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/kernel.h> 36 #include <sys/malloc.h> 37 #include <sys/module.h> 38 #include <sys/sglist.h> 39 #include <sys/random.h> 40 #include <sys/stdatomic.h> 41 42 #include <machine/bus.h> 43 #include <machine/resource.h> 44 #include <sys/bus.h> 45 46 #include <dev/random/randomdev.h> 47 #include <dev/random/random_harvestq.h> 48 #include <dev/virtio/virtio.h> 49 #include <dev/virtio/virtqueue.h> 50 51 struct vtrnd_softc { 52 device_t vtrnd_dev; 53 uint64_t vtrnd_features; 54 struct virtqueue *vtrnd_vq; 55 }; 56 57 static int vtrnd_modevent(module_t, int, void *); 58 59 static int vtrnd_probe(device_t); 60 static int vtrnd_attach(device_t); 61 static int vtrnd_detach(device_t); 62 63 static int vtrnd_negotiate_features(struct vtrnd_softc *); 64 static int vtrnd_setup_features(struct vtrnd_softc *); 65 static int vtrnd_alloc_virtqueue(struct vtrnd_softc *); 66 static int vtrnd_harvest(struct vtrnd_softc *, void *, size_t *); 67 static unsigned vtrnd_read(void *, unsigned); 68 69 #define VTRND_FEATURES 0 70 71 static struct virtio_feature_desc vtrnd_feature_desc[] = { 72 { 0, NULL } 73 }; 74 75 static struct random_source random_vtrnd = { 76 .rs_ident = "VirtIO Entropy Adapter", 77 .rs_source = RANDOM_PURE_VIRTIO, 78 .rs_read = vtrnd_read, 79 }; 80 81 /* Kludge for API limitations of random(4). */ 82 static _Atomic(struct vtrnd_softc *) g_vtrnd_softc; 83 84 static device_method_t vtrnd_methods[] = { 85 /* Device methods. */ 86 DEVMETHOD(device_probe, vtrnd_probe), 87 DEVMETHOD(device_attach, vtrnd_attach), 88 DEVMETHOD(device_detach, vtrnd_detach), 89 90 DEVMETHOD_END 91 }; 92 93 static driver_t vtrnd_driver = { 94 "vtrnd", 95 vtrnd_methods, 96 sizeof(struct vtrnd_softc) 97 }; 98 static devclass_t vtrnd_devclass; 99 100 VIRTIO_DRIVER_MODULE(virtio_random, vtrnd_driver, vtrnd_devclass, 101 vtrnd_modevent, 0); 102 MODULE_VERSION(virtio_random, 1); 103 MODULE_DEPEND(virtio_random, virtio, 1, 1, 1); 104 MODULE_DEPEND(virtio_random, random_device, 1, 1, 1); 105 106 VIRTIO_SIMPLE_PNPINFO(virtio_random, VIRTIO_ID_ENTROPY, 107 "VirtIO Entropy Adapter"); 108 109 static int 110 vtrnd_modevent(module_t mod, int type, void *unused) 111 { 112 int error; 113 114 switch (type) { 115 case MOD_LOAD: 116 case MOD_QUIESCE: 117 case MOD_UNLOAD: 118 case MOD_SHUTDOWN: 119 error = 0; 120 break; 121 default: 122 error = EOPNOTSUPP; 123 break; 124 } 125 126 return (error); 127 } 128 129 static int 130 vtrnd_probe(device_t dev) 131 { 132 return (VIRTIO_SIMPLE_PROBE(dev, virtio_random)); 133 } 134 135 static int 136 vtrnd_attach(device_t dev) 137 { 138 struct vtrnd_softc *sc, *exp; 139 int error; 140 141 sc = device_get_softc(dev); 142 sc->vtrnd_dev = dev; 143 virtio_set_feature_desc(dev, vtrnd_feature_desc); 144 145 error = vtrnd_setup_features(sc); 146 if (error) { 147 device_printf(dev, "cannot setup features\n"); 148 goto fail; 149 } 150 151 error = vtrnd_alloc_virtqueue(sc); 152 if (error) { 153 device_printf(dev, "cannot allocate virtqueue\n"); 154 goto fail; 155 } 156 157 exp = NULL; 158 if (!atomic_compare_exchange_strong_explicit(&g_vtrnd_softc, &exp, sc, 159 memory_order_release, memory_order_acquire)) { 160 error = EEXIST; 161 goto fail; 162 } 163 random_source_register(&random_vtrnd); 164 165 fail: 166 if (error) 167 vtrnd_detach(dev); 168 169 return (error); 170 } 171 172 static int 173 vtrnd_detach(device_t dev) 174 { 175 struct vtrnd_softc *sc; 176 177 sc = device_get_softc(dev); 178 KASSERT( 179 atomic_load_explicit(&g_vtrnd_softc, memory_order_acquire) == sc, 180 ("only one global instance at a time")); 181 182 random_source_deregister(&random_vtrnd); 183 atomic_store_explicit(&g_vtrnd_softc, NULL, memory_order_release); 184 return (0); 185 } 186 187 static int 188 vtrnd_negotiate_features(struct vtrnd_softc *sc) 189 { 190 device_t dev; 191 uint64_t features; 192 193 dev = sc->vtrnd_dev; 194 features = VTRND_FEATURES; 195 196 sc->vtrnd_features = virtio_negotiate_features(dev, features); 197 return (virtio_finalize_features(dev)); 198 } 199 200 static int 201 vtrnd_setup_features(struct vtrnd_softc *sc) 202 { 203 int error; 204 205 error = vtrnd_negotiate_features(sc); 206 if (error) 207 return (error); 208 209 return (0); 210 } 211 212 static int 213 vtrnd_alloc_virtqueue(struct vtrnd_softc *sc) 214 { 215 device_t dev; 216 struct vq_alloc_info vq_info; 217 218 dev = sc->vtrnd_dev; 219 220 VQ_ALLOC_INFO_INIT(&vq_info, 0, NULL, sc, &sc->vtrnd_vq, 221 "%s request", device_get_nameunit(dev)); 222 223 return (virtio_alloc_virtqueues(dev, 0, 1, &vq_info)); 224 } 225 226 static int 227 vtrnd_harvest(struct vtrnd_softc *sc, void *buf, size_t *sz) 228 { 229 struct sglist_seg segs[1]; 230 struct sglist sg; 231 struct virtqueue *vq; 232 uint32_t value[HARVESTSIZE] __aligned(sizeof(uint32_t) * HARVESTSIZE); 233 uint32_t rdlen; 234 int error; 235 236 _Static_assert(sizeof(value) < PAGE_SIZE, "sglist assumption"); 237 238 sglist_init(&sg, 1, segs); 239 error = sglist_append(&sg, value, *sz); 240 if (error != 0) 241 panic("%s: sglist_append error=%d", __func__, error); 242 243 vq = sc->vtrnd_vq; 244 KASSERT(virtqueue_empty(vq), ("%s: non-empty queue", __func__)); 245 246 error = virtqueue_enqueue(vq, buf, &sg, 0, 1); 247 if (error != 0) 248 return (error); 249 250 /* 251 * Poll for the response, but the command is likely already 252 * done when we return from the notify. 253 */ 254 virtqueue_notify(vq); 255 virtqueue_poll(vq, &rdlen); 256 257 if (rdlen > *sz) 258 panic("%s: random device wrote %zu bytes beyond end of provided" 259 " buffer %p:%zu", __func__, (size_t)rdlen - *sz, 260 (void *)value, *sz); 261 else if (rdlen == 0) 262 return (EAGAIN); 263 *sz = MIN(rdlen, *sz); 264 memcpy(buf, value, *sz); 265 explicit_bzero(value, *sz); 266 return (0); 267 } 268 269 static unsigned 270 vtrnd_read(void *buf, unsigned usz) 271 { 272 struct vtrnd_softc *sc; 273 size_t sz; 274 int error; 275 276 sc = g_vtrnd_softc; 277 if (sc == NULL) 278 return (0); 279 280 sz = usz; 281 error = vtrnd_harvest(sc, buf, &sz); 282 if (error != 0) 283 return (0); 284 285 return (sz); 286 } 287