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 55 56 static inline int hwrng_init(struct hwrng *rng) 57 { 58 if (!rng->init) 59 return 0; 60 return rng->init(rng); 61 } 62 63 static inline void hwrng_cleanup(struct hwrng *rng) 64 { 65 if (rng && rng->cleanup) 66 rng->cleanup(rng); 67 } 68 69 static inline int hwrng_data_present(struct hwrng *rng, int wait) 70 { 71 if (!rng->data_present) 72 return 1; 73 return rng->data_present(rng, wait); 74 } 75 76 static inline int hwrng_data_read(struct hwrng *rng, u32 *data) 77 { 78 return rng->data_read(rng, data); 79 } 80 81 82 static int rng_dev_open(struct inode *inode, struct file *filp) 83 { 84 /* enforce read-only access to this chrdev */ 85 if ((filp->f_mode & FMODE_READ) == 0) 86 return -EINVAL; 87 if (filp->f_mode & FMODE_WRITE) 88 return -EINVAL; 89 return 0; 90 } 91 92 static ssize_t rng_dev_read(struct file *filp, char __user *buf, 93 size_t size, loff_t *offp) 94 { 95 u32 data; 96 ssize_t ret = 0; 97 int err = 0; 98 int bytes_read; 99 100 while (size) { 101 err = -ERESTARTSYS; 102 if (mutex_lock_interruptible(&rng_mutex)) 103 goto out; 104 if (!current_rng) { 105 mutex_unlock(&rng_mutex); 106 err = -ENODEV; 107 goto out; 108 } 109 110 bytes_read = 0; 111 if (hwrng_data_present(current_rng, 112 !(filp->f_flags & O_NONBLOCK))) 113 bytes_read = hwrng_data_read(current_rng, &data); 114 mutex_unlock(&rng_mutex); 115 116 err = -EAGAIN; 117 if (!bytes_read && (filp->f_flags & O_NONBLOCK)) 118 goto out; 119 120 err = -EFAULT; 121 while (bytes_read && size) { 122 if (put_user((u8)data, buf++)) 123 goto out; 124 size--; 125 ret++; 126 bytes_read--; 127 data >>= 8; 128 } 129 130 if (need_resched()) 131 schedule_timeout_interruptible(1); 132 err = -ERESTARTSYS; 133 if (signal_pending(current)) 134 goto out; 135 } 136 out: 137 return ret ? : err; 138 } 139 140 141 static const struct file_operations rng_chrdev_ops = { 142 .owner = THIS_MODULE, 143 .open = rng_dev_open, 144 .read = rng_dev_read, 145 }; 146 147 static struct miscdevice rng_miscdev = { 148 .minor = RNG_MISCDEV_MINOR, 149 .name = RNG_MODULE_NAME, 150 .fops = &rng_chrdev_ops, 151 }; 152 153 154 static ssize_t hwrng_attr_current_store(struct device *dev, 155 struct device_attribute *attr, 156 const char *buf, size_t len) 157 { 158 int err; 159 struct hwrng *rng; 160 161 err = mutex_lock_interruptible(&rng_mutex); 162 if (err) 163 return -ERESTARTSYS; 164 err = -ENODEV; 165 list_for_each_entry(rng, &rng_list, list) { 166 if (strcmp(rng->name, buf) == 0) { 167 if (rng == current_rng) { 168 err = 0; 169 break; 170 } 171 err = hwrng_init(rng); 172 if (err) 173 break; 174 hwrng_cleanup(current_rng); 175 current_rng = rng; 176 err = 0; 177 break; 178 } 179 } 180 mutex_unlock(&rng_mutex); 181 182 return err ? : len; 183 } 184 185 static ssize_t hwrng_attr_current_show(struct device *dev, 186 struct device_attribute *attr, 187 char *buf) 188 { 189 int err; 190 ssize_t ret; 191 const char *name = "none"; 192 193 err = mutex_lock_interruptible(&rng_mutex); 194 if (err) 195 return -ERESTARTSYS; 196 if (current_rng) 197 name = current_rng->name; 198 ret = snprintf(buf, PAGE_SIZE, "%s\n", name); 199 mutex_unlock(&rng_mutex); 200 201 return ret; 202 } 203 204 static ssize_t hwrng_attr_available_show(struct device *dev, 205 struct device_attribute *attr, 206 char *buf) 207 { 208 int err; 209 ssize_t ret = 0; 210 struct hwrng *rng; 211 212 err = mutex_lock_interruptible(&rng_mutex); 213 if (err) 214 return -ERESTARTSYS; 215 buf[0] = '\0'; 216 list_for_each_entry(rng, &rng_list, list) { 217 strncat(buf, rng->name, PAGE_SIZE - ret - 1); 218 ret += strlen(rng->name); 219 strncat(buf, " ", PAGE_SIZE - ret - 1); 220 ret++; 221 } 222 strncat(buf, "\n", PAGE_SIZE - ret - 1); 223 ret++; 224 mutex_unlock(&rng_mutex); 225 226 return ret; 227 } 228 229 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR, 230 hwrng_attr_current_show, 231 hwrng_attr_current_store); 232 static DEVICE_ATTR(rng_available, S_IRUGO, 233 hwrng_attr_available_show, 234 NULL); 235 236 237 static void unregister_miscdev(bool suspended) 238 { 239 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available); 240 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 241 __misc_deregister(&rng_miscdev, suspended); 242 } 243 244 static int register_miscdev(void) 245 { 246 int err; 247 248 err = misc_register(&rng_miscdev); 249 if (err) 250 goto out; 251 err = device_create_file(rng_miscdev.this_device, 252 &dev_attr_rng_current); 253 if (err) 254 goto err_misc_dereg; 255 err = device_create_file(rng_miscdev.this_device, 256 &dev_attr_rng_available); 257 if (err) 258 goto err_remove_current; 259 out: 260 return err; 261 262 err_remove_current: 263 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current); 264 err_misc_dereg: 265 misc_deregister(&rng_miscdev); 266 goto out; 267 } 268 269 int hwrng_register(struct hwrng *rng) 270 { 271 int must_register_misc; 272 int err = -EINVAL; 273 struct hwrng *old_rng, *tmp; 274 275 if (rng->name == NULL || 276 rng->data_read == NULL) 277 goto out; 278 279 mutex_lock(&rng_mutex); 280 281 /* Must not register two RNGs with the same name. */ 282 err = -EEXIST; 283 list_for_each_entry(tmp, &rng_list, list) { 284 if (strcmp(tmp->name, rng->name) == 0) 285 goto out_unlock; 286 } 287 288 must_register_misc = (current_rng == NULL); 289 old_rng = current_rng; 290 if (!old_rng) { 291 err = hwrng_init(rng); 292 if (err) 293 goto out_unlock; 294 current_rng = rng; 295 } 296 err = 0; 297 if (must_register_misc) { 298 err = register_miscdev(); 299 if (err) { 300 if (!old_rng) { 301 hwrng_cleanup(rng); 302 current_rng = NULL; 303 } 304 goto out_unlock; 305 } 306 } 307 INIT_LIST_HEAD(&rng->list); 308 list_add_tail(&rng->list, &rng_list); 309 out_unlock: 310 mutex_unlock(&rng_mutex); 311 out: 312 return err; 313 } 314 EXPORT_SYMBOL_GPL(hwrng_register); 315 316 void __hwrng_unregister(struct hwrng *rng, bool suspended) 317 { 318 int err; 319 320 mutex_lock(&rng_mutex); 321 322 list_del(&rng->list); 323 if (current_rng == rng) { 324 hwrng_cleanup(rng); 325 if (list_empty(&rng_list)) { 326 current_rng = NULL; 327 } else { 328 current_rng = list_entry(rng_list.prev, struct hwrng, list); 329 err = hwrng_init(current_rng); 330 if (err) 331 current_rng = NULL; 332 } 333 } 334 if (list_empty(&rng_list)) 335 unregister_miscdev(suspended); 336 337 mutex_unlock(&rng_mutex); 338 } 339 EXPORT_SYMBOL_GPL(__hwrng_unregister); 340 341 342 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver"); 343 MODULE_LICENSE("GPL"); 344