arch/um/drivers/random.c

   1 /* Copyright (C) 2005 Jeff Dike <jdike@addtoit.com> */
   2 /* Much of this ripped from drivers/char/hw_random.c, see there for other
   3  * copyright.
   4  *
   5  * This software may be used and distributed according to the terms
   6  * of the GNU General Public License, incorporated herein by reference.
   7  */
   8 #include <linux/module.h>
   9 #include <linux/fs.h>
  10 #include <linux/miscdevice.h>
  11 #include <linux/delay.h>
  12 #include <asm/uaccess.h>
  13 #include "os.h"
  14
  15 /*
  16  * core module and version information
  17  */
  18 #define RNG_VERSION "1.0.0"
  19 #define RNG_MODULE_NAME "random"
  20
  21 #define RNG_MISCDEV_MINOR               183 /* official */
  22
  23 static int random_fd = -1;
  24
  25 static int rng_dev_open (struct inode *inode, struct file *filp)
  26 {
  27         /* enforce read-only access to this chrdev */
  28         if ((filp->f_mode & FMODE_READ) == 0)
  29                 return -EINVAL;
  30         if (filp->f_mode & FMODE_WRITE)
  31                 return -EINVAL;
  32
  33         return 0;
  34 }
  35
  36 static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
  37                              loff_t * offp)
  38 {
  39         u32 data;
  40         int n, ret = 0, have_data;
  41
  42         while(size){
  43                 n = os_read_file(random_fd, &data, sizeof(data));
  44                 if(n > 0){
  45                         have_data = n;
  46                         while (have_data && size) {
  47                                 if (put_user((u8)data, buf++)) {
  48                                         ret = ret ? : -EFAULT;
  49                                         break;
  50                                 }
  51                                 size--;
  52                                 ret++;
  53                                 have_data--;
  54                                 data>>=8;
  55                         }
  56                 }
  57                 else if(n == -EAGAIN){
  58                         if (filp->f_flags & O_NONBLOCK)
  59                                 return ret ? : -EAGAIN;
  60
  61                         if(need_resched())
  62                                 schedule_timeout_interruptible(1);
  63                 }
  64                 else return n;
  65                 if (signal_pending (current))
  66                         return ret ? : -ERESTARTSYS;
  67         }
  68         return ret;
  69 }
  70
  71 static const struct file_operations rng_chrdev_ops = {
  72         .owner          = THIS_MODULE,
  73         .open           = rng_dev_open,
  74         .read           = rng_dev_read,
  75 };
  76
  77 static struct miscdevice rng_miscdev = {
  78         RNG_MISCDEV_MINOR,
  79         RNG_MODULE_NAME,
  80         &rng_chrdev_ops,
  81 };
  82
  83 /*
  84  * rng_init - initialize RNG module
  85  */
  86 static int __init rng_init (void)
  87 {
  88         int err;
  89
  90         err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
  91         if(err < 0)
  92                 goto out;
  93
  94         random_fd = err;
  95
  96         err = os_set_fd_block(random_fd, 0);
  97         if(err)
  98                 goto err_out_cleanup_hw;
  99
 100         err = misc_register (&rng_miscdev);
 101         if (err) {
 102                 printk (KERN_ERR RNG_MODULE_NAME ": misc device register failed\n");
 103                 goto err_out_cleanup_hw;
 104         }
 105
 106  out:
 107         return err;
 108
 109  err_out_cleanup_hw:
 110         random_fd = -1;
 111         goto out;
 112 }
 113
 114 /*
 115  * rng_cleanup - shutdown RNG module
 116  */
 117 static void __exit rng_cleanup (void)
 118 {
 119         misc_deregister (&rng_miscdev);
 120 }
 121
 122 module_init (rng_init);
 123 module_exit (rng_cleanup);
 124
 125 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 126 MODULE_LICENSE("GPL");