1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
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
29 /* Driver for VirtIO entropy device. */
30
31 #include <sys/param.h>
32 #include <sys/types.h>
33 #include <sys/eventhandler.h>
34 #include <sys/kernel.h>
35 #include <sys/malloc.h>
36 #include <sys/module.h>
37 #include <sys/sglist.h>
38 #include <sys/random.h>
39 #include <sys/stdatomic.h>
40
41 #include <machine/bus.h>
42 #include <machine/resource.h>
43 #include <sys/bus.h>
44
45 #include <dev/random/randomdev.h>
46 #include <dev/random/random_harvestq.h>
47 #include <dev/virtio/virtio.h>
48 #include <dev/virtio/virtqueue.h>
49
50 struct vtrnd_softc {
51 device_t vtrnd_dev;
52 uint64_t vtrnd_features;
53 struct virtqueue *vtrnd_vq;
54 eventhandler_tag eh;
55 bool inactive;
56 struct sglist *vtrnd_sg;
57 uint32_t *vtrnd_value;
58 };
59
60 static int vtrnd_modevent(module_t, int, void *);
61
62 static int vtrnd_probe(device_t);
63 static int vtrnd_attach(device_t);
64 static int vtrnd_detach(device_t);
65 static int vtrnd_shutdown(device_t);
66
67 static int vtrnd_negotiate_features(struct vtrnd_softc *);
68 static int vtrnd_setup_features(struct vtrnd_softc *);
69 static int vtrnd_alloc_virtqueue(struct vtrnd_softc *);
70 static int vtrnd_harvest(struct vtrnd_softc *, void *, size_t *);
71 static void vtrnd_enqueue(struct vtrnd_softc *sc);
72 static unsigned vtrnd_read(void *, unsigned);
73
74 #define VTRND_FEATURES 0
75
76 static struct virtio_feature_desc vtrnd_feature_desc[] = {
77 { 0, NULL }
78 };
79
80 static struct random_source random_vtrnd = {
81 .rs_ident = "VirtIO Entropy Adapter",
82 .rs_source = RANDOM_PURE_VIRTIO,
83 .rs_read = vtrnd_read,
84 };
85
86 /* Kludge for API limitations of random(4). */
87 static _Atomic(struct vtrnd_softc *) g_vtrnd_softc;
88
89 static device_method_t vtrnd_methods[] = {
90 /* Device methods. */
91 DEVMETHOD(device_probe, vtrnd_probe),
92 DEVMETHOD(device_attach, vtrnd_attach),
93 DEVMETHOD(device_detach, vtrnd_detach),
94 DEVMETHOD(device_shutdown, vtrnd_shutdown),
95
96 DEVMETHOD_END
97 };
98
99 static driver_t vtrnd_driver = {
100 "vtrnd",
101 vtrnd_methods,
102 sizeof(struct vtrnd_softc)
103 };
104
105 VIRTIO_DRIVER_MODULE(virtio_random, vtrnd_driver, vtrnd_modevent, NULL);
106 MODULE_VERSION(virtio_random, 1);
107 MODULE_DEPEND(virtio_random, virtio, 1, 1, 1);
108 MODULE_DEPEND(virtio_random, random_device, 1, 1, 1);
109
110 VIRTIO_SIMPLE_PNPINFO(virtio_random, VIRTIO_ID_ENTROPY,
111 "VirtIO Entropy Adapter");
112
113 static int
vtrnd_modevent(module_t mod,int type,void * unused)114 vtrnd_modevent(module_t mod, int type, void *unused)
115 {
116 int error;
117
118 switch (type) {
119 case MOD_LOAD:
120 case MOD_QUIESCE:
121 case MOD_UNLOAD:
122 case MOD_SHUTDOWN:
123 error = 0;
124 break;
125 default:
126 error = EOPNOTSUPP;
127 break;
128 }
129
130 return (error);
131 }
132
133 static int
vtrnd_probe(device_t dev)134 vtrnd_probe(device_t dev)
135 {
136 return (VIRTIO_SIMPLE_PROBE(dev, virtio_random));
137 }
138
139 static int
vtrnd_attach(device_t dev)140 vtrnd_attach(device_t dev)
141 {
142 struct vtrnd_softc *sc, *exp;
143 size_t len;
144 int error;
145
146 sc = device_get_softc(dev);
147 sc->vtrnd_dev = dev;
148 virtio_set_feature_desc(dev, vtrnd_feature_desc);
149
150 len = sizeof(*sc->vtrnd_value) * HARVESTSIZE;
151 sc->vtrnd_value = malloc_aligned(len, len, M_DEVBUF, M_WAITOK);
152 sc->vtrnd_sg = sglist_build(sc->vtrnd_value, len, M_WAITOK);
153
154 error = vtrnd_setup_features(sc);
155 if (error) {
156 device_printf(dev, "cannot setup features\n");
157 goto fail;
158 }
159
160 error = vtrnd_alloc_virtqueue(sc);
161 if (error) {
162 device_printf(dev, "cannot allocate virtqueue\n");
163 goto fail;
164 }
165
166 exp = NULL;
167 if (!atomic_compare_exchange_strong_explicit(&g_vtrnd_softc, &exp, sc,
168 memory_order_release, memory_order_acquire)) {
169 error = EEXIST;
170 goto fail;
171 }
172
173 sc->eh = EVENTHANDLER_REGISTER(shutdown_post_sync,
174 vtrnd_shutdown, dev, SHUTDOWN_PRI_LAST + 1); /* ??? */
175 if (sc->eh == NULL) {
176 device_printf(dev, "Shutdown event registration failed\n");
177 error = ENXIO;
178 goto fail;
179 }
180
181 sc->inactive = false;
182 random_source_register(&random_vtrnd);
183
184 vtrnd_enqueue(sc);
185
186 fail:
187 if (error)
188 vtrnd_detach(dev);
189
190 return (error);
191 }
192
193 static int
vtrnd_detach(device_t dev)194 vtrnd_detach(device_t dev)
195 {
196 struct vtrnd_softc *sc;
197 uint32_t rdlen;
198
199 sc = device_get_softc(dev);
200 KASSERT(
201 atomic_load_explicit(&g_vtrnd_softc, memory_order_acquire) == sc,
202 ("only one global instance at a time"));
203
204 sc->inactive = true;
205 if (sc->eh != NULL) {
206 EVENTHANDLER_DEREGISTER(shutdown_post_sync, sc->eh);
207 sc->eh = NULL;
208 }
209 random_source_deregister(&random_vtrnd);
210
211 /* clear the queue */
212 virtqueue_poll(sc->vtrnd_vq, &rdlen);
213
214 atomic_store_explicit(&g_vtrnd_softc, NULL, memory_order_release);
215 sglist_free(sc->vtrnd_sg);
216 zfree(sc->vtrnd_value, M_DEVBUF);
217 return (0);
218 }
219
220 static int
vtrnd_shutdown(device_t dev)221 vtrnd_shutdown(device_t dev)
222 {
223 struct vtrnd_softc *sc;
224
225 sc = device_get_softc(dev);
226 sc->inactive = true;
227
228 return(0);
229 }
230
231 static int
vtrnd_negotiate_features(struct vtrnd_softc * sc)232 vtrnd_negotiate_features(struct vtrnd_softc *sc)
233 {
234 device_t dev;
235 uint64_t features;
236
237 dev = sc->vtrnd_dev;
238 features = VTRND_FEATURES;
239
240 sc->vtrnd_features = virtio_negotiate_features(dev, features);
241 return (virtio_finalize_features(dev));
242 }
243
244 static int
vtrnd_setup_features(struct vtrnd_softc * sc)245 vtrnd_setup_features(struct vtrnd_softc *sc)
246 {
247 int error;
248
249 error = vtrnd_negotiate_features(sc);
250 if (error)
251 return (error);
252
253 return (0);
254 }
255
256 static int
vtrnd_alloc_virtqueue(struct vtrnd_softc * sc)257 vtrnd_alloc_virtqueue(struct vtrnd_softc *sc)
258 {
259 device_t dev;
260 struct vq_alloc_info vq_info;
261
262 dev = sc->vtrnd_dev;
263
264 VQ_ALLOC_INFO_INIT(&vq_info, 0, NULL, sc, &sc->vtrnd_vq,
265 "%s request", device_get_nameunit(dev));
266
267 return (virtio_alloc_virtqueues(dev, 1, &vq_info));
268 }
269
270 static void
vtrnd_enqueue(struct vtrnd_softc * sc)271 vtrnd_enqueue(struct vtrnd_softc *sc)
272 {
273 struct virtqueue *vq;
274 int error __diagused;
275
276 vq = sc->vtrnd_vq;
277
278 KASSERT(virtqueue_empty(vq), ("%s: non-empty queue", __func__));
279
280 error = virtqueue_enqueue(vq, sc, sc->vtrnd_sg, 0, 1);
281 KASSERT(error == 0, ("%s: virtqueue_enqueue returned error: %d",
282 __func__, error));
283
284 virtqueue_notify(vq);
285 }
286
287 static int
vtrnd_harvest(struct vtrnd_softc * sc,void * buf,size_t * sz)288 vtrnd_harvest(struct vtrnd_softc *sc, void *buf, size_t *sz)
289 {
290 struct virtqueue *vq;
291 void *cookie;
292 uint32_t rdlen;
293
294 if (sc->inactive)
295 return (EDEADLK);
296
297 vq = sc->vtrnd_vq;
298
299 cookie = virtqueue_dequeue(vq, &rdlen);
300 if (cookie == NULL)
301 return (EAGAIN);
302 KASSERT(cookie == sc, ("%s: cookie mismatch", __func__));
303
304 *sz = MIN(rdlen, *sz);
305 memcpy(buf, sc->vtrnd_value, *sz);
306
307 vtrnd_enqueue(sc);
308
309 return (0);
310 }
311
312 static unsigned
vtrnd_read(void * buf,unsigned usz)313 vtrnd_read(void *buf, unsigned usz)
314 {
315 struct vtrnd_softc *sc;
316 size_t sz;
317 int error;
318
319 sc = g_vtrnd_softc;
320 if (sc == NULL)
321 return (0);
322
323 sz = usz;
324 error = vtrnd_harvest(sc, buf, &sz);
325 if (error != 0)
326 return (0);
327
328 return (sz);
329 }
330