void) 304 { 305 int err; 306 307 err = misc_register(&rng_miscdev); 308 if (err) 309 goto out; 310 err = device_create_file(rng_miscdev.this_device, 311 &dev_attr_rng_current); 312 if (err) 313 goto err_misc_dereg; 314 err = device_create_file(rng_miscdev.this_device, 315 &dev_attr_rng_available); 316 if (err) 317 goto err_remove_current; 318 out: 319 return err; 320 321 err_remove_current: 322 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 323 err_misc_dereg: 324 misc_deregister(&rng_miscdev); 325 goto out; 326 } 327 328 int hwrng_register(struct hwrng *rng) 329 { 330 int err = -EINVAL; 331 struct hwrng *old_rng, *tmp; 332 333 if (rng->name == NULL || 334 (rng->data_read == NULL && rng->read == NULL)) 335 goto out; 336 337 mutex_lock(&rng_mutex); 338 339 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */ 340 err = -ENOMEM; 341 if (!rng_buffer) { 342 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL); 343 if (!rng_buffer) 344 goto out_unlock; 345 } 346 347 /* Must not register two RNGs with the same name. */ 348 err = -EEXIST; 349 list_for_each_entry(tmp, &rng_list, list) { 350 if (strcmp(tmp->name, rng->name) == 0) 351 goto out_unlock; 352 } 353 354 old_rng = current_rng; 355 if (!old_rng) { 356 err = hwrng_init(rng); 357 if (err) 358 goto out_unlock; 359 current_rng = rng; 360 } 361 err = 0; 362 if (!old_rng) { 363 err = register_miscdev(); 364 if (err) { 365 hwrng_cleanup(rng); 366 current_rng = NULL; 367 goto out_unlock; 368 } 369 } 370 INIT_LIST_HEAD(&rng->list); 371 list_add_tail(&rng->list, &rng_list); 372 373 if (old_rng && !rng->init) { 374 /* 375 * Use a new device's input to add some randomness to 376 * the system. If this rng device isn't going to be 377 * used right away, its init function hasn't been 378 * called yet; so only use the randomness from devices 379 * that don't need an init callback. 380 */ 381 add_early_randomness(rng); 382 } 383 384 out_unlock: 385 mutex_unlock(&rng_mutex); 386 out: 387 return err; 388 } 389 EXPORT_SYMBOL_GPL(hwrng_register); 390 391 void hwrng_unregister(struct hwrng *rng) 392 { 393 int err; 394 395 mutex_lock(&rng_mutex); 396 397 list_del(&rng->list); 398 if (current_rng == rng) { 399 hwrng_cleanup(rng); 400 if (list_empty(&rng_list)) { 401 current_rng = NULL; 402 } else { 403 current_rng = list_entry(rng_list.prev, struct hwrng, list); 404 err = hwrng_init(current_rng); 405 if (err) 406 current_rng = NULL; 407 } 408 } 409 if (list_empty(&rng_list)) 410 unregister_miscdev(); 411 412 mutex_unlock(&rng_mutex); 413 } 414 EXPORT_SYMBOL_GPL(hwrng_unregister); 415 416 static void __exit hwrng_exit(void) 417 { 418 mutex_lock(&rng_mutex); 419 BUG_ON(current_rng); 420 kfree(rng_buffer); 421 mutex_unlock(&rng_mutex); 422 } 423 424 module_exit(hwrng_exit); 425 426 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver"); 427 MODULE_LICENSE("GPL"); 428