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_unlock: 162 mutex_unlock(&rng_mutex); 163 out: 164 return ret ? : err; 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 }; 173 174 static struct miscdevice rng_miscdev = { 175 .minor = RNG_MISCDEV_MINOR, 176 .name = RNG_MODULE_NAME, 177 .nodename = "hwrng", 178 .fops = &rng_chrdev_ops, 179 }; 180 181 182 static ssize_t hwrng_attr_current_store(struct device *dev, 183 struct device_attribute *attr, 184 const char *buf, size_t len) 185 { 186 int err; 187 struct hwrng *rng; 188 189 err = mutex_lock_interruptible(&rng_mutex); 190 if (err) 191 return -ERESTARTSYS; 192 err = -ENODEV; 193 list_for_each_entry(rng, &rng_list, list) { 194 if (strcmp(rng->name, buf) == 0) { 195 if (rng == current_rng) { 196 err = 0; 197 break; 198 } 199 err = hwrng_init(rng); 200 if (err) 201 break; 202 hwrng_cleanup(current_rng); 203 current_rng = rng; 204 err = 0; 205 break; 206 } 207 } 208 mutex_unlock(&rng_mutex); 209 210 return err ? : len; 211 } 212 213 static ssize_t hwrng_attr_current_show(struct device *dev, 214 struct device_attribute *attr, 215 char *buf) 216 { 217 int err; 218 ssize_t ret; 219 const char *name = "none"; 220 221 err = mutex_lock_interruptible(&rng_mutex); 222 if (err) 223 return -ERESTARTSYS; 224 if (current_rng) 225 name = current_rng->name; 226 ret = snprintf(buf, PAGE_SIZE, "%s\n", name); 227 mutex_unlock(&rng_mutex); 228 229 return ret; 230 } 231 232 static ssize_t hwrng_attr_available_show(struct device *dev, 233 struct device_attribute *attr, 234 char *buf) 235 { 236 int err; 237 ssize_t ret = 0; 238 struct hwrng *rng; 239 240 err = mutex_lock_interruptible(&rng_mutex); 241 if (err) 242 return -ERESTARTSYS; 243 buf[0] = '\0'; 244 list_for_each_entry(rng, &rng_list, list) { 245 strncat(buf, rng->name, PAGE_SIZE - ret - 1); 246 ret += strlen(rng->name); 247 strncat(buf, " ", PAGE_SIZE - ret - 1); 248 ret++; 249 } 250 strncat(buf, "\n", PAGE_SIZE - ret - 1); 251 ret++; 252 mutex_unlock(&rng_mutex); 253 254 return ret; 255 } 256 257 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR, 258 hwrng_attr_current_show, 259 hwrng_attr_current_store); 260 static DEVICE_ATTR(rng_available, S_IRUGO, 261 hwrng_attr_available_show, 262 NULL); 263 264 265 static void unregister_miscdev(void) 266 { 267 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available); 268 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 269 misc_deregister(&rng_miscdev); 270 } 271 272 static int register_miscdev(void) 273 { 274 int err; 275 276 err = misc_register(&rng_miscdev); 277 if (err) 278 goto out; 279 err = device_create_file(rng_miscdev.this_device, 280 &dev_attr_rng_current); 281 if (err) 282 goto err_misc_dereg; 283 err = device_create_file(rng_miscdev.this_device, 284 &dev_attr_rng_available); 285 if (err) 286 goto err_remove_current; 287 out: 288 return err; 289 290 err_remove_current: 291 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 292 err_misc_dereg: 293 misc_deregister(&rng_miscdev); 294 goto out; 295 } 296 297 int hwrng_register(struct hwrng *rng) 298 { 299 int must_register_misc; 300 int err = -EINVAL; 301 struct hwrng *old_rng, *tmp; 302 303 if (rng->name == NULL || 304 (rng->data_read == NULL && rng->read == NULL)) 305 goto out; 306 307 mutex_lock(&rng_mutex); 308 309 /* Must not register two RNGs with the same name. */ 310 err = -EEXIST; 311 list_for_each_entry(tmp, &rng_list, list) { 312 if (strcmp(tmp->name, rng->name) == 0) 313 goto out_unlock; 314 } 315 316 must_register_misc = (current_rng == NULL); 317 old_rng = current_rng; 318 if (!old_rng) { 319 err = hwrng_init(rng); 320 if (err) 321 goto out_unlock; 322 current_rng = rng; 323 } 324 err = 0; 325 if (must_register_misc) { 326 err = register_miscdev(); 327 if (err) { 328 if (!old_rng) { 329 hwrng_cleanup(rng); 330 current_rng = NULL; 331 } 332 goto out_unlock; 333 } 334 } 335 INIT_LIST_HEAD(&rng->list); 336 list_add_tail(&rng->list, &rng_list); 337 out_unlock: 338 mutex_unlock(&rng_mutex); 339 out: 340 return err; 341 } 342 EXPORT_SYMBOL_GPL(hwrng_register); 343 344 void hwrng_unregister(struct hwrng *rng) 345 { 346 int err; 347 348 mutex_lock(&rng_mutex); 349 350 list_del(&rng->list); 351 if (current_rng == rng) { 352 hwrng_cleanup(rng); 353 if (list_empty(&rng_list)) { 354 current_rng = NULL; 355 } else { 356 current_rng = list_entry(rng_list.prev, struct hwrng, list); 357 err = hwrng_init(current_rng); 358 if (err) 359 current_rng = NULL; 360 } 361 } 362 if (list_empty(&rng_list)) 363 unregister_miscdev(); 364 365 mutex_unlock(&rng_mutex); 366 } 367 EXPORT_SYMBOL_GPL(hwrng_unregister); 368 369 370 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver"); 371 MODULE_LICENSE("GPL"); 372