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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// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Randomness driver for virtio
4 * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
5 */
6
7#include <linux/err.h>
8#include <linux/hw_random.h>
9#include <linux/scatterlist.h>
10#include <linux/spinlock.h>
11#include <linux/virtio.h>
12#include <linux/virtio_rng.h>
13#include <linux/module.h>
14
15static DEFINE_IDA(rng_index_ida);
16
17struct virtrng_info {
18 struct hwrng hwrng;
19 struct virtqueue *vq;
20 struct completion have_data;
21 char name[25];
22 unsigned int data_avail;
23 int index;
24 bool busy;
25 bool hwrng_register_done;
26 bool hwrng_removed;
27};
28
29static void random_recv_done(struct virtqueue *vq)
30{
31 struct virtrng_info *vi = vq->vdev->priv;
32
33 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
34 if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
35 return;
36
37 complete(&vi->have_data);
38}
39
40/* The host will fill any buffer we give it with sweet, sweet randomness. */
41static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size)
42{
43 struct scatterlist sg;
44
45 sg_init_one(&sg, buf, size);
46
47 /* There should always be room for one buffer. */
48 virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL);
49
50 virtqueue_kick(vi->vq);
51}
52
53static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
54{
55 int ret;
56 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
57
58 if (vi->hwrng_removed)
59 return -ENODEV;
60
61 if (!vi->busy) {
62 vi->busy = true;
63 reinit_completion(&vi->have_data);
64 register_buffer(vi, buf, size);
65 }
66
67 if (!wait)
68 return 0;
69
70 ret = wait_for_completion_killable(&vi->have_data);
71 if (ret < 0)
72 return ret;
73
74 vi->busy = false;
75
76 return vi->data_avail;
77}
78
79static void virtio_cleanup(struct hwrng *rng)
80{
81 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
82
83 if (vi->busy)
84 wait_for_completion(&vi->have_data);
85}
86
87static int probe_common(struct virtio_device *vdev)
88{
89 int err, index;
90 struct virtrng_info *vi = NULL;
91
92 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
93 if (!vi)
94 return -ENOMEM;
95
96 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
97 if (index < 0) {
98 err = index;
99 goto err_ida;
100 }
101 sprintf(vi->name, "virtio_rng.%d", index);
102 init_completion(&vi->have_data);
103
104 vi->hwrng = (struct hwrng) {
105 .read = virtio_read,
106 .cleanup = virtio_cleanup,
107 .priv = (unsigned long)vi,
108 .name = vi->name,
109 .quality = 1000,
110 };
111 vdev->priv = vi;
112
113 /* We expect a single virtqueue. */
114 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
115 if (IS_ERR(vi->vq)) {
116 err = PTR_ERR(vi->vq);
117 goto err_find;
118 }
119
120 return 0;
121
122err_find:
123 ida_simple_remove(&rng_index_ida, index);
124err_ida:
125 kfree(vi);
126 return err;
127}
128
129static void remove_common(struct virtio_device *vdev)
130{
131 struct virtrng_info *vi = vdev->priv;
132
133 vi->hwrng_removed = true;
134 vi->data_avail = 0;
135 complete(&vi->have_data);
136 vdev->config->reset(vdev);
137 vi->busy = false;
138 if (vi->hwrng_register_done)
139 hwrng_unregister(&vi->hwrng);
140 vdev->config->del_vqs(vdev);
141 ida_simple_remove(&rng_index_ida, vi->index);
142 kfree(vi);
143}
144
145static int virtrng_probe(struct virtio_device *vdev)
146{
147 return probe_common(vdev);
148}
149
150static void virtrng_remove(struct virtio_device *vdev)
151{
152 remove_common(vdev);
153}
154
155static void virtrng_scan(struct virtio_device *vdev)
156{
157 struct virtrng_info *vi = vdev->priv;
158 int err;
159
160 err = hwrng_register(&vi->hwrng);
161 if (!err)
162 vi->hwrng_register_done = true;
163}
164
165#ifdef CONFIG_PM_SLEEP
166static int virtrng_freeze(struct virtio_device *vdev)
167{
168 remove_common(vdev);
169 return 0;
170}
171
172static int virtrng_restore(struct virtio_device *vdev)
173{
174 int err;
175
176 err = probe_common(vdev);
177 if (!err) {
178 struct virtrng_info *vi = vdev->priv;
179
180 /*
181 * Set hwrng_removed to ensure that virtio_read()
182 * does not block waiting for data before the
183 * registration is complete.
184 */
185 vi->hwrng_removed = true;
186 err = hwrng_register(&vi->hwrng);
187 if (!err) {
188 vi->hwrng_register_done = true;
189 vi->hwrng_removed = false;
190 }
191 }
192
193 return err;
194}
195#endif
196
197static struct virtio_device_id id_table[] = {
198 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
199 { 0 },
200};
201
202static struct virtio_driver virtio_rng_driver = {
203 .driver.name = KBUILD_MODNAME,
204 .driver.owner = THIS_MODULE,
205 .id_table = id_table,
206 .probe = virtrng_probe,
207 .remove = virtrng_remove,
208 .scan = virtrng_scan,
209#ifdef CONFIG_PM_SLEEP
210 .freeze = virtrng_freeze,
211 .restore = virtrng_restore,
212#endif
213};
214
215module_virtio_driver(virtio_rng_driver);
216MODULE_DEVICE_TABLE(virtio, id_table);
217MODULE_DESCRIPTION("Virtio random number driver");
218MODULE_LICENSE("GPL");