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