arch/um/drivers/random.c

   1 /* Copyright (C) 2005 - 2008 Jeff Dike <jdike@{linux.intel,addtoit}.com> */
   2
   3 /* Much of this ripped from drivers/char/hw_random.c, see there for other
   4  * copyright.
   5  *
   6  * This software may be used and distributed according to the terms
   7  * of the GNU General Public License, incorporated herein by reference.
   8  */
   9 #include <linux/sched.h>
  10 #include <linux/module.h>
  11 #include <linux/fs.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/miscdevice.h>
  14 #include <linux/delay.h>
  15 #include <asm/uaccess.h>
  16 #include "irq_kern.h"
  17 #include "os.h"
  18
  19 /*
  20  * core module and version information
  21  */
  22 #define RNG_VERSION "1.0.0"
  23 #define RNG_MODULE_NAME "hw_random"
  24
  25 #define RNG_MISCDEV_MINOR               183 /* official */
  26
  27 /* Changed at init time, in the non-modular case, and at module load
  28  * time, in the module case.  Presumably, the module subsystem
  29  * protects against a module being loaded twice at the same time.
  30  */
  31 static int random_fd = -1;
  32 static DECLARE_WAIT_QUEUE_HEAD(host_read_wait);
  33
  34 static int rng_dev_open (struct inode *inode, struct file *filp)
  35 {
  36         /* enforce read-only access to this chrdev */
  37         if ((filp->f_mode & FMODE_READ) == 0)
  38                 return -EINVAL;
  39         if ((filp->f_mode & FMODE_WRITE) != 0)
  40                 return -EINVAL;
  41
  42         return 0;
  43 }
  44
  45 static atomic_t host_sleep_count = ATOMIC_INIT(0);
  46
  47 static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
  48                              loff_t *offp)
  49 {
  50         u32 data;
  51         int n, ret = 0, have_data;
  52
  53         while (size) {
  54                 n = os_read_file(random_fd, &data, sizeof(data));
  55                 if (n > 0) {
  56                         have_data = n;
  57                         while (have_data && size) {
  58                                 if (put_user((u8) data, buf++)) {
  59                                         ret = ret ? : -EFAULT;
  60                                         break;
  61                                 }
  62                                 size--;
  63                                 ret++;
  64                                 have_data--;
  65                                 data >>= 8;
  66                         }
  67                 }
  68                 else if (n == -EAGAIN) {
  69                         DECLARE_WAITQUEUE(wait, current);
  70
  71                         if (filp->f_flags & O_NONBLOCK)
  72                                 return ret ? : -EAGAIN;
  73
  74                         atomic_inc(&host_sleep_count);
  75                         reactivate_fd(random_fd, RANDOM_IRQ);
  76                         add_sigio_fd(random_fd);
  77
  78                         add_wait_queue(&host_read_wait, &wait);
  79                         set_task_state(current, TASK_INTERRUPTIBLE);
  80
  81                         schedule();
  82                         set_task_state(current, TASK_RUNNING);
  83                         remove_wait_queue(&host_read_wait, &wait);
  84
  85                         if (atomic_dec_and_test(&host_sleep_count)) {
  86                                 ignore_sigio_fd(random_fd);
  87                                 deactivate_fd(random_fd, RANDOM_IRQ);
  88                         }
  89                 }
  90                 else
  91                         return n;
  92
  93                 if (signal_pending (current))
  94                         return ret ? : -ERESTARTSYS;
  95         }
  96         return ret;
  97 }
  98
  99 static const struct file_operations rng_chrdev_ops = {
 100         .owner          = THIS_MODULE,
 101         .open           = rng_dev_open,
 102         .read           = rng_dev_read,
 103         .llseek         = noop_llseek,
 104 };
 105
 106 /* rng_init shouldn't be called more than once at boot time */
 107 static struct miscdevice rng_miscdev = {
 108         RNG_MISCDEV_MINOR,
 109         RNG_MODULE_NAME,
 110         &rng_chrdev_ops,
 111 };
 112
 113 static irqreturn_t random_interrupt(int irq, void *data)
 114 {
 115         wake_up(&host_read_wait);
 116
 117         return IRQ_HANDLED;
 118 }
 119
 120 /*
 121  * rng_init - initialize RNG module
 122  */
 123 static int __init rng_init (void)
 124 {
 125         int err;
 126
 127         err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
 128         if (err < 0)
 129                 goto out;
 130
 131         random_fd = err;
 132
 133         err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt,
 134                              IRQF_DISABLED | IRQF_SAMPLE_RANDOM, "random",
 135                              NULL);
 136         if (err)
 137                 goto err_out_cleanup_hw;
 138
 139         sigio_broken(random_fd, 1);
 140
 141         err = misc_register (&rng_miscdev);
 142         if (err) {
 143                 printk (KERN_ERR RNG_MODULE_NAME ": misc device register "
 144                         "failed\n");
 145                 goto err_out_cleanup_hw;
 146         }
 147 out:
 148         return err;
 149
 150 err_out_cleanup_hw:
 151         os_close_file(random_fd);
 152         random_fd = -1;
 153         goto out;
 154 }
 155
 156 /*
 157  * rng_cleanup - shutdown RNG module
 158  */
 159 static void __exit rng_cleanup (void)
 160 {
 161         os_close_file(random_fd);
 162         misc_deregister (&rng_miscdev);
 163 }
 164
 165 module_init (rng_init);
 166 module_exit (rng_cleanup);
 167
 168 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 169 MODULE_LICENSE("GPL");