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/hw_random.h>
  15 #include <linux/delay.h>
  16 #include <linux/uaccess.h>
  17 #include <init.h>
  18 #include <irq_kern.h>
  19 #include <os.h>
  20
  21 /*
  22  * core module information
  23  */
  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 struct hwrng hwrng = { 0, };
  32 static DECLARE_COMPLETION(have_data);
  33
  34 static int rng_dev_read(struct hwrng *rng, void *buf, size_t max, bool block)
  35 {
  36         int ret;
  37
  38         for (;;) {
  39                 ret = os_read_file(random_fd, buf, max);
  40                 if (block && ret == -EAGAIN) {
  41                         add_sigio_fd(random_fd);
  42
  43                         ret = wait_for_completion_killable(&have_data);
  44
  45                         ignore_sigio_fd(random_fd);
  46                         deactivate_fd(random_fd, RANDOM_IRQ);
  47
  48                         if (ret < 0)
  49                                 break;
  50                 } else {
  51                         break;
  52                 }
  53         }
  54
  55         return ret != -EAGAIN ? ret : 0;
  56 }
  57
  58 static irqreturn_t random_interrupt(int irq, void *data)
  59 {
  60         complete(&have_data);
  61
  62         return IRQ_HANDLED;
  63 }
  64
  65 /*
  66  * rng_init - initialize RNG module
  67  */
  68 static int __init rng_init (void)
  69 {
  70         int err;
  71
  72         err = os_open_file("/dev/random", of_read(OPENFLAGS()), 0);
  73         if (err < 0)
  74                 goto out;
  75
  76         random_fd = err;
  77         err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt,
  78                              0, "random", NULL);
  79         if (err < 0)
  80                 goto err_out_cleanup_hw;
  81
  82         sigio_broken(random_fd);
  83         hwrng.name = RNG_MODULE_NAME;
  84         hwrng.read = rng_dev_read;
  85         hwrng.quality = 1024;
  86
  87         err = hwrng_register(&hwrng);
  88         if (err) {
  89                 pr_err(RNG_MODULE_NAME " registering failed (%d)\n", err);
  90                 goto err_out_cleanup_hw;
  91         }
  92 out:
  93         return err;
  94
  95 err_out_cleanup_hw:
  96         os_close_file(random_fd);
  97         random_fd = -1;
  98         goto out;
  99 }
 100
 101 /*
 102  * rng_cleanup - shutdown RNG module
 103  */
 104
 105 static void cleanup(void)
 106 {
 107         free_irq_by_fd(random_fd);
 108         os_close_file(random_fd);
 109 }
 110
 111 static void __exit rng_cleanup(void)
 112 {
 113         hwrng_unregister(&hwrng);
 114         os_close_file(random_fd);
 115 }
 116
 117 module_init (rng_init);
 118 module_exit (rng_cleanup);
 119 __uml_exitcall(cleanup);
 120
 121 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 122 MODULE_LICENSE("GPL");