Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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 */
32static int random_fd = -1;
33static DECLARE_WAIT_QUEUE_HEAD(host_read_wait);
34
35static 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
48static atomic_t host_sleep_count = ATOMIC_INIT(0);
49
50static 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
102static 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 */
109static struct miscdevice rng_miscdev = {
110 RNG_MISCDEV_MINOR,
111 RNG_MODULE_NAME,
112 &rng_chrdev_ops,
113};
114
115static 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 */
125static 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 }
149out:
150 return err;
151
152err_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 */
161static void __exit rng_cleanup (void)
162{
163 os_close_file(random_fd);
164 misc_deregister (&rng_miscdev);
165}
166
167module_init (rng_init);
168module_exit (rng_cleanup);
169
170MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
171MODULE_LICENSE("GPL");