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/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");