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