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 <m@bues.ch>
  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/miscdevice.h>
  41 #include <linux/delay.h>
  42 #include <linux/slab.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 static int data_avail;
  55 static u8 *rng_buffer;
  56
  57 static size_t rng_buffer_size(void)
  58 {
  59         return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
  60 }
  61
  62 static inline int hwrng_init(struct hwrng *rng)
  63 {
  64         if (!rng->init)
  65                 return 0;
  66         return rng->init(rng);
  67 }
  68
  69 static inline void hwrng_cleanup(struct hwrng *rng)
  70 {
  71         if (rng && rng->cleanup)
  72                 rng->cleanup(rng);
  73 }
  74
  75 static int rng_dev_open(struct inode *inode, struct file *filp)
  76 {
  77         /* enforce read-only access to this chrdev */
  78         if ((filp->f_mode & FMODE_READ) == 0)
  79                 return -EINVAL;
  80         if (filp->f_mode & FMODE_WRITE)
  81                 return -EINVAL;
  82         return 0;
  83 }
  84
  85 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
  86                         int wait) {
  87         int present;
  88
  89         if (rng->read)
  90                 return rng->read(rng, (void *)buffer, size, wait);
  91
  92         if (rng->data_present)
  93                 present = rng->data_present(rng, wait);
  94         else
  95                 present = 1;
  96
  97         if (present)
  98                 return rng->data_read(rng, (u32 *)buffer);
  99
 100         return 0;
 101 }
 102
 103 static ssize_t rng_dev_read(struct file *filp, char __user *buf,
 104                             size_t size, loff_t *offp)
 105 {
 106         ssize_t ret = 0;
 107         int err = 0;
 108         int bytes_read, len;
 109
 110         while (size) {
 111                 if (mutex_lock_interruptible(&rng_mutex)) {
 112                         err = -ERESTARTSYS;
 113                         goto out;
 114                 }
 115
 116                 if (!current_rng) {
 117                         err = -ENODEV;
 118                         goto out_unlock;
 119                 }
 120
 121                 if (!data_avail) {
 122                         bytes_read = rng_get_data(current_rng, rng_buffer,
 123                                 rng_buffer_size(),
 124                                 !(filp->f_flags & O_NONBLOCK));
 125                         if (bytes_read < 0) {
 126                                 err = bytes_read;
 127                                 goto out_unlock;
 128                         }
 129                         data_avail = bytes_read;
 130                 }
 131
 132                 if (!data_avail) {
 133                         if (filp->f_flags & O_NONBLOCK) {
 134                                 err = -EAGAIN;
 135                                 goto out_unlock;
 136                         }
 137                 } else {
 138                         len = data_avail;
 139                         if (len > size)
 140                                 len = size;
 141
 142                         data_avail -= len;
 143
 144                         if (copy_to_user(buf + ret, rng_buffer + data_avail,
 145                                                                 len)) {
 146                                 err = -EFAULT;
 147                                 goto out_unlock;
 148                         }
 149
 150                         size -= len;
 151                         ret += len;
 152                 }
 153
 154                 mutex_unlock(&rng_mutex);
 155
 156                 if (need_resched())
 157                         schedule_timeout_interruptible(1);
 158
 159                 if (signal_pending(current)) {
 160                         err = -ERESTARTSYS;
 161                         goto out;
 162                 }
 163         }
 164 out:
 165         return ret ? : err;
 166 out_unlock:
 167         mutex_unlock(&rng_mutex);
 168         goto out;
 169 }
 170
 171
 172 static const struct file_operations rng_chrdev_ops = {
 173         .owner          = THIS_MODULE,
 174         .open           = rng_dev_open,
 175         .read           = rng_dev_read,
 176         .llseek         = noop_llseek,
 177 };
 178
 179 static struct miscdevice rng_miscdev = {
 180         .minor          = RNG_MISCDEV_MINOR,
 181         .name           = RNG_MODULE_NAME,
 182         .nodename       = "hwrng",
 183         .fops           = &rng_chrdev_ops,
 184 };
 185
 186
 187 static ssize_t hwrng_attr_current_store(struct device *dev,
 188                                         struct device_attribute *attr,
 189                                         const char *buf, size_t len)
 190 {
 191         int err;
 192         struct hwrng *rng;
 193
 194         err = mutex_lock_interruptible(&rng_mutex);
 195         if (err)
 196                 return -ERESTARTSYS;
 197         err = -ENODEV;
 198         list_for_each_entry(rng, &rng_list, list) {
 199                 if (strcmp(rng->name, buf) == 0) {
 200                         if (rng == current_rng) {
 201                                 err = 0;
 202                                 break;
 203                         }
 204                         err = hwrng_init(rng);
 205                         if (err)
 206                                 break;
 207                         hwrng_cleanup(current_rng);
 208                         current_rng = rng;
 209                         err = 0;
 210                         break;
 211                 }
 212         }
 213         mutex_unlock(&rng_mutex);
 214
 215         return err ? : len;
 216 }
 217
 218 static ssize_t hwrng_attr_current_show(struct device *dev,
 219                                        struct device_attribute *attr,
 220                                        char *buf)
 221 {
 222         int err;
 223         ssize_t ret;
 224         const char *name = "none";
 225
 226         err = mutex_lock_interruptible(&rng_mutex);
 227         if (err)
 228                 return -ERESTARTSYS;
 229         if (current_rng)
 230                 name = current_rng->name;
 231         ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
 232         mutex_unlock(&rng_mutex);
 233
 234         return ret;
 235 }
 236
 237 static ssize_t hwrng_attr_available_show(struct device *dev,
 238                                          struct device_attribute *attr,
 239                                          char *buf)
 240 {
 241         int err;
 242         ssize_t ret = 0;
 243         struct hwrng *rng;
 244
 245         err = mutex_lock_interruptible(&rng_mutex);
 246         if (err)
 247                 return -ERESTARTSYS;
 248         buf[0] = '\0';
 249         list_for_each_entry(rng, &rng_list, list) {
 250                 strncat(buf, rng->name, PAGE_SIZE - ret - 1);
 251                 ret += strlen(rng->name);
 252                 strncat(buf, " ", PAGE_SIZE - ret - 1);
 253                 ret++;
 254         }
 255         strncat(buf, "\n", PAGE_SIZE - ret - 1);
 256         ret++;
 257         mutex_unlock(&rng_mutex);
 258
 259         return ret;
 260 }
 261
 262 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
 263                    hwrng_attr_current_show,
 264                    hwrng_attr_current_store);
 265 static DEVICE_ATTR(rng_available, S_IRUGO,
 266                    hwrng_attr_available_show,
 267                    NULL);
 268
 269
 270 static void unregister_miscdev(void)
 271 {
 272         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
 273         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 274         misc_deregister(&rng_miscdev);
 275 }
 276
 277 static int register_miscdev(void)
 278 {
 279         int err;
 280
 281         err = misc_register(&rng_miscdev);
 282         if (err)
 283                 goto out;
 284         err = device_create_file(rng_miscdev.this_device,
 285                                  &dev_attr_rng_current);
 286         if (err)
 287                 goto err_misc_dereg;
 288         err = device_create_file(rng_miscdev.this_device,
 289                                  &dev_attr_rng_available);
 290         if (err)
 291                 goto err_remove_current;
 292 out:
 293         return err;
 294
 295 err_remove_current:
 296         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
 297 err_misc_dereg:
 298         misc_deregister(&rng_miscdev);
 299         goto out;
 300 }
 301
 302 int hwrng_register(struct hwrng *rng)
 303 {
 304         int must_register_misc;
 305         int err = -EINVAL;
 306         struct hwrng *old_rng, *tmp;
 307
 308         if (rng->name == NULL ||
 309             (rng->data_read == NULL && rng->read == NULL))
 310                 goto out;
 311
 312         mutex_lock(&rng_mutex);
 313
 314         /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
 315         err = -ENOMEM;
 316         if (!rng_buffer) {
 317                 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
 318                 if (!rng_buffer)
 319                         goto out_unlock;
 320         }
 321
 322         /* Must not register two RNGs with the same name. */
 323         err = -EEXIST;
 324         list_for_each_entry(tmp, &rng_list, list) {
 325                 if (strcmp(tmp->name, rng->name) == 0)
 326                         goto out_unlock;
 327         }
 328
 329         must_register_misc = (current_rng == NULL);
 330         old_rng = current_rng;
 331         if (!old_rng) {
 332                 err = hwrng_init(rng);
 333                 if (err)
 334                         goto out_unlock;
 335                 current_rng = rng;
 336         }
 337         err = 0;
 338         if (must_register_misc) {
 339                 err = register_miscdev();
 340                 if (err) {
 341                         if (!old_rng) {
 342                                 hwrng_cleanup(rng);
 343                                 current_rng = NULL;
 344                         }
 345                         goto out_unlock;
 346                 }
 347         }
 348         INIT_LIST_HEAD(&rng->list);
 349         list_add_tail(&rng->list, &rng_list);
 350 out_unlock:
 351         mutex_unlock(&rng_mutex);
 352 out:
 353         return err;
 354 }
 355 EXPORT_SYMBOL_GPL(hwrng_register);
 356
 357 void hwrng_unregister(struct hwrng *rng)
 358 {
 359         int err;
 360
 361         mutex_lock(&rng_mutex);
 362
 363         list_del(&rng->list);
 364         if (current_rng == rng) {
 365                 hwrng_cleanup(rng);
 366                 if (list_empty(&rng_list)) {
 367                         current_rng = NULL;
 368                 } else {
 369                         current_rng = list_entry(rng_list.prev, struct hwrng, list);
 370                         err = hwrng_init(current_rng);
 371                         if (err)
 372                                 current_rng = NULL;
 373                 }
 374         }
 375         if (list_empty(&rng_list))
 376                 unregister_miscdev();
 377
 378         mutex_unlock(&rng_mutex);
 379 }
 380 EXPORT_SYMBOL_GPL(hwrng_unregister);
 381
 382 static void __exit hwrng_exit(void)
 383 {
 384         mutex_lock(&rng_mutex);
 385         BUG_ON(current_rng);
 386         kfree(rng_buffer);
 387         mutex_unlock(&rng_mutex);
 388 }
 389
 390 module_exit(hwrng_exit);
 391
 392 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
 393 MODULE_LICENSE("GPL");