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         cycle_kernel_lock();
  80         return 0;
  81 }
  82
  83 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
  84                         int wait) {
  85         int present;
  86
  87         if (rng->read)
  88                 return rng->read(rng, (void *)buffer, size, wait);
  89
  90         if (rng->data_present)
  91                 present = rng->data_present(rng, wait);
  92         else
  93                 present = 1;
  94
  95         if (present)
  96                 return rng->data_read(rng, (u32 *)buffer);
  97
  98         return 0;
  99 }
 100
 101 static ssize_t rng_dev_read(struct file *filp, char __user *buf,
 102                             size_t size, loff_t *offp)
 103 {
 104         ssize_t ret = 0;
 105         int err = 0;
 106         int bytes_read, len;
 107
 108         while (size) {
 109                 if (mutex_lock_interruptible(&rng_mutex)) {
 110                         err = -ERESTARTSYS;
 111                         goto out;
 112                 }
 113
 114                 if (!current_rng) {
 115                         err = -ENODEV;
 116                         goto out_unlock;
 117                 }
 118
 119                 if (!data_avail) {
 120                         bytes_read = rng_get_data(current_rng, rng_buffer,
 121                                 sizeof(rng_buffer),
 122                                 !(filp->f_flags & O_NONBLOCK));
 123                         if (bytes_read < 0) {
 124                                 err = bytes_read;
 125                                 goto out_unlock;
 126                         }
 127                         data_avail = bytes_read;
 128                 }
 129
 130                 if (!data_avail) {
 131                         if (filp->f_flags & O_NONBLOCK) {
 132                                 err = -EAGAIN;
 133                                 goto out_unlock;
 134                         }
 135                 } else {
 136                         len = data_avail;
 137                         if (len > size)
 138                                 len = size;
 139
 140                         data_avail -= len;
 141
 142                         if (copy_to_user(buf + ret, rng_buffer + data_avail,
 143                                                                 len)) {
 144                                 err = -EFAULT;
 145                                 goto out_unlock;
 146                         }
 147
 148                         size -= len;
 149                         ret += len;
 150                 }
 151
 152                 mutex_unlock(&rng_mutex);
 153
 154                 if (need_resched())
 155                         schedule_timeout_interruptible(1);
 156
 157                 if (signal_pending(current)) {
 158                         err = -ERESTARTSYS;
 159                         goto out;
 160                 }
 161         }
 162 out_unlock:
 163         mutex_unlock(&rng_mutex);
 164 out:
 165         return ret ? : err;
 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 };
 174
 175 static struct miscdevice rng_miscdev = {
 176         .minor          = RNG_MISCDEV_MINOR,
 177         .name           = RNG_MODULE_NAME,
 178         .nodename       = "hwrng",
 179         .fops           = &rng_chrdev_ops,
 180 };
 181
 182
 183 static ssize_t hwrng_attr_current_store(struct device *dev,
 184                                         struct device_attribute *attr,
 185                                         const char *buf, size_t len)
 186 {
 187         int err;
 188         struct hwrng *rng;
 189
 190         err = mutex_lock_interruptible(&rng_mutex);
 191         if (err)
 192                 return -ERESTARTSYS;
 193         err = -ENODEV;
 194         list_for_each_entry(rng, &rng_list, list) {
 195                 if (strcmp(rng->name, buf) == 0) {
 196                         if (rng == current_rng) {
 197                                 err = 0;
 198                                 break;
 199                         }
 200                         err = hwrng_init(rng);
 201                         if (err)
 202                                 break;
 203                         hwrng_cleanup(current_rng);
 204                         current_rng = rng;
 205                         err = 0;
 206                         break;
 207                 }
 208         }
 209         mutex_unlock(&rng_mutex);
 210
 211         return err ? : len;
 212 }
 213
 214 static ssize_t hwrng_attr_current_show(struct device *dev,
 215                                        struct device_attribute *attr,
 216                                        char *buf)
 217 {
 218         int err;
 219         ssize_t ret;
 220         const char *name = "none";
 221
 222         err = mutex_lock_interruptible(&rng_mutex);
 223         if (err)
 224                 return -ERESTARTSYS;
 225         if (current_rng)
 226                 name = current_rng->name;
 227         ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
 228         mutex_unlock(&rng_mutex);
 229
 230         return ret;
 231 }
 232
 233 static ssize_t hwrng_attr_available_show(struct device *dev,
 234                                          struct device_attribute *attr,
 235                                          char *buf)
 236 {
 237         int err;
 238         ssize_t ret = 0;
 239         struct hwrng *rng;
 240
 241         err = mutex_lock_interruptible(&rng_mutex);
 242         if (err)
 243                 return -ERESTARTSYS;
 244         buf[0] = '\0';
 245         list_for_each_entry(rng, &rng_list, list) {
 246                 strncat(buf, rng->name, PAGE_SIZE - ret - 1);
 247                 ret += strlen(rng->name);
 248                 strncat(buf, " ", PAGE_SIZE - ret - 1);
 249                 ret++;
 250         }
 251         strncat(buf, "\n", PAGE_SIZE - ret - 1);
 252         ret++;
 253         mutex_unlock(&rng_mutex);
 254
 255         return ret;
 256 }
 257
 258 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
 259                    hwrng_attr_current_show,
 260                    hwrng_attr_current_store);
 261 static DEVICE_ATTR(rng_available, S_IRUGO,
 262                    hwrng_attr_available_show,
 263                    NULL);
 264
 265
 266 static void unregister_miscdev(void)
 267 {
 268         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
 269         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 270         misc_deregister(&rng_miscdev);
 271 }
 272
 273 static int register_miscdev(void)
 274 {
 275         int err;
 276
 277         err = misc_register(&rng_miscdev);
 278         if (err)
 279                 goto out;
 280         err = device_create_file(rng_miscdev.this_device,
 281                                  &dev_attr_rng_current);
 282         if (err)
 283                 goto err_misc_dereg;
 284         err = device_create_file(rng_miscdev.this_device,
 285                                  &dev_attr_rng_available);
 286         if (err)
 287                 goto err_remove_current;
 288 out:
 289         return err;
 290
 291 err_remove_current:
 292         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 293 err_misc_dereg:
 294         misc_deregister(&rng_miscdev);
 295         goto out;
 296 }
 297
 298 int hwrng_register(struct hwrng *rng)
 299 {
 300         int must_register_misc;
 301         int err = -EINVAL;
 302         struct hwrng *old_rng, *tmp;
 303
 304         if (rng->name == NULL ||
 305             (rng->data_read == NULL && rng->read == NULL))
 306                 goto out;
 307
 308         mutex_lock(&rng_mutex);
 309
 310         /* Must not register two RNGs with the same name. */
 311         err = -EEXIST;
 312         list_for_each_entry(tmp, &rng_list, list) {
 313                 if (strcmp(tmp->name, rng->name) == 0)
 314                         goto out_unlock;
 315         }
 316
 317         must_register_misc = (current_rng == NULL);
 318         old_rng = current_rng;
 319         if (!old_rng) {
 320                 err = hwrng_init(rng);
 321                 if (err)
 322                         goto out_unlock;
 323                 current_rng = rng;
 324         }
 325         err = 0;
 326         if (must_register_misc) {
 327                 err = register_miscdev();
 328                 if (err) {
 329                         if (!old_rng) {
 330                                 hwrng_cleanup(rng);
 331                                 current_rng = NULL;
 332                         }
 333                         goto out_unlock;
 334                 }
 335         }
 336         INIT_LIST_HEAD(&rng->list);
 337         list_add_tail(&rng->list, &rng_list);
 338 out_unlock:
 339         mutex_unlock(&rng_mutex);
 340 out:
 341         return err;
 342 }
 343 EXPORT_SYMBOL_GPL(hwrng_register);
 344
 345 void hwrng_unregister(struct hwrng *rng)
 346 {
 347         int err;
 348
 349         mutex_lock(&rng_mutex);
 350
 351         list_del(&rng->list);
 352         if (current_rng == rng) {
 353                 hwrng_cleanup(rng);
 354                 if (list_empty(&rng_list)) {
 355                         current_rng = NULL;
 356                 } else {
 357                         current_rng = list_entry(rng_list.prev, struct hwrng, list);
 358                         err = hwrng_init(current_rng);
 359                         if (err)
 360                                 current_rng = NULL;
 361                 }
 362         }
 363         if (list_empty(&rng_list))
 364                 unregister_miscdev();
 365
 366         mutex_unlock(&rng_mutex);
 367 }
 368 EXPORT_SYMBOL_GPL(hwrng_unregister);
 369
 370
 371 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
 372 MODULE_LICENSE("GPL");