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                                 current->state = TASK_INTERRUPTIBLE;
  63                                 schedule_timeout(1);
  64                         }
  65                 }
  66                 else return n;
  67                 if (signal_pending (current))
  68                         return ret ? : -ERESTARTSYS;
  69         }
  70         return ret;
  71 }
  72
  73 static struct file_operations rng_chrdev_ops = {
  74         .owner          = THIS_MODULE,
  75         .open           = rng_dev_open,
  76         .read           = rng_dev_read,
  77 };
  78
  79 static struct miscdevice rng_miscdev = {
  80         RNG_MISCDEV_MINOR,
  81         RNG_MODULE_NAME,
  82         &rng_chrdev_ops,
  83 };
  84
  85 /*
  86  * rng_init - initialize RNG module
  87  */
  88 static int __init rng_init (void)
  89 {
  90         int err;
  91
  92         err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
  93         if(err < 0)
  94                 goto out;
  95
  96         random_fd = err;
  97
  98         err = os_set_fd_block(random_fd, 0);
  99         if(err)
 100                 goto err_out_cleanup_hw;
 101
 102         err = misc_register (&rng_miscdev);
 103         if (err) {
 104                 printk (KERN_ERR RNG_MODULE_NAME ": misc device register failed\n");
 105                 goto err_out_cleanup_hw;
 106         }
 107
 108  out:
 109         return err;
 110
 111  err_out_cleanup_hw:
 112         random_fd = -1;
 113         goto out;
 114 }
 115
 116 /*
 117  * rng_cleanup - shutdown RNG module
 118  */
 119 static void __exit rng_cleanup (void)
 120 {
 121         misc_deregister (&rng_miscdev);
 122 }
 123
 124 module_init (rng_init);
 125 module_exit (rng_cleanup);
 126
 127 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 128 MODULE_LICENSE("GPL");