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)
  70 {
  71         if (!rng->data_present)
  72                 return 1;
  73         return rng->data_present(rng);
  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 i, err = 0;
  98         int data_present;
  99         int bytes_read;
 100
 101         while (size) {
 102                 err = -ERESTARTSYS;
 103                 if (mutex_lock_interruptible(&rng_mutex))
 104                         goto out;
 105                 if (!current_rng) {
 106                         mutex_unlock(&rng_mutex);
 107                         err = -ENODEV;
 108                         goto out;
 109                 }
 110                 if (filp->f_flags & O_NONBLOCK) {
 111                         data_present = hwrng_data_present(current_rng);
 112                 } else {
 113                         /* Some RNG require some time between data_reads to gather
 114                          * new entropy. Poll it.
 115                          */
 116                         for (i = 0; i < 20; i++) {
 117                                 data_present = hwrng_data_present(current_rng);
 118                                 if (data_present)
 119                                         break;
 120                                 udelay(10);
 121                         }
 122                 }
 123                 bytes_read = 0;
 124                 if (data_present)
 125                         bytes_read = hwrng_data_read(current_rng, &data);
 126                 mutex_unlock(&rng_mutex);
 127
 128                 err = -EAGAIN;
 129                 if (!bytes_read && (filp->f_flags & O_NONBLOCK))
 130                         goto out;
 131
 132                 err = -EFAULT;
 133                 while (bytes_read && size) {
 134                         if (put_user((u8)data, buf++))
 135                                 goto out;
 136                         size--;
 137                         ret++;
 138                         bytes_read--;
 139                         data >>= 8;
 140                 }
 141
 142                 if (need_resched())
 143                         schedule_timeout_interruptible(1);
 144                 err = -ERESTARTSYS;
 145                 if (signal_pending(current))
 146                         goto out;
 147         }
 148 out:
 149         return ret ? : err;
 150 }
 151
 152
 153 static const struct file_operations rng_chrdev_ops = {
 154         .owner          = THIS_MODULE,
 155         .open           = rng_dev_open,
 156         .read           = rng_dev_read,
 157 };
 158
 159 static struct miscdevice rng_miscdev = {
 160         .minor          = RNG_MISCDEV_MINOR,
 161         .name           = RNG_MODULE_NAME,
 162         .fops           = &rng_chrdev_ops,
 163 };
 164
 165
 166 static ssize_t hwrng_attr_current_store(struct device *dev,
 167                                         struct device_attribute *attr,
 168                                         const char *buf, size_t len)
 169 {
 170         int err;
 171         struct hwrng *rng;
 172
 173         err = mutex_lock_interruptible(&rng_mutex);
 174         if (err)
 175                 return -ERESTARTSYS;
 176         err = -ENODEV;
 177         list_for_each_entry(rng, &rng_list, list) {
 178                 if (strcmp(rng->name, buf) == 0) {
 179                         if (rng == current_rng) {
 180                                 err = 0;
 181                                 break;
 182                         }
 183                         err = hwrng_init(rng);
 184                         if (err)
 185                                 break;
 186                         hwrng_cleanup(current_rng);
 187                         current_rng = rng;
 188                         err = 0;
 189                         break;
 190                 }
 191         }
 192         mutex_unlock(&rng_mutex);
 193
 194         return err ? : len;
 195 }
 196
 197 static ssize_t hwrng_attr_current_show(struct device *dev,
 198                                        struct device_attribute *attr,
 199                                        char *buf)
 200 {
 201         int err;
 202         ssize_t ret;
 203         const char *name = "none";
 204
 205         err = mutex_lock_interruptible(&rng_mutex);
 206         if (err)
 207                 return -ERESTARTSYS;
 208         if (current_rng)
 209                 name = current_rng->name;
 210         ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
 211         mutex_unlock(&rng_mutex);
 212
 213         return ret;
 214 }
 215
 216 static ssize_t hwrng_attr_available_show(struct device *dev,
 217                                          struct device_attribute *attr,
 218                                          char *buf)
 219 {
 220         int err;
 221         ssize_t ret = 0;
 222         struct hwrng *rng;
 223
 224         err = mutex_lock_interruptible(&rng_mutex);
 225         if (err)
 226                 return -ERESTARTSYS;
 227         buf[0] = '\0';
 228         list_for_each_entry(rng, &rng_list, list) {
 229                 strncat(buf, rng->name, PAGE_SIZE - ret - 1);
 230                 ret += strlen(rng->name);
 231                 strncat(buf, " ", PAGE_SIZE - ret - 1);
 232                 ret++;
 233         }
 234         strncat(buf, "\n", PAGE_SIZE - ret - 1);
 235         ret++;
 236         mutex_unlock(&rng_mutex);
 237
 238         return ret;
 239 }
 240
 241 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
 242                    hwrng_attr_current_show,
 243                    hwrng_attr_current_store);
 244 static DEVICE_ATTR(rng_available, S_IRUGO,
 245                    hwrng_attr_available_show,
 246                    NULL);
 247
 248
 249 static void unregister_miscdev(void)
 250 {
 251         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
 252         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 253         misc_deregister(&rng_miscdev);
 254 }
 255
 256 static int register_miscdev(void)
 257 {
 258         int err;
 259
 260         err = misc_register(&rng_miscdev);
 261         if (err)
 262                 goto out;
 263         err = device_create_file(rng_miscdev.this_device,
 264                                  &dev_attr_rng_current);
 265         if (err)
 266                 goto err_misc_dereg;
 267         err = device_create_file(rng_miscdev.this_device,
 268                                  &dev_attr_rng_available);
 269         if (err)
 270                 goto err_remove_current;
 271 out:
 272         return err;
 273
 274 err_remove_current:
 275         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 276 err_misc_dereg:
 277         misc_deregister(&rng_miscdev);
 278         goto out;
 279 }
 280
 281 int hwrng_register(struct hwrng *rng)
 282 {
 283         int must_register_misc;
 284         int err = -EINVAL;
 285         struct hwrng *old_rng, *tmp;
 286
 287         if (rng->name == NULL ||
 288             rng->data_read == NULL)
 289                 goto out;
 290
 291         mutex_lock(&rng_mutex);
 292
 293         /* Must not register two RNGs with the same name. */
 294         err = -EEXIST;
 295         list_for_each_entry(tmp, &rng_list, list) {
 296                 if (strcmp(tmp->name, rng->name) == 0)
 297                         goto out_unlock;
 298         }
 299
 300         must_register_misc = (current_rng == NULL);
 301         old_rng = current_rng;
 302         if (!old_rng) {
 303                 err = hwrng_init(rng);
 304                 if (err)
 305                         goto out_unlock;
 306                 current_rng = rng;
 307         }
 308         err = 0;
 309         if (must_register_misc) {
 310                 err = register_miscdev();
 311                 if (err) {
 312                         if (!old_rng) {
 313                                 hwrng_cleanup(rng);
 314                                 current_rng = NULL;
 315                         }
 316                         goto out_unlock;
 317                 }
 318         }
 319         INIT_LIST_HEAD(&rng->list);
 320         list_add_tail(&rng->list, &rng_list);
 321 out_unlock:
 322         mutex_unlock(&rng_mutex);
 323 out:
 324         return err;
 325 }
 326 EXPORT_SYMBOL_GPL(hwrng_register);
 327
 328 void hwrng_unregister(struct hwrng *rng)
 329 {
 330         int err;
 331
 332         mutex_lock(&rng_mutex);
 333
 334         list_del(&rng->list);
 335         if (current_rng == rng) {
 336                 hwrng_cleanup(rng);
 337                 if (list_empty(&rng_list)) {
 338                         current_rng = NULL;
 339                 } else {
 340                         current_rng = list_entry(rng_list.prev, struct hwrng, list);
 341                         err = hwrng_init(current_rng);
 342                         if (err)
 343                                 current_rng = NULL;
 344                 }
 345         }
 346         if (list_empty(&rng_list))
 347                 unregister_miscdev();
 348
 349         mutex_unlock(&rng_mutex);
 350 }
 351 EXPORT_SYMBOL_GPL(hwrng_unregister);
 352
 353
 354 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
 355 MODULE_LICENSE("GPL");