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/smp_lock.h> 41 #include <linux/init.h> 42 #include <linux/miscdevice.h> 43 #include <linux/delay.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[SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES] 57 __cacheline_aligned; 58 59 static inline int hwrng_init(struct hwrng *rng) 60 { 61 if (!rng->init) 62 return 0; 63 return rng->init(rng); 64 } 65 66 static inline void hwrng_cleanup(struct hwrng *rng) 67 { 68 if (rng && rng->cleanup) 69 rng->cleanup(rng); 70 } 71 72 static int rng_dev_open(struct inode *inode, struct file *filp) 73 { 74 /* enforce read-only access to this chrdev */ 75 if ((filp->f_mode & FMODE_READ) == 0) 76 return -EINVAL; 77 if (filp->f_mode & FMODE_WRITE) 78 return -EINVAL; 79 return 0; 80 } 81 82 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, 83 int wait) { 84 int present; 85 86 if (rng->read) 87 return rng->read(rng, (void *)buffer, size, wait); 88 89 if (rng->data_present) 90 present = rng->data_present(rng, wait); 91 else 92 present = 1; 93 94 if (present) 95 return rng->data_read(rng, (u32 *)buffer); 96 97 return 0; 98 } 99 100 static ssize_t rng_dev_read(struct file *filp, char __user *buf, 101 size_t size, loff_t *offp) 102 { 103 ssize_t ret = 0; 104 int err = 0; 105 int bytes_read, len; 106 107 while (size) { 108 if (mutex_lock_interruptible(&rng_mutex)) { 109 err = -ERESTARTSYS; 110 goto out; 111 } 112 113 if (!current_rng) { 114 err = -ENODEV; 115 goto out_unlock; 116 } 117 118 if (!data_avail) { 119 bytes_read = rng_get_data(current_rng, rng_buffer, 120 sizeof(rng_buffer), 121 !(filp->f_flags & O_NONBLOCK)); 122 if (bytes_read < 0) { 123 err = bytes_read; 124 goto out_unlock; 125 } 126 data_avail = bytes_read; 127 } 128 129 if (!data_avail) { 130 if (filp->f_flags & O_NONBLOCK) { 131 err = -EAGAIN; 132 goto out_unlock; 133 } 134 } else { 135 len = data_avail; 136 if (len > size) 137 len = size; 138 139 data_avail -= len; 140 141 if (copy_to_user(buf + ret, rng_buffer + data_avail, 142 len)) { 143 err = -EFAULT; 144 goto out_unlock; 145 } 146 147 size -= len; 148 ret += len; 149 } 150 151 mutex_unlock(&rng_mutex); 152 153 if (need_resched()) 154 schedule_timeout_interruptible(1); 155 156 if (signal_pending(current)) { 157 err = -ERESTARTSYS; 158 goto out; 159 } 160 } 161 out: 162 return ret ? : err; 163 out_unlock: 164 mutex_unlock(&rng_mutex); 165 goto out; 166 } 167 168 169 static const struct file_operations rng_chrdev_ops = { 170 .owner = THIS_MODULE, 171 .open = rng_dev_open, 172 .read = rng_dev_read, 173 .llseek = noop_llseek, 174 }; 175 176 static struct miscdevice rng_miscdev = { 177 .minor = RNG_MISCDEV_MINOR, 178 .name = RNG_MODULE_NAME, 179 .nodename = "hwrng", 180 .fops = &rng_chrdev_ops, 181 }; 182 183 184 static ssize_t hwrng_attr_current_store(struct device *dev, 185 struct device_attribute *attr, 186 const char *buf, size_t len) 187 { 188 int err; 189 struct hwrng *rng; 190 191 err = mutex_lock_interruptible(&rng_mutex); 192 if (err) 193 return -ERESTARTSYS; 194 err = -ENODEV; 195 list_for_each_entry(rng, &rng_list, list) { 196 if (strcmp(rng->name, buf) == 0) { 197 if (rng == current_rng) { 198 err = 0; 199 break; 200 } 201 err = hwrng_init(rng); 202 if (err) 203 break; 204 hwrng_cleanup(current_rng); 205 current_rng = rng; 206 err = 0; 207 break; 208 } 209 } 210 mutex_unlock(&rng_mutex); 211 212 return err ? : len; 213 } 214 215 static ssize_t hwrng_attr_current_show(struct device *dev, 216 struct device_attribute *attr, 217 char *buf) 218 { 219 int err; 220 ssize_t ret; 221 const char *name = "none"; 222 223 err = mutex_lock_interruptible(&rng_mutex); 224 if (err) 225 return -ERESTARTSYS; 226 if (current_rng) 227 name = current_rng->name; 228 ret = snprintf(buf, PAGE_SIZE, "%s\n", name); 229 mutex_unlock(&rng_mutex); 230 231 return ret; 232 } 233 234 static ssize_t hwrng_attr_available_show(struct device *dev, 235 struct device_attribute *attr, 236 char *buf) 237 { 238 int err; 239 ssize_t ret = 0; 240 struct hwrng *rng; 241 242 err = mutex_lock_interruptible(&rng_mutex); 243 if (err) 244 return -ERESTARTSYS; 245 buf[0] = '\0'; 246 list_for_each_entry(rng, &rng_list, list) { 247 strncat(buf, rng->name, PAGE_SIZE - ret - 1); 248 ret += strlen(rng->name); 249 strncat(buf, " ", PAGE_SIZE - ret - 1); 250 ret++; 251 } 252 strncat(buf, "\n", PAGE_SIZE - ret - 1); 253 ret++; 254 mutex_unlock(&rng_mutex); 255 256 return ret; 257 } 258 259 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR, 260 hwrng_attr_current_show, 261 hwrng_attr_current_store); 262 static DEVICE_ATTR(rng_available, S_IRUGO, 263 hwrng_attr_available_show, 264 NULL); 265 266 267 static void unregister_miscdev(void) 268 { 269 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available); 270 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 271 misc_deregister(&rng_miscdev); 272 } 273 274 static int register_miscdev(void) 275 { 276 int err; 277 278 err = misc_register(&rng_miscdev); 279 if (err) 280 goto out; 281 err = device_create_file(rng_miscdev.this_device, 282 &dev_attr_rng_current); 283 if (err) 284 goto err_misc_dereg; 285 err = device_create_file(rng_miscdev.this_device, 286 &dev_attr_rng_available); 287 if (err) 288 goto err_remove_current; 289 out: 290 return err; 291 292 err_remove_current: 293 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 294 err_misc_dereg: 295 misc_deregister(&rng_miscdev); 296 goto out; 297 } 298 299 int hwrng_register(struct hwrng *rng) 300 { 301 int must_register_misc; 302 int err = -EINVAL; 303 struct hwrng *old_rng, *tmp; 304 305 if (rng->name == NULL || 306 (rng->data_read == NULL && rng->read == NULL)) 307 goto out; 308 309 mutex_lock(&rng_mutex); 310 311 /* Must not register two RNGs with the same name. */ 312 err = -EEXIST; 313 list_for_each_entry(tmp, &rng_list, list) { 314 if (strcmp(tmp->name, rng->name) == 0) 315 goto out_unlock; 316 } 317 318 must_register_misc = (current_rng == NULL); 319 old_rng = current_rng; 320 if (!old_rng) { 321 err = hwrng_init(rng); 322 if (err) 323 goto out_unlock; 324 current_rng = rng; 325 } 326 err = 0; 327 if (must_register_misc) { 328 err = register_miscdev(); 329 if (err) { 330 if (!old_rng) { 331 hwrng_cleanup(rng); 332 current_rng = NULL; 333 } 334 goto out_unlock; 335 } 336 } 337 INIT_LIST_HEAD(&rng->list); 338 list_add_tail(&rng->list, &rng_list); 339 out_unlock: 340 mutex_unlock(&rng_mutex); 341 out: 342 return err; 343 } 344 EXPORT_SYMBOL_GPL(hwrng_register); 345 346 void hwrng_unregister(struct hwrng *rng) 347 { 348 int err; 349 350 mutex_lock(&rng_mutex); 351 352 list_del(&rng->list); 353 if (current_rng == rng) { 354 hwrng_cleanup(rng); 355 if (list_empty(&rng_list)) { 356 current_rng = NULL; 357 } else { 358 current_rng = list_entry(rng_list.prev, struct hwrng, list); 359 err = hwrng_init(current_rng); 360 if (err) 361 current_rng = NULL; 362 } 363 } 364 if (list_empty(&rng_list)) 365 unregister_miscdev(); 366 367 mutex_unlock(&rng_mutex); 368 } 369 EXPORT_SYMBOL_GPL(hwrng_unregister); 370 371 372 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver"); 373 MODULE_LICENSE("GPL"); 374