1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
/*
* Randomness driver for virtio
* Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/err.h>
#include <linux/hw_random.h>
#include <linux/scatterlist.h>
#include <linux/spinlock.h>
#include <linux/virtio.h>
#include <linux/virtio_rng.h>
/* The host will fill any buffer we give it with sweet, sweet randomness. We
* give it 64 bytes at a time, and the hwrng framework takes it 4 bytes at a
* time. */
#define RANDOM_DATA_SIZE 64
static struct virtqueue *vq;
static u32 *random_data;
static unsigned int data_left;
static DECLARE_COMPLETION(have_data);
static void random_recv_done(struct virtqueue *vq)
{
int len;
/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
if (!vq->vq_ops->get_buf(vq, &len))
return;
data_left = len / sizeof(random_data[0]);
complete(&have_data);
}
static void register_buffer(void)
{
struct scatterlist sg;
sg_init_one(&sg, random_data, RANDOM_DATA_SIZE);
/* There should always be room for one buffer. */
if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) != 0)
BUG();
vq->vq_ops->kick(vq);
}
/* At least we don't udelay() in a loop like some other drivers. */
static int virtio_data_present(struct hwrng *rng, int wait)
{
if (data_left)
return 1;
if (!wait)
return 0;
wait_for_completion(&have_data);
return 1;
}
/* virtio_data_present() must have succeeded before this is called. */
static int virtio_data_read(struct hwrng *rng, u32 *data)
{
BUG_ON(!data_left);
*data = random_data[--data_left];
if (!data_left) {
init_completion(&have_data);
register_buffer();
}
return sizeof(*data);
}
static struct hwrng virtio_hwrng = {
.name = "virtio",
.data_present = virtio_data_present,
.data_read = virtio_data_read,
};
static int virtrng_probe(struct virtio_device *vdev)
{
int err;
/* We expect a single virtqueue. */
vq = virtio_find_single_vq(vdev, random_recv_done, "input");
if (IS_ERR(vq))
return PTR_ERR(vq);
err = hwrng_register(&virtio_hwrng);
if (err) {
vdev->config->del_vqs(vdev);
return err;
}
register_buffer();
return 0;
}
static void virtrng_remove(struct virtio_device *vdev)
{
vdev->config->reset(vdev);
hwrng_unregister(&virtio_hwrng);
vdev->config->del_vqs(vdev);
}
static struct virtio_device_id id_table[] = {
{ VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
{ 0 },
};
static struct virtio_driver virtio_rng = {
.driver.name = KBUILD_MODNAME,
.driver.owner = THIS_MODULE,
.id_table = id_table,
.probe = virtrng_probe,
.remove = __devexit_p(virtrng_remove),
};
static int __init init(void)
{
int err;
random_data = kmalloc(RANDOM_DATA_SIZE, GFP_KERNEL);
if (!random_data)
return -ENOMEM;
err = register_virtio_driver(&virtio_rng);
if (err)
kfree(random_data);
return err;
}
static void __exit fini(void)
{
kfree(random_data);
unregister_virtio_driver(&virtio_rng);
}
module_init(init);
module_exit(fini);
MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio random number driver");
MODULE_LICENSE("GPL");
|
