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1/*
2 * Randomness driver for virtio
3 * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18 */
19
20#include <linux/err.h>
21#include <linux/hw_random.h>
22#include <linux/scatterlist.h>
23#include <linux/spinlock.h>
24#include <linux/virtio.h>
25#include <linux/virtio_rng.h>
26
27static struct virtqueue *vq;
28static unsigned int data_avail;
29static DECLARE_COMPLETION(have_data);
30static bool busy;
31
32static void random_recv_done(struct virtqueue *vq)
33{
34 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
35 if (!virtqueue_get_buf(vq, &data_avail))
36 return;
37
38 complete(&have_data);
39}
40
41/* The host will fill any buffer we give it with sweet, sweet randomness. */
42static void register_buffer(u8 *buf, size_t size)
43{
44 struct scatterlist sg;
45
46 sg_init_one(&sg, buf, size);
47
48 /* There should always be room for one buffer. */
49 if (virtqueue_add_buf(vq, &sg, 0, 1, buf) < 0)
50 BUG();
51
52 virtqueue_kick(vq);
53}
54
55static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
56{
57
58 if (!busy) {
59 busy = true;
60 init_completion(&have_data);
61 register_buffer(buf, size);
62 }
63
64 if (!wait)
65 return 0;
66
67 wait_for_completion(&have_data);
68
69 busy = false;
70
71 return data_avail;
72}
73
74static void virtio_cleanup(struct hwrng *rng)
75{
76 if (busy)
77 wait_for_completion(&have_data);
78}
79
80
81static struct hwrng virtio_hwrng = {
82 .name = "virtio",
83 .cleanup = virtio_cleanup,
84 .read = virtio_read,
85};
86
87static int virtrng_probe(struct virtio_device *vdev)
88{
89 int err;
90
91 /* We expect a single virtqueue. */
92 vq = virtio_find_single_vq(vdev, random_recv_done, "input");
93 if (IS_ERR(vq))
94 return PTR_ERR(vq);
95
96 err = hwrng_register(&virtio_hwrng);
97 if (err) {
98 vdev->config->del_vqs(vdev);
99 return err;
100 }
101
102 return 0;
103}
104
105static void __devexit virtrng_remove(struct virtio_device *vdev)
106{
107 vdev->config->reset(vdev);
108 hwrng_unregister(&virtio_hwrng);
109 vdev->config->del_vqs(vdev);
110}
111
112static struct virtio_device_id id_table[] = {
113 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
114 { 0 },
115};
116
117static struct virtio_driver virtio_rng_driver = {
118 .driver.name = KBUILD_MODNAME,
119 .driver.owner = THIS_MODULE,
120 .id_table = id_table,
121 .probe = virtrng_probe,
122 .remove = __devexit_p(virtrng_remove),
123};
124
125static int __init init(void)
126{
127 return register_virtio_driver(&virtio_rng_driver);
128}
129
130static void __exit fini(void)
131{
132 unregister_virtio_driver(&virtio_rng_driver);
133}
134module_init(init);
135module_exit(fini);
136
137MODULE_DEVICE_TABLE(virtio, id_table);
138MODULE_DESCRIPTION("Virtio random number driver");
139MODULE_LICENSE("GPL");
1/*
2 * Randomness driver for virtio
3 * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18 */
19
20#include <linux/err.h>
21#include <linux/hw_random.h>
22#include <linux/scatterlist.h>
23#include <linux/spinlock.h>
24#include <linux/virtio.h>
25#include <linux/virtio_rng.h>
26#include <linux/module.h>
27
28static DEFINE_IDA(rng_index_ida);
29
30struct virtrng_info {
31 struct hwrng hwrng;
32 struct virtqueue *vq;
33 struct completion have_data;
34 char name[25];
35 unsigned int data_avail;
36 int index;
37 bool busy;
38 bool hwrng_register_done;
39 bool hwrng_removed;
40};
41
42static void random_recv_done(struct virtqueue *vq)
43{
44 struct virtrng_info *vi = vq->vdev->priv;
45
46 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
47 if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
48 return;
49
50 complete(&vi->have_data);
51}
52
53/* The host will fill any buffer we give it with sweet, sweet randomness. */
54static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size)
55{
56 struct scatterlist sg;
57
58 sg_init_one(&sg, buf, size);
59
60 /* There should always be room for one buffer. */
61 virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL);
62
63 virtqueue_kick(vi->vq);
64}
65
66static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
67{
68 int ret;
69 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
70
71 if (vi->hwrng_removed)
72 return -ENODEV;
73
74 if (!vi->busy) {
75 vi->busy = true;
76 init_completion(&vi->have_data);
77 register_buffer(vi, buf, size);
78 }
79
80 if (!wait)
81 return 0;
82
83 ret = wait_for_completion_killable(&vi->have_data);
84 if (ret < 0)
85 return ret;
86
87 vi->busy = false;
88
89 return vi->data_avail;
90}
91
92static void virtio_cleanup(struct hwrng *rng)
93{
94 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
95
96 if (vi->busy)
97 wait_for_completion(&vi->have_data);
98}
99
100static int probe_common(struct virtio_device *vdev)
101{
102 int err, index;
103 struct virtrng_info *vi = NULL;
104
105 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
106 if (!vi)
107 return -ENOMEM;
108
109 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
110 if (index < 0) {
111 err = index;
112 goto err_ida;
113 }
114 sprintf(vi->name, "virtio_rng.%d", index);
115 init_completion(&vi->have_data);
116
117 vi->hwrng = (struct hwrng) {
118 .read = virtio_read,
119 .cleanup = virtio_cleanup,
120 .priv = (unsigned long)vi,
121 .name = vi->name,
122 .quality = 1000,
123 };
124 vdev->priv = vi;
125
126 /* We expect a single virtqueue. */
127 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
128 if (IS_ERR(vi->vq)) {
129 err = PTR_ERR(vi->vq);
130 goto err_find;
131 }
132
133 return 0;
134
135err_find:
136 ida_simple_remove(&rng_index_ida, index);
137err_ida:
138 kfree(vi);
139 return err;
140}
141
142static void remove_common(struct virtio_device *vdev)
143{
144 struct virtrng_info *vi = vdev->priv;
145
146 vi->hwrng_removed = true;
147 vi->data_avail = 0;
148 complete(&vi->have_data);
149 vdev->config->reset(vdev);
150 vi->busy = false;
151 if (vi->hwrng_register_done)
152 hwrng_unregister(&vi->hwrng);
153 vdev->config->del_vqs(vdev);
154 ida_simple_remove(&rng_index_ida, vi->index);
155 kfree(vi);
156}
157
158static int virtrng_probe(struct virtio_device *vdev)
159{
160 return probe_common(vdev);
161}
162
163static void virtrng_remove(struct virtio_device *vdev)
164{
165 remove_common(vdev);
166}
167
168static void virtrng_scan(struct virtio_device *vdev)
169{
170 struct virtrng_info *vi = vdev->priv;
171 int err;
172
173 err = hwrng_register(&vi->hwrng);
174 if (!err)
175 vi->hwrng_register_done = true;
176}
177
178#ifdef CONFIG_PM_SLEEP
179static int virtrng_freeze(struct virtio_device *vdev)
180{
181 remove_common(vdev);
182 return 0;
183}
184
185static int virtrng_restore(struct virtio_device *vdev)
186{
187 return probe_common(vdev);
188}
189#endif
190
191static struct virtio_device_id id_table[] = {
192 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
193 { 0 },
194};
195
196static struct virtio_driver virtio_rng_driver = {
197 .driver.name = KBUILD_MODNAME,
198 .driver.owner = THIS_MODULE,
199 .id_table = id_table,
200 .probe = virtrng_probe,
201 .remove = virtrng_remove,
202 .scan = virtrng_scan,
203#ifdef CONFIG_PM_SLEEP
204 .freeze = virtrng_freeze,
205 .restore = virtrng_restore,
206#endif
207};
208
209module_virtio_driver(virtio_rng_driver);
210MODULE_DEVICE_TABLE(virtio, id_table);
211MODULE_DESCRIPTION("Virtio random number driver");
212MODULE_LICENSE("GPL");