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/signal.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 <linux/uaccess.h>
  16 #include <init.h>
  17 #include <irq_kern.h>
  18 #include <os.h>
  19
  20 /*
  21  * core module and version information
  22  */
  23 #define RNG_VERSION "1.0.0"
  24 #define RNG_MODULE_NAME "hw_random"
  25
  26 #define RNG_MISCDEV_MINOR               183 /* official */
  27
  28 /* Changed at init time, in the non-modular case, and at module load
  29  * time, in the module case.  Presumably, the module subsystem
  30  * protects against a module being loaded twice at the same time.
  31  */
  32 static int random_fd = -1;
  33 static DECLARE_WAIT_QUEUE_HEAD(host_read_wait);
  34
  35 static int rng_dev_open (struct inode *inode, struct file *filp)
  36 {
  37         /* enforce read-only access to this chrdev */
  38         if ((filp->f_mode & FMODE_READ) == 0)
  39                 return -EINVAL;
  40         if ((filp->f_mode & FMODE_WRITE) != 0)
  41                 return -EINVAL;
  42
  43         return 0;
  44 }
  45
  46 static atomic_t host_sleep_count = ATOMIC_INIT(0);
  47
  48 static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
  49                              loff_t *offp)
  50 {
  51         u32 data;
  52         int n, ret = 0, have_data;
  53
  54         while (size) {
  55                 n = os_read_file(random_fd, &data, sizeof(data));
  56                 if (n > 0) {
  57                         have_data = n;
  58                         while (have_data && size) {
  59                                 if (put_user((u8) data, buf++)) {
  60                                         ret = ret ? : -EFAULT;
  61                                         break;
  62                                 }
  63                                 size--;
  64                                 ret++;
  65                                 have_data--;
  66                                 data >>= 8;
  67                         }
  68                 }
  69                 else if (n == -EAGAIN) {
  70                         DECLARE_WAITQUEUE(wait, current);
  71
  72                         if (filp->f_flags & O_NONBLOCK)
  73                                 return ret ? : -EAGAIN;
  74
  75                         atomic_inc(&host_sleep_count);
  76                         add_sigio_fd(random_fd);
  77
  78                         add_wait_queue(&host_read_wait, &wait);
  79                         set_current_state(TASK_INTERRUPTIBLE);
  80
  81                         schedule();
  82                         remove_wait_queue(&host_read_wait, &wait);
  83
  84                         if (atomic_dec_and_test(&host_sleep_count)) {
  85                                 ignore_sigio_fd(random_fd);
  86                                 deactivate_fd(random_fd, RANDOM_IRQ);
  87                         }
  88                 }
  89                 else
  90                         return n;
  91
  92                 if (signal_pending (current))
  93                         return ret ? : -ERESTARTSYS;
  94         }
  95         return ret;
  96 }
  97
  98 static const struct file_operations rng_chrdev_ops = {
  99         .owner          = THIS_MODULE,
 100         .open           = rng_dev_open,
 101         .read           = rng_dev_read,
 102         .llseek         = noop_llseek,
 103 };
 104
 105 /* rng_init shouldn't be called more than once at boot time */
 106 static struct miscdevice rng_miscdev = {
 107         RNG_MISCDEV_MINOR,
 108         RNG_MODULE_NAME,
 109         &rng_chrdev_ops,
 110 };
 111
 112 static irqreturn_t random_interrupt(int irq, void *data)
 113 {
 114         wake_up(&host_read_wait);
 115
 116         return IRQ_HANDLED;
 117 }
 118
 119 /*
 120  * rng_init - initialize RNG module
 121  */
 122 static int __init rng_init (void)
 123 {
 124         int err;
 125
 126         err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
 127         if (err < 0)
 128                 goto out;
 129
 130         random_fd = err;
 131
 132         err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt,
 133                              0, "random", NULL);
 134         if (err)
 135                 goto err_out_cleanup_hw;
 136
 137         sigio_broken(random_fd, 1);
 138
 139         err = misc_register (&rng_miscdev);
 140         if (err) {
 141                 printk (KERN_ERR RNG_MODULE_NAME ": misc device register "
 142                         "failed\n");
 143                 goto err_out_cleanup_hw;
 144         }
 145 out:
 146         return err;
 147
 148 err_out_cleanup_hw:
 149         os_close_file(random_fd);
 150         random_fd = -1;
 151         goto out;
 152 }
 153
 154 /*
 155  * rng_cleanup - shutdown RNG module
 156  */
 157
 158 static void cleanup(void)
 159 {
 160         free_irq_by_fd(random_fd);
 161         os_close_file(random_fd);
 162 }
 163
 164 static void __exit rng_cleanup(void)
 165 {
 166         os_close_file(random_fd);
 167         misc_deregister (&rng_miscdev);
 168 }
 169
 170 module_init (rng_init);
 171 module_exit (rng_cleanup);
 172 __uml_exitcall(cleanup);
 173
 174 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 175 MODULE_LICENSE("GPL");