drivers/char/hw_random/core.c

   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] __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         cycle_kernel_lock();
  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");