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/* $OpenBSD: viornd.c,v 1.1 2014/01/21 21:14:58 sf Exp $ */
/*
* Copyright (c) 2014 Stefan Fritsch <sf@sfritsch.de>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/timeout.h>
#include <machine/bus.h>
#include <sys/device.h>
#include <sys/pool.h>
#include <dev/rndvar.h>
#include <dev/pci/pcivar.h>
#include <dev/pci/virtioreg.h>
#include <dev/pci/virtiovar.h>
/*
* The host may not have an unlimited supply of entropy. Therefore, we must
* not blindly get as much entropy as we can. Instead, we just request
* VIORND_BUFSIZE bytes at boot and every 15 * (1 << interval_shift) seconds.
* XXX There should be an API to check if we actually need more entropy.
*
* The lowest byte in the flags is used for transport specific settings.
* Therefore we use the second byte.
*/
#define VIORND_INTERVAL_SHIFT(f) ((f >> 8) & 0xf)
#define VIORND_INTERVAL_SHIFT_DEFAULT 5
#define VIORND_ONESHOT 0x1000
#define VIORND_BUFSIZE 16
#define VIORND_DEBUG 0
struct viornd_softc {
struct device sc_dev;
struct virtio_softc *sc_virtio;
struct virtqueue sc_vq;
int *sc_buf;
bus_dmamap_t sc_dmamap;
unsigned int sc_interval;
struct timeout sc_tick;
};
int viornd_match(struct device *, void *, void *);
void viornd_attach(struct device *, struct device *, void *);
int viornd_vq_done(struct virtqueue *);
void viornd_tick(void *);
struct cfattach viornd_ca = {
sizeof(struct viornd_softc),
viornd_match,
viornd_attach,
NULL
};
struct cfdriver viornd_cd = {
NULL, "viornd", DV_DULL
};
int viornd_match(struct device *parent, void *match, void *aux)
{
struct virtio_softc *va = aux;
if (va->sc_childdevid == PCI_PRODUCT_VIRTIO_ENTROPY)
return 1;
return 0;
}
void
viornd_attach(struct device *parent, struct device *self, void *aux)
{
struct viornd_softc *sc = (struct viornd_softc *)self;
struct virtio_softc *vsc = (struct virtio_softc *)parent;
unsigned int shift;
vsc->sc_vqs = &sc->sc_vq;
vsc->sc_nvqs = 1;
vsc->sc_config_change = 0;
if (vsc->sc_child != NULL)
panic("already attached to something else");
vsc->sc_child = self;
vsc->sc_ipl = IPL_NET;
vsc->sc_intrhand = virtio_vq_intr;
sc->sc_virtio = vsc;
virtio_negotiate_features(vsc, 0, NULL);
if (sc->sc_dev.dv_cfdata->cf_flags & VIORND_ONESHOT) {
sc->sc_interval = 0;
} else {
shift = VIORND_INTERVAL_SHIFT(sc->sc_dev.dv_cfdata->cf_flags);
if (shift == 0)
shift = VIORND_INTERVAL_SHIFT_DEFAULT;
sc->sc_interval = 15 * (1 << shift);
}
#if VIORND_DEBUG
printf(": request interval: %us\n", sc->sc_interval);
#endif
sc->sc_buf = dma_alloc(VIORND_BUFSIZE, PR_NOWAIT|PR_ZERO);
if (sc->sc_buf == NULL) {
printf(": Can't alloc dma buffer\n");
goto err;
}
if (bus_dmamap_create(sc->sc_virtio->sc_dmat, VIORND_BUFSIZE, 1,
VIORND_BUFSIZE, 0, BUS_DMA_NOWAIT|BUS_DMA_ALLOCNOW,
&sc->sc_dmamap)) {
printf(": Can't alloc dmamap\n");
goto err;
}
if (bus_dmamap_load(sc->sc_virtio->sc_dmat, sc->sc_dmamap,
sc->sc_buf, VIORND_BUFSIZE, NULL, BUS_DMA_NOWAIT|BUS_DMA_READ)) {
printf(": Can't load dmamap\n");
goto err2;
}
if (virtio_alloc_vq(vsc, &sc->sc_vq, 0, VIORND_BUFSIZE, 1,
"Entropy request") != 0) {
printf(": Can't alloc virtqueue\n");
goto err2;
}
sc->sc_vq.vq_done = viornd_vq_done;
virtio_start_vq_intr(vsc, &sc->sc_vq);
timeout_set(&sc->sc_tick, viornd_tick, sc);
timeout_add(&sc->sc_tick, 1);
printf("\n");
return;
err2:
bus_dmamap_destroy(vsc->sc_dmat, sc->sc_dmamap);
err:
vsc->sc_child = VIRTIO_CHILD_ERROR;
if (sc->sc_buf != NULL) {
dma_free(sc->sc_buf, VIORND_BUFSIZE);
sc->sc_buf = NULL;
}
return;
}
int
viornd_vq_done(struct virtqueue *vq)
{
struct virtio_softc *vsc = vq->vq_owner;
struct viornd_softc *sc = (struct viornd_softc *)vsc->sc_child;
int slot, len, i;
if (virtio_dequeue(vsc, vq, &slot, &len) != 0)
return 0;
bus_dmamap_sync(vsc->sc_dmat, sc->sc_dmamap, 0, VIORND_BUFSIZE,
BUS_DMASYNC_POSTREAD);
if (len > VIORND_BUFSIZE) {
printf("%s: inconsistent descriptor length %d > %d\n",
sc->sc_dev.dv_xname, len, VIORND_BUFSIZE);
goto out;
}
#if VIORND_DEBUG
printf("%s: got %d bytes of entropy\n", __func__, len);
#endif
for (i = 0; (i + 1) * sizeof(int) <= len; i++)
add_true_randomness(sc->sc_buf[i]);
if (sc->sc_interval)
timeout_add_sec(&sc->sc_tick, sc->sc_interval);
out:
virtio_dequeue_commit(vq, slot);
return 1;
}
void
viornd_tick(void *arg)
{
struct viornd_softc *sc = arg;
struct virtio_softc *vsc = sc->sc_virtio;
struct virtqueue *vq = &sc->sc_vq;
int slot;
bus_dmamap_sync(vsc->sc_dmat, sc->sc_dmamap, 0, VIORND_BUFSIZE,
BUS_DMASYNC_PREREAD);
if (virtio_enqueue_prep(vq, &slot) != 0 ||
virtio_enqueue_reserve(vq, slot, 1) != 0) {
panic("%s: virtqueue enqueue failed", sc->sc_dev.dv_xname);
}
virtio_enqueue(vq, slot, sc->sc_dmamap, 0);
virtio_enqueue_commit(vsc, vq, slot, 1);
}
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