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 29 /* Driver for VirtIO entropy device. */ 30 31 #include <sys/cdefs.h> 32 __FBSDID("$FreeBSD$"); 33 34 #include <sys/param.h> 35 #include <sys/types.h> 36 #include <sys/eventhandler.h> 37 #include <sys/kernel.h> 38 #include <sys/malloc.h> 39 #include <sys/module.h> 40 #include <sys/sglist.h> 41 #include <sys/random.h> 42 #include <sys/stdatomic.h> 43 44 #include <machine/bus.h> 45 #include <machine/resource.h> 46 #include <sys/bus.h> 47 48 #include <dev/random/randomdev.h> 49 #include <dev/random/random_harvestq.h> 50 #include <dev/virtio/virtio.h> 51 #include <dev/virtio/virtqueue.h> 52 53 struct vtrnd_softc { 54 device_t vtrnd_dev; 55 uint64_t vtrnd_features; 56 struct virtqueue *vtrnd_vq; 57 eventhandler_tag eh; 58 bool inactive; 59 }; 60 61 static int vtrnd_modevent(module_t, int, void *); 62 63 static int vtrnd_probe(device_t); 64 static int vtrnd_attach(device_t); 65 static int vtrnd_detach(device_t); 66 static int vtrnd_shutdown(device_t); 67 68 static int vtrnd_negotiate_features(struct vtrnd_softc *); 69 static int vtrnd_setup_features(struct vtrnd_softc *); 70 static int vtrnd_alloc_virtqueue(struct vtrnd_softc *); 71 static int vtrnd_harvest(struct vtrnd_softc *, void *, size_t *); 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 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 134 vtrnd_probe(device_t dev) 135 { 136 return (VIRTIO_SIMPLE_PROBE(dev, virtio_random)); 137 } 138 139 static int 140 vtrnd_attach(device_t dev) 141 { 142 struct vtrnd_softc *sc, *exp; 143 int error; 144 145 sc = device_get_softc(dev); 146 sc->vtrnd_dev = dev; 147 virtio_set_feature_desc(dev, vtrnd_feature_desc); 148 149 error = vtrnd_setup_features(sc); 150 if (error) { 151 device_printf(dev, "cannot setup features\n"); 152 goto fail; 153 } 154 155 error = vtrnd_alloc_virtqueue(sc); 156 if (error) { 157 device_printf(dev, "cannot allocate virtqueue\n"); 158 goto fail; 159 } 160 161 exp = NULL; 162 if (!atomic_compare_exchange_strong_explicit(&g_vtrnd_softc, &exp, sc, 163 memory_order_release, memory_order_acquire)) { 164 error = EEXIST; 165 goto fail; 166 } 167 168 sc->eh = EVENTHANDLER_REGISTER(shutdown_post_sync, 169 vtrnd_shutdown, dev, SHUTDOWN_PRI_LAST + 1); /* ??? */ 170 if (sc->eh == NULL) { 171 device_printf(dev, "Shutdown event registration failed\n"); 172 error = ENXIO; 173 goto fail; 174 } 175 176 sc->inactive = false; 177 random_source_register(&random_vtrnd); 178 179 fail: 180 if (error) 181 vtrnd_detach(dev); 182 183 return (error); 184 } 185 186 static int 187 vtrnd_detach(device_t dev) 188 { 189 struct vtrnd_softc *sc; 190 191 sc = device_get_softc(dev); 192 KASSERT( 193 atomic_load_explicit(&g_vtrnd_softc, memory_order_acquire) == sc, 194 ("only one global instance at a time")); 195 196 sc->inactive = true; 197 if (sc->eh != NULL) { 198 EVENTHANDLER_DEREGISTER(shutdown_post_sync, sc->eh); 199 sc->eh = NULL; 200 } 201 random_source_deregister(&random_vtrnd); 202 atomic_store_explicit(&g_vtrnd_softc, NULL, memory_order_release); 203 return (0); 204 } 205 206 static int 207 vtrnd_shutdown(device_t dev) 208 { 209 struct vtrnd_softc *sc; 210 211 sc = device_get_softc(dev); 212 sc->inactive = true; 213 214 return(0); 215 } 216 217 static int 218 vtrnd_negotiate_features(struct vtrnd_softc *sc) 219 { 220 device_t dev; 221 uint64_t features; 222 223 dev = sc->vtrnd_dev; 224 features = VTRND_FEATURES; 225 226 sc->vtrnd_features = virtio_negotiate_features(dev, features); 227 return (virtio_finalize_features(dev)); 228 } 229 230 static int 231 vtrnd_setup_features(struct vtrnd_softc *sc) 232 { 233 int error; 234 235 error = vtrnd_negotiate_features(sc); 236 if (error) 237 return (error); 238 239 return (0); 240 } 241 242 static int 243 vtrnd_alloc_virtqueue(struct vtrnd_softc *sc) 244 { 245 device_t dev; 246 struct vq_alloc_info vq_info; 247 248 dev = sc->vtrnd_dev; 249 250 VQ_ALLOC_INFO_INIT(&vq_info, 0, NULL, sc, &sc->vtrnd_vq, 251 "%s request", device_get_nameunit(dev)); 252 253 return (virtio_alloc_virtqueues(dev, 0, 1, &vq_info)); 254 } 255 256 static int 257 vtrnd_harvest(struct vtrnd_softc *sc, void *buf, size_t *sz) 258 { 259 struct sglist_seg segs[1]; 260 struct sglist sg; 261 struct virtqueue *vq; 262 uint32_t value[HARVESTSIZE] __aligned(sizeof(uint32_t) * HARVESTSIZE); 263 uint32_t rdlen; 264 int error; 265 266 _Static_assert(sizeof(value) < PAGE_SIZE, "sglist assumption"); 267 268 if (sc->inactive) 269 return (EDEADLK); 270 271 sglist_init(&sg, 1, segs); 272 error = sglist_append(&sg, value, *sz); 273 if (error != 0) 274 panic("%s: sglist_append error=%d", __func__, error); 275 276 vq = sc->vtrnd_vq; 277 KASSERT(virtqueue_empty(vq), ("%s: non-empty queue", __func__)); 278 279 error = virtqueue_enqueue(vq, buf, &sg, 0, 1); 280 if (error != 0) 281 return (error); 282 283 /* 284 * Poll for the response, but the command is likely already 285 * done when we return from the notify. 286 */ 287 virtqueue_notify(vq); 288 virtqueue_poll(vq, &rdlen); 289 290 if (rdlen > *sz) 291 panic("%s: random device wrote %zu bytes beyond end of provided" 292 " buffer %p:%zu", __func__, (size_t)rdlen - *sz, 293 (void *)value, *sz); 294 else if (rdlen == 0) 295 return (EAGAIN); 296 *sz = MIN(rdlen, *sz); 297 memcpy(buf, value, *sz); 298 explicit_bzero(value, *sz); 299 return (0); 300 } 301 302 static unsigned 303 vtrnd_read(void *buf, unsigned usz) 304 { 305 struct vtrnd_softc *sc; 306 size_t sz; 307 int error; 308 309 sc = g_vtrnd_softc; 310 if (sc == NULL) 311 return (0); 312 313 sz = usz; 314 error = vtrnd_harvest(sc, buf, &sz); 315 if (error != 0) 316 return (0); 317 318 return (sz); 319 } 320