1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2013, Bryan Venteicher <bryanv@FreeBSD.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice unmodified, this list of conditions, and the following
12 * disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * $FreeBSD: head/sys/dev/virtio/random/virtio_random.c 338324 2018-08-26 12:51:46Z markm $
29 */
30
31 /* Driver for VirtIO entropy device. */
32
33 #include <sys/param.h>
34 #include <sys/kernel.h>
35 #include <sys/module.h>
36 #include <sys/thread.h>
37 #include <sys/sglist.h>
38 #include <sys/callout.h>
39 #include <sys/random.h>
40 #include <sys/systm.h>
41 #include <sys/bus.h>
42
43 #include <dev/virtual/virtio/virtio/virtio.h>
44 #include <dev/virtual/virtio/virtio/virtqueue.h>
45
46 struct vtrnd_softc {
47 device_t vtrnd_dev;
48 uint64_t vtrnd_features;
49 struct callout vtrnd_callout;
50 struct virtqueue *vtrnd_vq;
51 };
52
53 static int vtrnd_modevent(module_t, int, void *);
54
55 static int vtrnd_probe(device_t);
56 static int vtrnd_attach(device_t);
57 static int vtrnd_detach(device_t);
58
59 static void vtrnd_negotiate_features(struct vtrnd_softc *);
60 static int vtrnd_alloc_virtqueue(struct vtrnd_softc *);
61 static void vtrnd_harvest(struct vtrnd_softc *);
62 static void vtrnd_timer(void *);
63
64 #define VTRND_FEATURES 0
65
66 static struct virtio_feature_desc vtrnd_feature_desc[] = {
67 { 0, NULL }
68 };
69
70 static device_method_t vtrnd_methods[] = {
71 /* Device methods. */
72 DEVMETHOD(device_probe, vtrnd_probe),
73 DEVMETHOD(device_attach, vtrnd_attach),
74 DEVMETHOD(device_detach, vtrnd_detach),
75
76 DEVMETHOD_END
77 };
78
79 static driver_t vtrnd_driver = {
80 "vtrnd",
81 vtrnd_methods,
82 sizeof(struct vtrnd_softc)
83 };
84 static devclass_t vtrnd_devclass;
85
86 DRIVER_MODULE(virtio_random, virtio_pci, vtrnd_driver, vtrnd_devclass,
87 vtrnd_modevent, NULL);
88 MODULE_VERSION(virtio_random, 1);
89 MODULE_DEPEND(virtio_random, virtio, 1, 1, 1);
90
91 static int
vtrnd_modevent(module_t mod,int type,void * unused)92 vtrnd_modevent(module_t mod, int type, void *unused)
93 {
94 int error;
95
96 switch (type) {
97 case MOD_LOAD:
98 case MOD_UNLOAD:
99 case MOD_SHUTDOWN:
100 error = 0;
101 break;
102 default:
103 error = EOPNOTSUPP;
104 break;
105 }
106
107 return (error);
108 }
109
110 static int
vtrnd_probe(device_t dev)111 vtrnd_probe(device_t dev)
112 {
113
114 if (virtio_get_device_type(dev) != VIRTIO_ID_ENTROPY)
115 return (ENXIO);
116
117 device_set_desc(dev, "VirtIO Entropy Adapter");
118
119 return (BUS_PROBE_DEFAULT);
120 }
121
122 static int
vtrnd_attach(device_t dev)123 vtrnd_attach(device_t dev)
124 {
125 struct vtrnd_softc *sc;
126 int error;
127
128 sc = device_get_softc(dev);
129 sc->vtrnd_dev = dev;
130
131 callout_init_mp(&sc->vtrnd_callout);
132
133 virtio_set_feature_desc(dev, vtrnd_feature_desc);
134 vtrnd_negotiate_features(sc);
135
136 error = vtrnd_alloc_virtqueue(sc);
137 if (error) {
138 device_printf(dev, "cannot allocate virtqueue\n");
139 goto fail;
140 }
141
142 callout_reset(&sc->vtrnd_callout, 5 * hz, vtrnd_timer, sc);
143
144 fail:
145 if (error)
146 vtrnd_detach(dev);
147
148 return (error);
149 }
150
151 static int
vtrnd_detach(device_t dev)152 vtrnd_detach(device_t dev)
153 {
154 struct vtrnd_softc *sc;
155
156 sc = device_get_softc(dev);
157
158 callout_terminate(&sc->vtrnd_callout);
159
160 return (0);
161 }
162
163 static void
vtrnd_negotiate_features(struct vtrnd_softc * sc)164 vtrnd_negotiate_features(struct vtrnd_softc *sc)
165 {
166 device_t dev;
167 uint64_t features;
168
169 dev = sc->vtrnd_dev;
170 features = VTRND_FEATURES;
171
172 sc->vtrnd_features = virtio_negotiate_features(dev, features);
173 }
174
175 static int
vtrnd_alloc_virtqueue(struct vtrnd_softc * sc)176 vtrnd_alloc_virtqueue(struct vtrnd_softc *sc)
177 {
178 device_t dev;
179 struct vq_alloc_info vq_info;
180
181 dev = sc->vtrnd_dev;
182
183 VQ_ALLOC_INFO_INIT(&vq_info, 0, &sc->vtrnd_vq,
184 "%s request", device_get_nameunit(dev));
185
186 return (virtio_alloc_virtqueues(dev, 1, &vq_info));
187 }
188
189 static void
vtrnd_harvest(struct vtrnd_softc * sc)190 vtrnd_harvest(struct vtrnd_softc *sc)
191 {
192 struct sglist_seg segs[1];
193 struct sglist sg;
194 struct virtqueue *vq;
195 uint32_t value;
196 int error;
197
198 vq = sc->vtrnd_vq;
199
200 sglist_init(&sg, 1, segs);
201 error = sglist_append(&sg, &value, sizeof(value));
202 KASSERT(error == 0 && sg.sg_nseg == 1,
203 ("%s: error %d adding buffer to sglist", __func__, error));
204
205 if (!virtqueue_empty(vq))
206 return;
207 if (virtqueue_enqueue(vq, &value, &sg, 0, 1) != 0)
208 return;
209
210 /*
211 * Poll for the response, but the command is likely already
212 * done when we return from the notify.
213 */
214 virtqueue_notify(vq, NULL);
215 virtqueue_poll(vq, NULL);
216
217 add_buffer_randomness_src((const char *)&value, sizeof(value),
218 RAND_SRC_VIRTIO);
219 }
220
221 static void
vtrnd_timer(void * xsc)222 vtrnd_timer(void *xsc)
223 {
224 struct vtrnd_softc *sc;
225
226 sc = xsc;
227
228 vtrnd_harvest(sc);
229 callout_reset(&sc->vtrnd_callout, 5 * hz, vtrnd_timer, sc);
230 }
231