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/sched.h>
   9 #include <linux/module.h>
  10 #include <linux/fs.h>
  11 #include <linux/miscdevice.h>
  12 #include <linux/delay.h>
  13 #include <asm/uaccess.h>
  14 #include "os.h"
  15
  16 /*
  17  * core module and version information
  18  */
  19 #define RNG_VERSION "1.0.0"
  20 #define RNG_MODULE_NAME "random"
  21
  22 #define RNG_MISCDEV_MINOR               183 /* official */
  23
  24 /* Changed at init time, in the non-modular case, and at module load
  25  * time, in the module case.  Presumably, the module subsystem
  26  * protects against a module being loaded twice at the same time.
  27  */
  28 static int random_fd = -1;
  29
  30 static int rng_dev_open (struct inode *inode, struct file *filp)
  31 {
  32         /* enforce read-only access to this chrdev */
  33         if ((filp->f_mode & FMODE_READ) == 0)
  34                 return -EINVAL;
  35         if (filp->f_mode & FMODE_WRITE)
  36                 return -EINVAL;
  37
  38         return 0;
  39 }
  40
  41 static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
  42                              loff_t * offp)
  43 {
  44         u32 data;
  45         int n, ret = 0, have_data;
  46
  47         while(size){
  48                 n = os_read_file(random_fd, &data, sizeof(data));
  49                 if(n > 0){
  50                         have_data = n;
  51                         while (have_data && size) {
  52                                 if (put_user((u8)data, buf++)) {
  53                                         ret = ret ? : -EFAULT;
  54                                         break;
  55                                 }
  56                                 size--;
  57                                 ret++;
  58                                 have_data--;
  59                                 data>>=8;
  60                         }
  61                 }
  62                 else if(n == -EAGAIN){
  63                         if (filp->f_flags & O_NONBLOCK)
  64                                 return ret ? : -EAGAIN;
  65
  66                         if(need_resched())
  67                                 schedule_timeout_interruptible(1);
  68                 }
  69                 else return n;
  70                 if (signal_pending (current))
  71                         return ret ? : -ERESTARTSYS;
  72         }
  73         return ret;
  74 }
  75
  76 static const struct file_operations rng_chrdev_ops = {
  77         .owner          = THIS_MODULE,
  78         .open           = rng_dev_open,
  79         .read           = rng_dev_read,
  80 };
  81
  82 /* rng_init shouldn't be called more than once at boot time */
  83 static struct miscdevice rng_miscdev = {
  84         RNG_MISCDEV_MINOR,
  85         RNG_MODULE_NAME,
  86         &rng_chrdev_ops,
  87 };
  88
  89 /*
  90  * rng_init - initialize RNG module
  91  */
  92 static int __init rng_init (void)
  93 {
  94         int err;
  95
  96         err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
  97         if(err < 0)
  98                 goto out;
  99
 100         random_fd = err;
 101
 102         err = os_set_fd_block(random_fd, 0);
 103         if(err)
 104                 goto err_out_cleanup_hw;
 105
 106         err = misc_register (&rng_miscdev);
 107         if (err) {
 108                 printk (KERN_ERR RNG_MODULE_NAME ": misc device register failed\n");
 109                 goto err_out_cleanup_hw;
 110         }
 111
 112  out:
 113         return err;
 114
 115  err_out_cleanup_hw:
 116         random_fd = -1;
 117         goto out;
 118 }
 119
 120 /*
 121  * rng_cleanup - shutdown RNG module
 122  */
 123 static void __exit rng_cleanup (void)
 124 {
 125         misc_deregister (&rng_miscdev);
 126 }
 127
 128 module_init (rng_init);
 129 module_exit (rng_cleanup);
 130
 131 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 132 MODULE_LICENSE("GPL");