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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 <asm/barrier.h>
8#include <linux/err.h>
9#include <linux/hw_random.h>
10#include <linux/scatterlist.h>
11#include <linux/spinlock.h>
12#include <linux/virtio.h>
13#include <linux/virtio_rng.h>
14#include <linux/module.h>
15#include <linux/slab.h>
16
17static DEFINE_IDA(rng_index_ida);
18
19struct virtrng_info {
20 struct hwrng hwrng;
21 struct virtqueue *vq;
22 char name[25];
23 int index;
24 bool hwrng_register_done;
25 bool hwrng_removed;
26 /* data transfer */
27 struct completion have_data;
28 unsigned int data_avail;
29 unsigned int data_idx;
30 /* minimal size returned by rng_buffer_size() */
31#if SMP_CACHE_BYTES < 32
32 u8 data[32];
33#else
34 u8 data[SMP_CACHE_BYTES];
35#endif
36};
37
38static void random_recv_done(struct virtqueue *vq)
39{
40 struct virtrng_info *vi = vq->vdev->priv;
41 unsigned int len;
42
43 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
44 if (!virtqueue_get_buf(vi->vq, &len))
45 return;
46
47 smp_store_release(&vi->data_avail, len);
48 complete(&vi->have_data);
49}
50
51static void request_entropy(struct virtrng_info *vi)
52{
53 struct scatterlist sg;
54
55 reinit_completion(&vi->have_data);
56 vi->data_idx = 0;
57
58 sg_init_one(&sg, vi->data, sizeof(vi->data));
59
60 /* There should always be room for one buffer. */
61 virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL);
62
63 virtqueue_kick(vi->vq);
64}
65
66static unsigned int copy_data(struct virtrng_info *vi, void *buf,
67 unsigned int size)
68{
69 size = min_t(unsigned int, size, vi->data_avail);
70 memcpy(buf, vi->data + vi->data_idx, size);
71 vi->data_idx += size;
72 vi->data_avail -= size;
73 if (vi->data_avail == 0)
74 request_entropy(vi);
75 return size;
76}
77
78static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
79{
80 int ret;
81 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
82 unsigned int chunk;
83 size_t read;
84
85 if (vi->hwrng_removed)
86 return -ENODEV;
87
88 read = 0;
89
90 /* copy available data */
91 if (smp_load_acquire(&vi->data_avail)) {
92 chunk = copy_data(vi, buf, size);
93 size -= chunk;
94 read += chunk;
95 }
96
97 if (!wait)
98 return read;
99
100 /* We have already copied available entropy,
101 * so either size is 0 or data_avail is 0
102 */
103 while (size != 0) {
104 /* data_avail is 0 but a request is pending */
105 ret = wait_for_completion_killable(&vi->have_data);
106 if (ret < 0)
107 return ret;
108 /* if vi->data_avail is 0, we have been interrupted
109 * by a cleanup, but buffer stays in the queue
110 */
111 if (vi->data_avail == 0)
112 return read;
113
114 chunk = copy_data(vi, buf + read, size);
115 size -= chunk;
116 read += chunk;
117 }
118
119 return read;
120}
121
122static void virtio_cleanup(struct hwrng *rng)
123{
124 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
125
126 complete(&vi->have_data);
127}
128
129static int probe_common(struct virtio_device *vdev)
130{
131 int err, index;
132 struct virtrng_info *vi = NULL;
133
134 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
135 if (!vi)
136 return -ENOMEM;
137
138 vi->index = index = ida_alloc(&rng_index_ida, GFP_KERNEL);
139 if (index < 0) {
140 err = index;
141 goto err_ida;
142 }
143 sprintf(vi->name, "virtio_rng.%d", index);
144 init_completion(&vi->have_data);
145
146 vi->hwrng = (struct hwrng) {
147 .read = virtio_read,
148 .cleanup = virtio_cleanup,
149 .priv = (unsigned long)vi,
150 .name = vi->name,
151 };
152 vdev->priv = vi;
153
154 /* We expect a single virtqueue. */
155 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
156 if (IS_ERR(vi->vq)) {
157 err = PTR_ERR(vi->vq);
158 goto err_find;
159 }
160
161 virtio_device_ready(vdev);
162
163 /* we always have a pending entropy request */
164 request_entropy(vi);
165
166 return 0;
167
168err_find:
169 ida_free(&rng_index_ida, index);
170err_ida:
171 kfree(vi);
172 return err;
173}
174
175static void remove_common(struct virtio_device *vdev)
176{
177 struct virtrng_info *vi = vdev->priv;
178
179 vi->hwrng_removed = true;
180 vi->data_avail = 0;
181 vi->data_idx = 0;
182 complete(&vi->have_data);
183 if (vi->hwrng_register_done)
184 hwrng_unregister(&vi->hwrng);
185 virtio_reset_device(vdev);
186 vdev->config->del_vqs(vdev);
187 ida_free(&rng_index_ida, vi->index);
188 kfree(vi);
189}
190
191static int virtrng_probe(struct virtio_device *vdev)
192{
193 return probe_common(vdev);
194}
195
196static void virtrng_remove(struct virtio_device *vdev)
197{
198 remove_common(vdev);
199}
200
201static void virtrng_scan(struct virtio_device *vdev)
202{
203 struct virtrng_info *vi = vdev->priv;
204 int err;
205
206 err = hwrng_register(&vi->hwrng);
207 if (!err)
208 vi->hwrng_register_done = true;
209}
210
211static int virtrng_freeze(struct virtio_device *vdev)
212{
213 remove_common(vdev);
214 return 0;
215}
216
217static int virtrng_restore(struct virtio_device *vdev)
218{
219 int err;
220
221 err = probe_common(vdev);
222 if (!err) {
223 struct virtrng_info *vi = vdev->priv;
224
225 /*
226 * Set hwrng_removed to ensure that virtio_read()
227 * does not block waiting for data before the
228 * registration is complete.
229 */
230 vi->hwrng_removed = true;
231 err = hwrng_register(&vi->hwrng);
232 if (!err) {
233 vi->hwrng_register_done = true;
234 vi->hwrng_removed = false;
235 }
236 }
237
238 return err;
239}
240
241static const struct virtio_device_id id_table[] = {
242 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
243 { 0 },
244};
245
246static struct virtio_driver virtio_rng_driver = {
247 .driver.name = KBUILD_MODNAME,
248 .id_table = id_table,
249 .probe = virtrng_probe,
250 .remove = virtrng_remove,
251 .scan = virtrng_scan,
252 .freeze = pm_sleep_ptr(virtrng_freeze),
253 .restore = pm_sleep_ptr(virtrng_restore),
254};
255
256module_virtio_driver(virtio_rng_driver);
257MODULE_DEVICE_TABLE(virtio, id_table);
258MODULE_DESCRIPTION("Virtio random number driver");
259MODULE_LICENSE("GPL");