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.h>
  10 #include <linux/smp_lock.h>
  11 #include <linux/module.h>
  12 #include <linux/fs.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/miscdevice.h>
  15 #include <linux/delay.h>
  16 #include <asm/uaccess.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         cycle_kernel_lock();
  38
  39         /* enforce read-only access to this chrdev */
  40         if ((filp->f_mode & FMODE_READ) == 0)
  41                 return -EINVAL;
  42         if ((filp->f_mode & FMODE_WRITE) != 0)
  43                 return -EINVAL;
  44
  45         return 0;
  46 }
  47
  48 static atomic_t host_sleep_count = ATOMIC_INIT(0);
  49
  50 static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
  51                              loff_t *offp)
  52 {
  53         u32 data;
  54         int n, ret = 0, have_data;
  55
  56         while (size) {
  57                 n = os_read_file(random_fd, &data, sizeof(data));
  58                 if (n > 0) {
  59                         have_data = n;
  60                         while (have_data && size) {
  61                                 if (put_user((u8) data, buf++)) {
  62                                         ret = ret ? : -EFAULT;
  63                                         break;
  64                                 }
  65                                 size--;
  66                                 ret++;
  67                                 have_data--;
  68                                 data >>= 8;
  69                         }
  70                 }
  71                 else if (n == -EAGAIN) {
  72                         DECLARE_WAITQUEUE(wait, current);
  73
  74                         if (filp->f_flags & O_NONBLOCK)
  75                                 return ret ? : -EAGAIN;
  76
  77                         atomic_inc(&host_sleep_count);
  78                         reactivate_fd(random_fd, RANDOM_IRQ);
  79                         add_sigio_fd(random_fd);
  80
  81                         add_wait_queue(&host_read_wait, &wait);
  82                         set_task_state(current, TASK_INTERRUPTIBLE);
  83
  84                         schedule();
  85                         set_task_state(current, TASK_RUNNING);
  86                         remove_wait_queue(&host_read_wait, &wait);
  87
  88                         if (atomic_dec_and_test(&host_sleep_count)) {
  89                                 ignore_sigio_fd(random_fd);
  90                                 deactivate_fd(random_fd, RANDOM_IRQ);
  91                         }
  92                 }
  93                 else
  94                         return n;
  95
  96                 if (signal_pending (current))
  97                         return ret ? : -ERESTARTSYS;
  98         }
  99         return ret;
 100 }
 101
 102 static const struct file_operations rng_chrdev_ops = {
 103         .owner          = THIS_MODULE,
 104         .open           = rng_dev_open,
 105         .read           = rng_dev_read,
 106 };
 107
 108 /* rng_init shouldn't be called more than once at boot time */
 109 static struct miscdevice rng_miscdev = {
 110         RNG_MISCDEV_MINOR,
 111         RNG_MODULE_NAME,
 112         &rng_chrdev_ops,
 113 };
 114
 115 static irqreturn_t random_interrupt(int irq, void *data)
 116 {
 117         wake_up(&host_read_wait);
 118
 119         return IRQ_HANDLED;
 120 }
 121
 122 /*
 123  * rng_init - initialize RNG module
 124  */
 125 static int __init rng_init (void)
 126 {
 127         int err;
 128
 129         err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
 130         if (err < 0)
 131                 goto out;
 132
 133         random_fd = err;
 134
 135         err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt,
 136                              IRQF_DISABLED | IRQF_SAMPLE_RANDOM, "random",
 137                              NULL);
 138         if (err)
 139                 goto err_out_cleanup_hw;
 140
 141         sigio_broken(random_fd, 1);
 142
 143         err = misc_register (&rng_miscdev);
 144         if (err) {
 145                 printk (KERN_ERR RNG_MODULE_NAME ": misc device register "
 146                         "failed\n");
 147                 goto err_out_cleanup_hw;
 148         }
 149 out:
 150         return err;
 151
 152 err_out_cleanup_hw:
 153         os_close_file(random_fd);
 154         random_fd = -1;
 155         goto out;
 156 }
 157
 158 /*
 159  * rng_cleanup - shutdown RNG module
 160  */
 161 static void __exit rng_cleanup (void)
 162 {
 163         os_close_file(random_fd);
 164         misc_deregister (&rng_miscdev);
 165 }
 166
 167 module_init (rng_init);
 168 module_exit (rng_cleanup);
 169
 170 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 171 MODULE_LICENSE("GPL");