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 < 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");