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/module.h>
11#include <linux/fs.h>
12#include <linux/interrupt.h>
13#include <linux/miscdevice.h>
14#include <linux/delay.h>
15#include <asm/uaccess.h>
16#include <irq_kern.h>
17#include <os.h>
18
19/*
20 * core module and version information
21 */
22#define RNG_VERSION "1.0.0"
23#define RNG_MODULE_NAME "hw_random"
24
25#define RNG_MISCDEV_MINOR		183 /* official */
26
27/* Changed at init time, in the non-modular case, and at module load
28 * time, in the module case.  Presumably, the module subsystem
29 * protects against a module being loaded twice at the same time.
30 */
31static int random_fd = -1;
32static DECLARE_WAIT_QUEUE_HEAD(host_read_wait);
33
34static int rng_dev_open (struct inode *inode, struct file *filp)
35{
36	/* enforce read-only access to this chrdev */
37	if ((filp->f_mode & FMODE_READ) == 0)
38		return -EINVAL;
39	if ((filp->f_mode & FMODE_WRITE) != 0)
40		return -EINVAL;
41
42	return 0;
43}
44
45static atomic_t host_sleep_count = ATOMIC_INIT(0);
46
47static ssize_t rng_dev_read (struct file *filp, char __user *buf, size_t size,
48			     loff_t *offp)
49{
50	u32 data;
51	int n, ret = 0, have_data;
52
53	while (size) {
54		n = os_read_file(random_fd, &data, sizeof(data));
55		if (n > 0) {
56			have_data = n;
57			while (have_data && size) {
58				if (put_user((u8) data, buf++)) {
59					ret = ret ? : -EFAULT;
60					break;
61				}
62				size--;
63				ret++;
64				have_data--;
65				data >>= 8;
66			}
67		}
68		else if (n == -EAGAIN) {
69			DECLARE_WAITQUEUE(wait, current);
70
71			if (filp->f_flags & O_NONBLOCK)
72				return ret ? : -EAGAIN;
73
74			atomic_inc(&host_sleep_count);
75			reactivate_fd(random_fd, RANDOM_IRQ);
76			add_sigio_fd(random_fd);
77
78			add_wait_queue(&host_read_wait, &wait);
79			set_task_state(current, 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
98static 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 */
106static struct miscdevice rng_miscdev = {
107	RNG_MISCDEV_MINOR,
108	RNG_MODULE_NAME,
109	&rng_chrdev_ops,
110};
111
112static 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 */
122static 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	}
145out:
146	return err;
147
148err_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 */
157static void __exit rng_cleanup (void)
158{
159	os_close_file(random_fd);
160	misc_deregister (&rng_miscdev);
161}
162
163module_init (rng_init);
164module_exit (rng_cleanup);
165
166MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
167MODULE_LICENSE("GPL");
168