tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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};
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->busy) {
72 vi->busy = true;
73 init_completion(&vi->have_data);
74 register_buffer(vi, buf, size);
75 }
76
77 if (!wait)
78 return 0;
79
80 ret = wait_for_completion_killable(&vi->have_data);
81 if (ret < 0)
82 return ret;
83
84 vi->busy = false;
85
86 return vi->data_avail;
87}
88
89static void virtio_cleanup(struct hwrng *rng)
90{
91 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
92
93 if (vi->busy)
94 wait_for_completion(&vi->have_data);
95}
96
97static int probe_common(struct virtio_device *vdev)
98{
99 int err, index;
100 struct virtrng_info *vi = NULL;
101
102 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
103 if (!vi)
104 return -ENOMEM;
105
106 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
107 if (index < 0) {
108 kfree(vi);
109 return index;
110 }
111 sprintf(vi->name, "virtio_rng.%d", index);
112 init_completion(&vi->have_data);
113
114 vi->hwrng = (struct hwrng) {
115 .read = virtio_read,
116 .cleanup = virtio_cleanup,
117 .priv = (unsigned long)vi,
118 .name = vi->name,
119 .quality = 1000,
120 };
121 vdev->priv = vi;
122
123 /* We expect a single virtqueue. */
124 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
125 if (IS_ERR(vi->vq)) {
126 err = PTR_ERR(vi->vq);
127 vi->vq = NULL;
128 kfree(vi);
129 ida_simple_remove(&rng_index_ida, index);
130 return err;
131 }
132
133 return 0;
134}
135
136static void remove_common(struct virtio_device *vdev)
137{
138 struct virtrng_info *vi = vdev->priv;
139
140 vdev->config->reset(vdev);
141 vi->busy = false;
142 if (vi->hwrng_register_done)
143 hwrng_unregister(&vi->hwrng);
144 vdev->config->del_vqs(vdev);
145 ida_simple_remove(&rng_index_ida, vi->index);
146 kfree(vi);
147}
148
149static int virtrng_probe(struct virtio_device *vdev)
150{
151 return probe_common(vdev);
152}
153
154static void virtrng_remove(struct virtio_device *vdev)
155{
156 remove_common(vdev);
157}
158
159static void virtrng_scan(struct virtio_device *vdev)
160{
161 struct virtrng_info *vi = vdev->priv;
162 int err;
163
164 err = hwrng_register(&vi->hwrng);
165 if (!err)
166 vi->hwrng_register_done = true;
167}
168
169#ifdef CONFIG_PM_SLEEP
170static int virtrng_freeze(struct virtio_device *vdev)
171{
172 remove_common(vdev);
173 return 0;
174}
175
176static int virtrng_restore(struct virtio_device *vdev)
177{
178 return probe_common(vdev);
179}
180#endif
181
182static struct virtio_device_id id_table[] = {
183 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
184 { 0 },
185};
186
187static struct virtio_driver virtio_rng_driver = {
188 .driver.name = KBUILD_MODNAME,
189 .driver.owner = THIS_MODULE,
190 .id_table = id_table,
191 .probe = virtrng_probe,
192 .remove = virtrng_remove,
193 .scan = virtrng_scan,
194#ifdef CONFIG_PM_SLEEP
195 .freeze = virtrng_freeze,
196 .restore = virtrng_restore,
197#endif
198};
199
200module_virtio_driver(virtio_rng_driver);
201MODULE_DEVICE_TABLE(virtio, id_table);
202MODULE_DESCRIPTION("Virtio random number driver");
203MODULE_LICENSE("GPL");