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
  56
  57 static inline int hwrng_init(struct hwrng *rng)
  58 {
  59         if (!rng->init)
  60                 return 0;
  61         return rng->init(rng);
  62 }
  63
  64 static inline void hwrng_cleanup(struct hwrng *rng)
  65 {
  66         if (rng && rng->cleanup)
  67                 rng->cleanup(rng);
  68 }
  69
  70 static inline int hwrng_data_present(struct hwrng *rng, int wait)
  71 {
  72         if (!rng->data_present)
  73                 return 1;
  74         return rng->data_present(rng, wait);
  75 }
  76
  77 static inline int hwrng_data_read(struct hwrng *rng, u32 *data)
  78 {
  79         return rng->data_read(rng, data);
  80 }
  81
  82
  83 static int rng_dev_open(struct inode *inode, struct file *filp)
  84 {
  85         /* enforce read-only access to this chrdev */
  86         if ((filp->f_mode & FMODE_READ) == 0)
  87                 return -EINVAL;
  88         if (filp->f_mode & FMODE_WRITE)
  89                 return -EINVAL;
  90         cycle_kernel_lock();
  91         return 0;
  92 }
  93
  94 static ssize_t rng_dev_read(struct file *filp, char __user *buf,
  95                             size_t size, loff_t *offp)
  96 {
  97         u32 data;
  98         ssize_t ret = 0;
  99         int err = 0;
 100         int bytes_read;
 101
 102         while (size) {
 103                 err = -ERESTARTSYS;
 104                 if (mutex_lock_interruptible(&rng_mutex))
 105                         goto out;
 106                 if (!current_rng) {
 107                         mutex_unlock(&rng_mutex);
 108                         err = -ENODEV;
 109                         goto out;
 110                 }
 111
 112                 bytes_read = 0;
 113                 if (hwrng_data_present(current_rng,
 114                                        !(filp->f_flags & O_NONBLOCK)))
 115                         bytes_read = hwrng_data_read(current_rng, &data);
 116                 mutex_unlock(&rng_mutex);
 117
 118                 err = -EAGAIN;
 119                 if (!bytes_read && (filp->f_flags & O_NONBLOCK))
 120                         goto out;
 121                 if (bytes_read < 0) {
 122                         err = bytes_read;
 123                         goto out;
 124                 }
 125
 126                 err = -EFAULT;
 127                 while (bytes_read && size) {
 128                         if (put_user((u8)data, buf++))
 129                                 goto out;
 130                         size--;
 131                         ret++;
 132                         bytes_read--;
 133                         data >>= 8;
 134                 }
 135
 136                 if (need_resched())
 137                         schedule_timeout_interruptible(1);
 138                 err = -ERESTARTSYS;
 139                 if (signal_pending(current))
 140                         goto out;
 141         }
 142 out:
 143         return ret ? : err;
 144 }
 145
 146
 147 static const struct file_operations rng_chrdev_ops = {
 148         .owner          = THIS_MODULE,
 149         .open           = rng_dev_open,
 150         .read           = rng_dev_read,
 151 };
 152
 153 static struct miscdevice rng_miscdev = {
 154         .minor          = RNG_MISCDEV_MINOR,
 155         .name           = RNG_MODULE_NAME,
 156         .nodename       = "hwrng",
 157         .fops           = &rng_chrdev_ops,
 158 };
 159
 160
 161 static ssize_t hwrng_attr_current_store(struct device *dev,
 162                                         struct device_attribute *attr,
 163                                         const char *buf, size_t len)
 164 {
 165         int err;
 166         struct hwrng *rng;
 167
 168         err = mutex_lock_interruptible(&rng_mutex);
 169         if (err)
 170                 return -ERESTARTSYS;
 171         err = -ENODEV;
 172         list_for_each_entry(rng, &rng_list, list) {
 173                 if (strcmp(rng->name, buf) == 0) {
 174                         if (rng == current_rng) {
 175                                 err = 0;
 176                                 break;
 177                         }
 178                         err = hwrng_init(rng);
 179                         if (err)
 180                                 break;
 181                         hwrng_cleanup(current_rng);
 182                         current_rng = rng;
 183                         err = 0;
 184                         break;
 185                 }
 186         }
 187         mutex_unlock(&rng_mutex);
 188
 189         return err ? : len;
 190 }
 191
 192 static ssize_t hwrng_attr_current_show(struct device *dev,
 193                                        struct device_attribute *attr,
 194                                        char *buf)
 195 {
 196         int err;
 197         ssize_t ret;
 198         const char *name = "none";
 199
 200         err = mutex_lock_interruptible(&rng_mutex);
 201         if (err)
 202                 return -ERESTARTSYS;
 203         if (current_rng)
 204                 name = current_rng->name;
 205         ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
 206         mutex_unlock(&rng_mutex);
 207
 208         return ret;
 209 }
 210
 211 static ssize_t hwrng_attr_available_show(struct device *dev,
 212                                          struct device_attribute *attr,
 213                                          char *buf)
 214 {
 215         int err;
 216         ssize_t ret = 0;
 217         struct hwrng *rng;
 218
 219         err = mutex_lock_interruptible(&rng_mutex);
 220         if (err)
 221                 return -ERESTARTSYS;
 222         buf[0] = '\0';
 223         list_for_each_entry(rng, &rng_list, list) {
 224                 strncat(buf, rng->name, PAGE_SIZE - ret - 1);
 225                 ret += strlen(rng->name);
 226                 strncat(buf, " ", PAGE_SIZE - ret - 1);
 227                 ret++;
 228         }
 229         strncat(buf, "\n", PAGE_SIZE - ret - 1);
 230         ret++;
 231         mutex_unlock(&rng_mutex);
 232
 233         return ret;
 234 }
 235
 236 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
 237                    hwrng_attr_current_show,
 238                    hwrng_attr_current_store);
 239 static DEVICE_ATTR(rng_available, S_IRUGO,
 240                    hwrng_attr_available_show,
 241                    NULL);
 242
 243
 244 static void unregister_miscdev(void)
 245 {
 246         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
 247         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 248         misc_deregister(&rng_miscdev);
 249 }
 250
 251 static int register_miscdev(void)
 252 {
 253         int err;
 254
 255         err = misc_register(&rng_miscdev);
 256         if (err)
 257                 goto out;
 258         err = device_create_file(rng_miscdev.this_device,
 259                                  &dev_attr_rng_current);
 260         if (err)
 261                 goto err_misc_dereg;
 262         err = device_create_file(rng_miscdev.this_device,
 263                                  &dev_attr_rng_available);
 264         if (err)
 265                 goto err_remove_current;
 266 out:
 267         return err;
 268
 269 err_remove_current:
 270         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 271 err_misc_dereg:
 272         misc_deregister(&rng_miscdev);
 273         goto out;
 274 }
 275
 276 int hwrng_register(struct hwrng *rng)
 277 {
 278         int must_register_misc;
 279         int err = -EINVAL;
 280         struct hwrng *old_rng, *tmp;
 281
 282         if (rng->name == NULL ||
 283             rng->data_read == NULL)
 284                 goto out;
 285
 286         mutex_lock(&rng_mutex);
 287
 288         /* Must not register two RNGs with the same name. */
 289         err = -EEXIST;
 290         list_for_each_entry(tmp, &rng_list, list) {
 291                 if (strcmp(tmp->name, rng->name) == 0)
 292                         goto out_unlock;
 293         }
 294
 295         must_register_misc = (current_rng == NULL);
 296         old_rng = current_rng;
 297         if (!old_rng) {
 298                 err = hwrng_init(rng);
 299                 if (err)
 300                         goto out_unlock;
 301                 current_rng = rng;
 302         }
 303         err = 0;
 304         if (must_register_misc) {
 305                 err = register_miscdev();
 306                 if (err) {
 307                         if (!old_rng) {
 308                                 hwrng_cleanup(rng);
 309                                 current_rng = NULL;
 310                         }
 311                         goto out_unlock;
 312                 }
 313         }
 314         INIT_LIST_HEAD(&rng->list);
 315         list_add_tail(&rng->list, &rng_list);
 316 out_unlock:
 317         mutex_unlock(&rng_mutex);
 318 out:
 319         return err;
 320 }
 321 EXPORT_SYMBOL_GPL(hwrng_register);
 322
 323 void hwrng_unregister(struct hwrng *rng)
 324 {
 325         int err;
 326
 327         mutex_lock(&rng_mutex);
 328
 329         list_del(&rng->list);
 330         if (current_rng == rng) {
 331                 hwrng_cleanup(rng);
 332                 if (list_empty(&rng_list)) {
 333                         current_rng = NULL;
 334                 } else {
 335                         current_rng = list_entry(rng_list.prev, struct hwrng, list);
 336                         err = hwrng_init(current_rng);
 337                         if (err)
 338                                 current_rng = NULL;
 339                 }
 340         }
 341         if (list_empty(&rng_list))
 342                 unregister_miscdev();
 343
 344         mutex_unlock(&rng_mutex);
 345 }
 346 EXPORT_SYMBOL_GPL(hwrng_unregister);
 347
 348
 349 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
 350 MODULE_LICENSE("GPL");