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 <mbuesch@freenet.de> 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/init.h> 41 #include <linux/miscdevice.h> 42 #include <linux/delay.h> 43 #include <asm/uaccess.h> 44 45 46 #define RNG_MODULE_NAME "hw_random" 47 #define PFX RNG_MODULE_NAME ": " 48 #define RNG_MISCDEV_MINOR 183 /* official */ 49 50 51 static struct hwrng *current_rng; 52 static LIST_HEAD(rng_list); 53 static DEFINE_MUTEX(rng_mutex); 54 static int data_avail; 55 static u8 rng_buffer[SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES] 56 __cacheline_aligned; 57 58 static inline int hwrng_init(struct hwrng *rng) 59 { 60 if (!rng->init) 61 return 0; 62 return rng->init(rng); 63 } 64 65 static inline void hwrng_cleanup(struct hwrng *rng) 66 { 67 if (rng && rng->cleanup) 68 rng->cleanup(rng); 69 } 70 71 static int rng_dev_open(struct inode *inode, struct file *filp) 72 { 73 /* enforce read-only access to this chrdev */ 74 if ((filp->f_mode & FMODE_READ) == 0) 75 return -EINVAL; 76 if (filp->f_mode & FMODE_WRITE) 77 return -EINVAL; 78 return 0; 79 } 80 81 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, 82 int wait) { 83 int present; 84 85 if (rng->read) 86 return rng->read(rng, (void *)buffer, size, wait); 87 88 if (rng->data_present) 89 present = rng->data_present(rng, wait); 90 else 91 present = 1; 92 93 if (present) 94 return rng->data_read(rng, (u32 *)buffer); 95 96 return 0; 97 } 98 99 static ssize_t rng_dev_read(struct file *filp, char __user *buf, 100 size_t size, loff_t *offp) 101 { 102 ssize_t ret = 0; 103 int err = 0; 104 int bytes_read, len; 105 106 while (size) { 107 if (mutex_lock_interruptible(&rng_mutex)) { 108 err = -ERESTARTSYS; 109 goto out; 110 } 111 112 if (!current_rng) { 113 err = -ENODEV; 114 goto out_unlock; 115 } 116 117 if (!data_avail) { 118 bytes_read = rng_get_data(current_rng, rng_buffer, 119 sizeof(rng_buffer), 120 !(filp->f_flags & O_NONBLOCK)); 121 if (bytes_read < 0) { 122 err = bytes_read; 123 goto out_unlock; 124 } 125 data_avail = bytes_read; 126 } 127 128 if (!data_avail) { 129 if (filp->f_flags & O_NONBLOCK) { 130 err = -EAGAIN; 131 goto out_unlock; 132 } 133 } else { 134 len = data_avail; 135 if (len > size) 136 len = size; 137 138 data_avail -= len; 139 140 if (copy_to_user(buf + ret, rng_buffer + data_avail, 141 len)) { 142 err = -EFAULT; 143 goto out_unlock; 144 } 145 146 size -= len; 147 ret += len; 148 } 149 150 mutex_unlock(&rng_mutex); 151 152 if (need_resched()) 153 schedule_timeout_interruptible(1); 154 155 if (signal_pending(current)) { 156 err = -ERESTARTSYS; 157 goto out; 158 } 159 } 160 out: 161 return ret ? : err; 162 out_unlock: 163 mutex_unlock(&rng_mutex); 164 goto out; 165 } 166 167 168 static const struct file_operations rng_chrdev_ops = { 169 .owner = THIS_MODULE, 170 .open = rng_dev_open, 171 .read = rng_dev_read, 172 .llseek = noop_llseek, 173 }; 174 175 static struct miscdevice rng_miscdev = { 176 .minor = RNG_MISCDEV_MINOR, 177 .name = RNG_MODULE_NAME, 178 .nodename = "hwrng", 179 .fops = &rng_chrdev_ops, 180 }; 181 182 183 static ssize_t hwrng_attr_current_store(struct device *dev, 184 struct device_attribute *attr, 185 const char *buf, size_t len) 186 { 187 int err; 188 struct hwrng *rng; 189 190 err = mutex_lock_interruptible(&rng_mutex); 191 if (err) 192 return -ERESTARTSYS; 193 err = -ENODEV; 194 list_for_each_entry(rng, &rng_list, list) { 195 if (strcmp(rng->name, buf) == 0) { 196 if (rng == current_rng) { 197 err = 0; 198 break; 199 } 200 err = hwrng_init(rng); 201 if (err) 202 break; 203 hwrng_cleanup(current_rng); 204 current_rng = rng; 205 err = 0; 206 break; 207 } 208 } 209 mutex_unlock(&rng_mutex); 210 211 return err ? : len; 212 } 213 214 static ssize_t hwrng_attr_current_show(struct device *dev, 215 struct device_attribute *attr, 216 char *buf) 217 { 218 int err; 219 ssize_t ret; 220 const char *name = "none"; 221 222 err = mutex_lock_interruptible(&rng_mutex); 223 if (err) 224 return -ERESTARTSYS; 225 if (current_rng) 226 name = current_rng->name; 227 ret = snprintf(buf, PAGE_SIZE, "%s\n", name); 228 mutex_unlock(&rng_mutex); 229 230 return ret; 231 } 232 233 static ssize_t hwrng_attr_available_show(struct device *dev, 234 struct device_attribute *attr, 235 char *buf) 236 { 237 int err; 238 ssize_t ret = 0; 239 struct hwrng *rng; 240 241 err = mutex_lock_interruptible(&rng_mutex); 242 if (err) 243 return -ERESTARTSYS; 244 buf[0] = '\0'; 245 list_for_each_entry(rng, &rng_list, list) { 246 strncat(buf, rng->name, PAGE_SIZE - ret - 1); 247 ret += strlen(rng->name); 248 strncat(buf, " ", PAGE_SIZE - ret - 1); 249 ret++; 250 } 251 strncat(buf, "\n", PAGE_SIZE - ret - 1); 252 ret++; 253 mutex_unlock(&rng_mutex); 254 255 return ret; 256 } 257 258 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR, 259 hwrng_attr_current_show, 260 hwrng_attr_current_store); 261 static DEVICE_ATTR(rng_available, S_IRUGO, 262 hwrng_attr_available_show, 263 NULL); 264 265 266 static void unregister_miscdev(void) 267 { 268 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available); 269 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 270 misc_deregister(&rng_miscdev); 271 } 272 273 static int register_miscdev(void) 274 { 275 int err; 276 277 err = misc_register(&rng_miscdev); 278 if (err) 279 goto out; 280 err = device_create_file(rng_miscdev.this_device, 281 &dev_attr_rng_current); 282 if (err) 283 goto err_misc_dereg; 284 err = device_create_file(rng_miscdev.this_device, 285 &dev_attr_rng_available); 286 if (err) 287 goto err_remove_current; 288 out: 289 return err; 290 291 err_remove_current: 292 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 293 err_misc_dereg: 294 misc_deregister(&rng_miscdev); 295 goto out; 296 } 297 298 int hwrng_register(struct hwrng *rng) 299 { 300 int must_register_misc; 301 int err = -EINVAL; 302 struct hwrng *old_rng, *tmp; 303 304 if (rng->name == NULL || 305 (rng->data_read == NULL && rng->read == NULL)) 306 goto out; 307 308 mutex_lock(&rng_mutex); 309 310 /* Must not register two RNGs with the same name. */ 311 err = -EEXIST; 312 list_for_each_entry(tmp, &rng_list, list) { 313 if (strcmp(tmp->name, rng->name) == 0) 314 goto out_unlock; 315 } 316 317 must_register_misc = (current_rng == NULL); 318 old_rng = current_rng; 319 if (!old_rng) { 320 err = hwrng_init(rng); 321 if (err) 322 goto out_unlock; 323 current_rng = rng; 324 } 325 err = 0; 326 if (must_register_misc) { 327 err = register_miscdev(); 328 if (err) { 329 if (!old_rng) { 330 hwrng_cleanup(rng); 331 current_rng = NULL; 332 } 333 goto out_unlock; 334 } 335 } 336 INIT_LIST_HEAD(&rng->list); 337 list_add_tail(&rng->list, &rng_list); 338 out_unlock: 339 mutex_unlock(&rng_mutex); 340 out: 341 return err; 342 } 343 EXPORT_SYMBOL_GPL(hwrng_register); 344 345 void hwrng_unregister(struct hwrng *rng) 346 { 347 int err; 348 349 mutex_lock(&rng_mutex); 350 351 list_del(&rng->list); 352 if (current_rng == rng) { 353 hwrng_cleanup(rng); 354 if (list_empty(&rng_list)) { 355 current_rng = NULL; 356 } else { 357 current_rng = list_entry(rng_list.prev, struct hwrng, list); 358 err = hwrng_init(current_rng); 359 if (err) 360 current_rng = NULL; 361 } 362 } 363 if (list_empty(&rng_list)) 364 unregister_miscdev(); 365 366 mutex_unlock(&rng_mutex); 367 } 368 EXPORT_SYMBOL_GPL(hwrng_unregister); 369 370 371 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver"); 372 MODULE_LICENSE("GPL"); 373