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 static devclass_t vtrnd_devclass; 105 106 VIRTIO_DRIVER_MODULE(virtio_random, vtrnd_driver, vtrnd_devclass, 107 vtrnd_modevent, 0); 108 MODULE_VERSION(virtio_random, 1); 109 MODULE_DEPEND(virtio_random, virtio, 1, 1, 1); 110 MODULE_DEPEND(virtio_random, random_device, 1, 1, 1); 111 112 VIRTIO_SIMPLE_PNPINFO(virtio_random, VIRTIO_ID_ENTROPY, 113 "VirtIO Entropy Adapter"); 114 115 static int 116 vtrnd_modevent(module_t mod, int type, void *unused) 117 { 118 int error; 119 120 switch (type) { 121 case MOD_LOAD: 122 case MOD_QUIESCE: 123 case MOD_UNLOAD: 124 case MOD_SHUTDOWN: 125 error = 0; 126 break; 127 default: 128 error = EOPNOTSUPP; 129 break; 130 } 131 132 return (error); 133 } 134 135 static int 136 vtrnd_probe(device_t dev) 137 { 138 return (VIRTIO_SIMPLE_PROBE(dev, virtio_random)); 139 } 140 141 static int 142 vtrnd_attach(device_t dev) 143 { 144 struct vtrnd_softc *sc, *exp; 145 int error; 146 147 sc = device_get_softc(dev); 148 sc->vtrnd_dev = dev; 149 virtio_set_feature_desc(dev, vtrnd_feature_desc); 150 151 error = vtrnd_setup_features(sc); 152 if (error) { 153 device_printf(dev, "cannot setup features\n"); 154 goto fail; 155 } 156 157 error = vtrnd_alloc_virtqueue(sc); 158 if (error) { 159 device_printf(dev, "cannot allocate virtqueue\n"); 160 goto fail; 161 } 162 163 exp = NULL; 164 if (!atomic_compare_exchange_strong_explicit(&g_vtrnd_softc, &exp, sc, 165 memory_order_release, memory_order_acquire)) { 166 error = EEXIST; 167 goto fail; 168 } 169 170 sc->eh = EVENTHANDLER_REGISTER(shutdown_post_sync, 171 vtrnd_shutdown, dev, SHUTDOWN_PRI_LAST + 1); /* ??? */ 172 if (sc->eh == NULL) { 173 device_printf(dev, "Shutdown event registration failed\n"); 174 error = ENXIO; 175 goto fail; 176 } 177 178 sc->inactive = false; 179 random_source_register(&random_vtrnd); 180 181 fail: 182 if (error) 183 vtrnd_detach(dev); 184 185 return (error); 186 } 187 188 static int 189 vtrnd_detach(device_t dev) 190 { 191 struct vtrnd_softc *sc; 192 193 sc = device_get_softc(dev); 194 KASSERT( 195 atomic_load_explicit(&g_vtrnd_softc, memory_order_acquire) == sc, 196 ("only one global instance at a time")); 197 198 sc->inactive = true; 199 if (sc->eh != NULL) { 200 EVENTHANDLER_DEREGISTER(shutdown_post_sync, sc->eh); 201 sc->eh = NULL; 202 } 203 random_source_deregister(&random_vtrnd); 204 atomic_store_explicit(&g_vtrnd_softc, NULL, memory_order_release); 205 return (0); 206 } 207 208 static int 209 vtrnd_shutdown(device_t dev) 210 { 211 struct vtrnd_softc *sc; 212 213 sc = device_get_softc(dev); 214 sc->inactive = true; 215 216 return(0); 217 } 218 219 static int 220 vtrnd_negotiate_features(struct vtrnd_softc *sc) 221 { 222 device_t dev; 223 uint64_t features; 224 225 dev = sc->vtrnd_dev; 226 features = VTRND_FEATURES; 227 228 sc->vtrnd_features = virtio_negotiate_features(dev, features); 229 return (virtio_finalize_features(dev)); 230 } 231 232 static int 233 vtrnd_setup_features(struct vtrnd_softc *sc) 234 { 235 int error; 236 237 error = vtrnd_negotiate_features(sc); 238 if (error) 239 return (error); 240 241 return (0); 242 } 243 244 static int 245 vtrnd_alloc_virtqueue(struct vtrnd_softc *sc) 246 { 247 device_t dev; 248 struct vq_alloc_info vq_info; 249 250 dev = sc->vtrnd_dev; 251 252 VQ_ALLOC_INFO_INIT(&vq_info, 0, NULL, sc, &sc->vtrnd_vq, 253 "%s request", device_get_nameunit(dev)); 254 255 return (virtio_alloc_virtqueues(dev, 0, 1, &vq_info)); 256 } 257 258 static int 259 vtrnd_harvest(struct vtrnd_softc *sc, void *buf, size_t *sz) 260 { 261 struct sglist_seg segs[1]; 262 struct sglist sg; 263 struct virtqueue *vq; 264 uint32_t value[HARVESTSIZE] __aligned(sizeof(uint32_t) * HARVESTSIZE); 265 uint32_t rdlen; 266 int error; 267 268 _Static_assert(sizeof(value) < PAGE_SIZE, "sglist assumption"); 269 270 if (sc->inactive) 271 return (EDEADLK); 272 273 sglist_init(&sg, 1, segs); 274 error = sglist_append(&sg, value, *sz); 275 if (error != 0) 276 panic("%s: sglist_append error=%d", __func__, error); 277 278 vq = sc->vtrnd_vq; 279 KASSERT(virtqueue_empty(vq), ("%s: non-empty queue", __func__)); 280 281 error = virtqueue_enqueue(vq, buf, &sg, 0, 1); 282 if (error != 0) 283 return (error); 284 285 /* 286 * Poll for the response, but the command is likely already 287 * done when we return from the notify. 288 */ 289 virtqueue_notify(vq); 290 virtqueue_poll(vq, &rdlen); 291 292 if (rdlen > *sz) 293 panic("%s: random device wrote %zu bytes beyond end of provided" 294 " buffer %p:%zu", __func__, (size_t)rdlen - *sz, 295 (void *)value, *sz); 296 else if (rdlen == 0) 297 return (EAGAIN); 298 *sz = MIN(rdlen, *sz); 299 memcpy(buf, value, *sz); 300 explicit_bzero(value, *sz); 301 return (0); 302 } 303 304 static unsigned 305 vtrnd_read(void *buf, unsigned usz) 306 { 307 struct vtrnd_softc *sc; 308 size_t sz; 309 int error; 310 311 sc = g_vtrnd_softc; 312 if (sc == NULL) 313 return (0); 314 315 sz = usz; 316 error = vtrnd_harvest(sc, buf, &sz); 317 if (error != 0) 318 return (0); 319 320 return (sz); 321 } 322