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
rng_dev_open(struct inode * inode,struct file * filp)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
rng_dev_read(struct file * filp,char __user * buf,size_t size,loff_t * offp)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
random_interrupt(int irq,void * data)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 */
rng_init(void)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
cleanup(void)156 static void cleanup(void)
157 {
158 free_irq_by_fd(random_fd);
159 os_close_file(random_fd);
160 }
161
rng_cleanup(void)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");
174