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 /* Changed at init time, in the non-modular case, and at module load
  24  * time, in the module case.  Presumably, the module subsystem
  25  * protects against a module being loaded twice at the same time.
  26  */
  27 static int random_fd = -1;
  28
  29 static int rng_dev_open (struct inode *inode, struct file *filp)
  30 {
  31         /* enforce read-only access to this chrdev */
  32         if ((filp->f_mode & FMODE_READ) == 0)
  33                 return -EINVAL;
  34         if (filp->f_mode & FMODE_WRITE)
  35                 return -EINVAL;
  36
  37         return 0;
  38 }
  39
  40 static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
  41                              loff_t * offp)
  42 {
  43         u32 data;
  44         int n, ret = 0, have_data;
  45
  46         while(size){
  47                 n = os_read_file(random_fd, &data, sizeof(data));
  48                 if(n > 0){
  49                         have_data = n;
  50                         while (have_data && size) {
  51                                 if (put_user((u8)data, buf++)) {
  52                                         ret = ret ? : -EFAULT;
  53                                         break;
  54                                 }
  55                                 size--;
  56                                 ret++;
  57                                 have_data--;
  58                                 data>>=8;
  59                         }
  60                 }
  61                 else if(n == -EAGAIN){
  62                         if (filp->f_flags & O_NONBLOCK)
  63                                 return ret ? : -EAGAIN;
  64
  65                         if(need_resched())
  66                                 schedule_timeout_interruptible(1);
  67                 }
  68                 else return n;
  69                 if (signal_pending (current))
  70                         return ret ? : -ERESTARTSYS;
  71         }
  72         return ret;
  73 }
  74
  75 static const struct file_operations rng_chrdev_ops = {
  76         .owner          = THIS_MODULE,
  77         .open           = rng_dev_open,
  78         .read           = rng_dev_read,
  79 };
  80
  81 /* rng_init shouldn't be called more than once at boot time */
  82 static struct miscdevice rng_miscdev = {
  83         RNG_MISCDEV_MINOR,
  84         RNG_MODULE_NAME,
  85         &rng_chrdev_ops,
  86 };
  87
  88 /*
  89  * rng_init - initialize RNG module
  90  */
  91 static int __init rng_init (void)
  92 {
  93         int err;
  94
  95         err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
  96         if(err < 0)
  97                 goto out;
  98
  99         random_fd = err;
 100
 101         err = os_set_fd_block(random_fd, 0);
 102         if(err)
 103                 goto err_out_cleanup_hw;
 104
 105         err = misc_register (&rng_miscdev);
 106         if (err) {
 107                 printk (KERN_ERR RNG_MODULE_NAME ": misc device register failed\n");
 108                 goto err_out_cleanup_hw;
 109         }
 110
 111  out:
 112         return err;
 113
 114  err_out_cleanup_hw:
 115         random_fd = -1;
 116         goto out;
 117 }
 118
 119 /*
 120  * rng_cleanup - shutdown RNG module
 121  */
 122 static void __exit rng_cleanup (void)
 123 {
 124         misc_deregister (&rng_miscdev);
 125 }
 126
 127 module_init (rng_init);
 128 module_exit (rng_cleanup);
 129
 130 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 131 MODULE_LICENSE("GPL");