1 /* $OpenBSD: viornd.c,v 1.3 2019/05/26 15:20:04 sf Exp $ */ 2 3 /* 4 * Copyright (c) 2014 Stefan Fritsch <sf@sfritsch.de> 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19 #include <sys/param.h> 20 #include <sys/systm.h> 21 #include <sys/kernel.h> 22 #include <sys/timeout.h> 23 #include <machine/bus.h> 24 #include <sys/device.h> 25 #include <sys/pool.h> 26 #include <dev/rndvar.h> 27 #include <dev/pv/virtioreg.h> 28 #include <dev/pv/virtiovar.h> 29 30 /* 31 * The host may not have an unlimited supply of entropy. Therefore, we must 32 * not blindly get as much entropy as we can. Instead, we just request 33 * VIORND_BUFSIZE bytes at boot and every 15 * (1 << interval_shift) seconds. 34 * XXX There should be an API to check if we actually need more entropy. 35 * 36 * The lowest byte in the flags is used for transport specific settings. 37 * Therefore we use the second byte. 38 */ 39 #define VIORND_INTERVAL_SHIFT(f) ((f >> 8) & 0xf) 40 #define VIORND_INTERVAL_SHIFT_DEFAULT 5 41 #define VIORND_ONESHOT 0x1000 42 #define VIORND_BUFSIZE 16 43 44 #define VIORND_DEBUG 0 45 46 struct viornd_softc { 47 struct device sc_dev; 48 struct virtio_softc *sc_virtio; 49 50 struct virtqueue sc_vq; 51 int *sc_buf; 52 bus_dmamap_t sc_dmamap; 53 54 unsigned int sc_interval; 55 struct timeout sc_tick; 56 }; 57 58 int viornd_match(struct device *, void *, void *); 59 void viornd_attach(struct device *, struct device *, void *); 60 int viornd_vq_done(struct virtqueue *); 61 void viornd_tick(void *); 62 63 struct cfattach viornd_ca = { 64 sizeof(struct viornd_softc), 65 viornd_match, 66 viornd_attach, 67 NULL 68 }; 69 70 struct cfdriver viornd_cd = { 71 NULL, "viornd", DV_DULL 72 }; 73 74 75 int viornd_match(struct device *parent, void *match, void *aux) 76 { 77 struct virtio_softc *va = aux; 78 if (va->sc_childdevid == PCI_PRODUCT_VIRTIO_ENTROPY) 79 return 1; 80 return 0; 81 } 82 83 void 84 viornd_attach(struct device *parent, struct device *self, void *aux) 85 { 86 struct viornd_softc *sc = (struct viornd_softc *)self; 87 struct virtio_softc *vsc = (struct virtio_softc *)parent; 88 unsigned int shift; 89 90 vsc->sc_vqs = &sc->sc_vq; 91 vsc->sc_nvqs = 1; 92 vsc->sc_config_change = 0; 93 if (vsc->sc_child != NULL) 94 panic("already attached to something else"); 95 vsc->sc_child = self; 96 vsc->sc_ipl = IPL_NET; 97 sc->sc_virtio = vsc; 98 99 virtio_negotiate_features(vsc, NULL); 100 101 if (sc->sc_dev.dv_cfdata->cf_flags & VIORND_ONESHOT) { 102 sc->sc_interval = 0; 103 } else { 104 shift = VIORND_INTERVAL_SHIFT(sc->sc_dev.dv_cfdata->cf_flags); 105 if (shift == 0) 106 shift = VIORND_INTERVAL_SHIFT_DEFAULT; 107 sc->sc_interval = 15 * (1 << shift); 108 } 109 #if VIORND_DEBUG 110 printf(": request interval: %us\n", sc->sc_interval); 111 #endif 112 113 sc->sc_buf = dma_alloc(VIORND_BUFSIZE, PR_NOWAIT|PR_ZERO); 114 if (sc->sc_buf == NULL) { 115 printf(": Can't alloc dma buffer\n"); 116 goto err; 117 } 118 if (bus_dmamap_create(sc->sc_virtio->sc_dmat, VIORND_BUFSIZE, 1, 119 VIORND_BUFSIZE, 0, BUS_DMA_NOWAIT|BUS_DMA_ALLOCNOW, 120 &sc->sc_dmamap)) { 121 printf(": Can't alloc dmamap\n"); 122 goto err; 123 } 124 if (bus_dmamap_load(sc->sc_virtio->sc_dmat, sc->sc_dmamap, 125 sc->sc_buf, VIORND_BUFSIZE, NULL, BUS_DMA_NOWAIT|BUS_DMA_READ)) { 126 printf(": Can't load dmamap\n"); 127 goto err2; 128 } 129 130 if (virtio_alloc_vq(vsc, &sc->sc_vq, 0, VIORND_BUFSIZE, 1, 131 "Entropy request") != 0) { 132 printf(": Can't alloc virtqueue\n"); 133 goto err2; 134 } 135 136 sc->sc_vq.vq_done = viornd_vq_done; 137 virtio_start_vq_intr(vsc, &sc->sc_vq); 138 timeout_set(&sc->sc_tick, viornd_tick, sc); 139 timeout_add(&sc->sc_tick, 1); 140 141 printf("\n"); 142 return; 143 err2: 144 bus_dmamap_destroy(vsc->sc_dmat, sc->sc_dmamap); 145 err: 146 vsc->sc_child = VIRTIO_CHILD_ERROR; 147 if (sc->sc_buf != NULL) { 148 dma_free(sc->sc_buf, VIORND_BUFSIZE); 149 sc->sc_buf = NULL; 150 } 151 return; 152 } 153 154 int 155 viornd_vq_done(struct virtqueue *vq) 156 { 157 struct virtio_softc *vsc = vq->vq_owner; 158 struct viornd_softc *sc = (struct viornd_softc *)vsc->sc_child; 159 int slot, len, i; 160 161 if (virtio_dequeue(vsc, vq, &slot, &len) != 0) 162 return 0; 163 bus_dmamap_sync(vsc->sc_dmat, sc->sc_dmamap, 0, VIORND_BUFSIZE, 164 BUS_DMASYNC_POSTREAD); 165 if (len > VIORND_BUFSIZE) { 166 printf("%s: inconsistent descriptor length %d > %d\n", 167 sc->sc_dev.dv_xname, len, VIORND_BUFSIZE); 168 goto out; 169 } 170 171 #if VIORND_DEBUG 172 printf("%s: got %d bytes of entropy\n", __func__, len); 173 #endif 174 for (i = 0; (i + 1) * sizeof(int) <= len; i++) 175 enqueue_randomness(sc->sc_buf[i]); 176 177 if (sc->sc_interval) 178 timeout_add_sec(&sc->sc_tick, sc->sc_interval); 179 180 out: 181 virtio_dequeue_commit(vq, slot); 182 return 1; 183 } 184 185 void 186 viornd_tick(void *arg) 187 { 188 struct viornd_softc *sc = arg; 189 struct virtio_softc *vsc = sc->sc_virtio; 190 struct virtqueue *vq = &sc->sc_vq; 191 int slot; 192 193 bus_dmamap_sync(vsc->sc_dmat, sc->sc_dmamap, 0, VIORND_BUFSIZE, 194 BUS_DMASYNC_PREREAD); 195 if (virtio_enqueue_prep(vq, &slot) != 0 || 196 virtio_enqueue_reserve(vq, slot, 1) != 0) { 197 panic("%s: virtqueue enqueue failed", sc->sc_dev.dv_xname); 198 } 199 virtio_enqueue(vq, slot, sc->sc_dmamap, 0); 200 virtio_enqueue_commit(vsc, vq, slot, 1); 201 } 202