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[netbsd-mini2440.git] / sys / dev / rnd.c

/*      $NetBSD: rnd.c,v 1.76 2009/09/14 09:26:28 pooka Exp $   */

/*-
 * Copyright (c) 1997 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Michael Graff <explorer@flame.org>.  This code uses ideas and
 * algorithms from the Linux driver written by Ted Ts'o.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: rnd.c,v 1.76 2009/09/14 09:26:28 pooka Exp $");

#include <sys/param.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <sys/select.h>
#include <sys/poll.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/rnd.h>
#include <sys/vnode.h>
#include <sys/pool.h>
#include <sys/kauth.h>
#include <sys/once.h>

#if defined(__HAVE_CPU_COUNTER) && !defined(_RUMPKERNEL) /* XXX: bad pooka */
#include <machine/cpu_counter.h>
#endif

#ifdef RND_DEBUG
#define DPRINTF(l,x)      if (rnd_debug & (l)) printf x
int     rnd_debug = 0;
#else
#define DPRINTF(l,x)
#endif

#define RND_DEBUG_WRITE         0x0001
#define RND_DEBUG_READ          0x0002
#define RND_DEBUG_IOCTL         0x0004
#define RND_DEBUG_SNOOZE        0x0008

/*
 * list devices attached
 */
#if 0
#define RND_VERBOSE
#endif

/*
 * The size of a temporary buffer, malloc()ed when needed, and used for
 * reading and writing data.
 */
#define RND_TEMP_BUFFER_SIZE    128

/*
 * This is a little bit of state information attached to each device that we
 * collect entropy from.  This is simply a collection buffer, and when it
 * is full it will be "detached" from the source and added to the entropy
 * pool after entropy is distilled as much as possible.
 */
#define RND_SAMPLE_COUNT        64      /* collect N samples, then compress */
typedef struct _rnd_sample_t {
        SIMPLEQ_ENTRY(_rnd_sample_t) next;
        rndsource_t     *source;
        int             cursor;
        int             entropy;
        u_int32_t       ts[RND_SAMPLE_COUNT];
        u_int32_t       values[RND_SAMPLE_COUNT];
} rnd_sample_t;

/*
 * The event queue.  Fields are altered at an interrupt level.
 * All accesses must be protected with the mutex.
 */
volatile int                    rnd_timeout_pending;
SIMPLEQ_HEAD(, _rnd_sample_t)   rnd_samples;
kmutex_t                        rnd_mtx;

/*
 * our select/poll queue
 */
struct selinfo rnd_selq;

/*
 * Set when there are readers blocking on data from us
 */
#define RND_READWAITING 0x00000001
volatile u_int32_t rnd_status;

/*
 * Memory pool for sample buffers
 */
static struct pool rnd_mempool;

/*
 * Our random pool.  This is defined here rather than using the general
 * purpose one defined in rndpool.c.
 *
 * Samples are collected and queued into a separate mutex-protected queue
 * (rnd_samples, see above), and processed in a timeout routine; therefore,
 * the mutex protecting the random pool is at IPL_SOFTCLOCK() as well.
 */
rndpool_t rnd_pool;
kmutex_t  rndpool_mtx;

/*
 * This source is used to easily "remove" queue entries when the source
 * which actually generated the events is going away.
 */
static rndsource_t rnd_source_no_collect = {
        { 'N', 'o', 'C', 'o', 'l', 'l', 'e', 'c', 't', 0, 0, 0, 0, 0, 0, 0 },
        0, 0, 0, 0,
        RND_TYPE_UNKNOWN,
        (RND_FLAG_NO_COLLECT | RND_FLAG_NO_ESTIMATE | RND_TYPE_UNKNOWN),
        NULL
};

struct callout rnd_callout;

void    rndattach(int);

dev_type_open(rndopen);
dev_type_read(rndread);
dev_type_write(rndwrite);
dev_type_ioctl(rndioctl);
dev_type_poll(rndpoll);
dev_type_kqfilter(rndkqfilter);

const struct cdevsw rnd_cdevsw = {
        rndopen, nullclose, rndread, rndwrite, rndioctl,
        nostop, notty, rndpoll, nommap, rndkqfilter, D_OTHER,
};

static inline void      rnd_wakeup_readers(void);
static inline u_int32_t rnd_estimate_entropy(rndsource_t *, u_int32_t);
static inline u_int32_t rnd_counter(void);
static        void      rnd_timeout(void *);

static int              rnd_ready = 0;
static int              rnd_have_entropy = 0;

LIST_HEAD(, __rndsource_element)        rnd_sources;

/*
 * Generate a 32-bit counter.  This should be more machine dependant,
 * using cycle counters and the like when possible.
 */
static inline u_int32_t
rnd_counter(void)
{
        struct timeval tv;

#if defined(__HAVE_CPU_COUNTER) && !defined(_RUMPKERNEL) /* XXX: bad pooka */
        if (cpu_hascounter())
                return (cpu_counter32());
#endif
        if (rnd_ready) {
                microtime(&tv);
                return (tv.tv_sec * 1000000 + tv.tv_usec);
        }
        /* when called from rnd_init, its too early to call microtime safely */
        return (0);
}

/*
 * Check to see if there are readers waiting on us.  If so, kick them.
 */
static inline void
rnd_wakeup_readers(void)
{

        /*
         * If we have added new bits, and now have enough to do something,
         * wake up sleeping readers.
         */
        mutex_enter(&rndpool_mtx);
        if (rndpool_get_entropy_count(&rnd_pool) > RND_ENTROPY_THRESHOLD * 8) {
                if (rnd_status & RND_READWAITING) {
                        DPRINTF(RND_DEBUG_SNOOZE,
                            ("waking up pending readers.\n"));
                        rnd_status &= ~RND_READWAITING;
                        wakeup(&rnd_selq);
                }
                selnotify(&rnd_selq, 0, 0);

#ifdef RND_VERBOSE
                if (!rnd_have_entropy)
                        printf("rnd: have initial entropy (%u)\n",
                               rndpool_get_entropy_count(&rnd_pool));
#endif
                rnd_have_entropy = 1;
        }
        mutex_exit(&rndpool_mtx);
}

/*
 * Use the timing of the event to estimate the entropy gathered.
 * If all the differentials (first, second, and third) are non-zero, return
 * non-zero.  If any of these are zero, return zero.
 */
static inline u_int32_t
rnd_estimate_entropy(rndsource_t *rs, u_int32_t t)
{
        int32_t delta, delta2, delta3;

        /*
         * If the time counter has overflowed, calculate the real difference.
         * If it has not, it is simplier.
         */
        if (t < rs->last_time)
                delta = UINT_MAX - rs->last_time + t;
        else
                delta = rs->last_time - t;

        if (delta < 0)
                delta = -delta;

        /*
         * Calculate the second and third order differentials
         */
        delta2 = rs->last_delta - delta;
        if (delta2 < 0)
                delta2 = -delta2;

        delta3 = rs->last_delta2 - delta2;
        if (delta3 < 0)
                delta3 = -delta3;

        rs->last_time = t;
        rs->last_delta = delta;
        rs->last_delta2 = delta2;

        /*
         * If any delta is 0, we got no entropy.  If all are non-zero, we
         * might have something.
         */
        if (delta == 0 || delta2 == 0 || delta3 == 0)
                return (0);

        return (1);
}

static int
rnd_mempool_init(void)
{

        pool_init(&rnd_mempool, sizeof(rnd_sample_t), 0, 0, 0, "rndsample",
            NULL, IPL_VM);
        return 0;
}
static ONCE_DECL(rnd_mempoolinit_ctrl);

/*
 * "Attach" the random device. This is an (almost) empty stub, since
 * pseudo-devices don't get attached until after config, after the
 * entropy sources will attach. We just use the timing of this event
 * as another potential source of initial entropy.
 */
void
rndattach(int num)
{
        u_int32_t c;

        RUN_ONCE(&rnd_mempoolinit_ctrl, rnd_mempool_init);

        /* Trap unwary players who don't call rnd_init() early */
        KASSERT(rnd_ready);

        /* mix in another counter */
        c = rnd_counter();
        rndpool_add_data(&rnd_pool, &c, sizeof(u_int32_t), 1);
}

/*
 * initialize the global random pool for our use.
 * rnd_init() must be called very early on in the boot process, so
 * the pool is ready for other devices to attach as sources.
 */
void
rnd_init(void)
{
        u_int32_t c;

        if (rnd_ready)
                return;

        mutex_init(&rnd_mtx, MUTEX_DEFAULT, IPL_VM);

        callout_init(&rnd_callout, CALLOUT_MPSAFE);

        /*
         * take a counter early, hoping that there's some variance in
         * the following operations
         */
        c = rnd_counter();

        LIST_INIT(&rnd_sources);
        SIMPLEQ_INIT(&rnd_samples);
        selinit(&rnd_selq);

        rndpool_init(&rnd_pool);
        mutex_init(&rndpool_mtx, MUTEX_DEFAULT, IPL_SOFTCLOCK);

        /* Mix *something*, *anything* into the pool to help it get started.
         * However, it's not safe for rnd_counter() to call microtime() yet,
         * so on some platforms we might just end up with zeros anyway.
         * XXX more things to add would be nice.
         */
        if (c) {
                rndpool_add_data(&rnd_pool, &c, sizeof(u_int32_t), 1);
                c = rnd_counter();
                rndpool_add_data(&rnd_pool, &c, sizeof(u_int32_t), 1);
        }

        rnd_ready = 1;

#ifdef RND_VERBOSE
        printf("rnd: initialised (%u)%s", RND_POOLBITS,
               c ? " with counter\n" : "\n");
#endif
}

int
rndopen(dev_t dev, int flags, int ifmt,
    struct lwp *l)
{

        if (rnd_ready == 0)
                return (ENXIO);

        if (minor(dev) == RND_DEV_URANDOM || minor(dev) == RND_DEV_RANDOM)
                return (0);

        return (ENXIO);
}

int
rndread(dev_t dev, struct uio *uio, int ioflag)
{
        u_int8_t *bf;
        u_int32_t entcnt, mode, n, nread;
        int ret;

        DPRINTF(RND_DEBUG_READ,
            ("Random:  Read of %d requested, flags 0x%08x\n",
            uio->uio_resid, ioflag));

        if (uio->uio_resid == 0)
                return (0);

        switch (minor(dev)) {
        case RND_DEV_RANDOM:
                mode = RND_EXTRACT_GOOD;
                break;
        case RND_DEV_URANDOM:
                mode = RND_EXTRACT_ANY;
                break;
        default:
                /* Can't happen, but this is cheap */
                return (ENXIO);
        }

        ret = 0;

        bf = malloc(RND_TEMP_BUFFER_SIZE, M_TEMP, M_WAITOK);

        while (uio->uio_resid > 0) {
                n = min(RND_TEMP_BUFFER_SIZE, uio->uio_resid);

                /*
                 * Make certain there is data available.  If there
                 * is, do the I/O even if it is partial.  If not,
                 * sleep unless the user has requested non-blocking
                 * I/O.
                 */
                for (;;) {
                        /*
                         * If not requesting strong randomness, we
                         * can always read.
                         */
                        if (mode == RND_EXTRACT_ANY)
                                break;

                        /*
                         * How much entropy do we have?  If it is enough for
                         * one hash, we can read.
                         */
                        mutex_enter(&rndpool_mtx);
                        entcnt = rndpool_get_entropy_count(&rnd_pool);
                        mutex_exit(&rndpool_mtx);
                        if (entcnt >= RND_ENTROPY_THRESHOLD * 8)
                                break;

                        /*
                         * Data is not available.
                         */
                        if (ioflag & IO_NDELAY) {
                                ret = EWOULDBLOCK;
                                goto out;
                        }

                        rnd_status |= RND_READWAITING;
                        ret = tsleep(&rnd_selq, PRIBIO|PCATCH,
                            "rndread", 0);

                        if (ret)
                                goto out;
                }

                nread = rnd_extract_data(bf, n, mode);

                /*
                 * Copy (possibly partial) data to the user.
                 * If an error occurs, or this is a partial
                 * read, bail out.
                 */
                ret = uiomove((void *)bf, nread, uio);
                if (ret != 0 || nread != n)
                        goto out;
        }

out:
        free(bf, M_TEMP);
        return (ret);
}

int
rndwrite(dev_t dev, struct uio *uio, int ioflag)
{
        u_int8_t *bf;
        int n, ret;

        DPRINTF(RND_DEBUG_WRITE,
            ("Random: Write of %d requested\n", uio->uio_resid));

        if (uio->uio_resid == 0)
                return (0);

        ret = 0;

        bf = malloc(RND_TEMP_BUFFER_SIZE, M_TEMP, M_WAITOK);

        while (uio->uio_resid > 0) {
                n = min(RND_TEMP_BUFFER_SIZE, uio->uio_resid);

                ret = uiomove((void *)bf, n, uio);
                if (ret != 0)
                        break;

                /*
                 * Mix in the bytes.
                 */
                mutex_enter(&rndpool_mtx);
                rndpool_add_data(&rnd_pool, bf, n, 0);
                mutex_exit(&rndpool_mtx);

                DPRINTF(RND_DEBUG_WRITE, ("Random: Copied in %d bytes\n", n));
        }

        free(bf, M_TEMP);
        return (ret);
}

int
rndioctl(dev_t dev, u_long cmd, void *addr, int flag,
    struct lwp *l)
{
        rndsource_element_t *rse;
        rndstat_t *rst;
        rndstat_name_t *rstnm;
        rndctl_t *rctl;
        rnddata_t *rnddata;
        u_int32_t count, start;
        int ret;

        ret = 0;

        switch (cmd) {
        case FIONBIO:
        case FIOASYNC:
        case RNDGETENTCNT:
                break;

        case RNDGETPOOLSTAT:
        case RNDGETSRCNUM:
        case RNDGETSRCNAME:
                ret = kauth_authorize_device(l->l_cred,
                    KAUTH_DEVICE_RND_GETPRIV, NULL, NULL, NULL, NULL);
                if (ret)
                        return (ret);
                break;

        case RNDCTL:
                ret = kauth_authorize_device(l->l_cred,
                    KAUTH_DEVICE_RND_SETPRIV, NULL, NULL, NULL, NULL);
                if (ret)
                        return (ret);
                break;

        case RNDADDDATA:
                ret = kauth_authorize_device(l->l_cred,
                    KAUTH_DEVICE_RND_ADDDATA, NULL, NULL, NULL, NULL);
                if (ret)
                        return (ret);
                break;

        default:
                return (EINVAL);
        }

        switch (cmd) {

        /*
         * Handled in upper layer really, but we have to return zero
         * for it to be accepted by the upper layer.
         */
        case FIONBIO:
        case FIOASYNC:
                break;

        case RNDGETENTCNT:
                mutex_enter(&rndpool_mtx);
                *(u_int32_t *)addr = rndpool_get_entropy_count(&rnd_pool);
                mutex_exit(&rndpool_mtx);
                break;

        case RNDGETPOOLSTAT:
                mutex_enter(&rndpool_mtx);
                rndpool_get_stats(&rnd_pool, addr, sizeof(rndpoolstat_t));
                mutex_exit(&rndpool_mtx);
                break;

        case RNDGETSRCNUM:
                rst = (rndstat_t *)addr;

                if (rst->count == 0)
                        break;

                if (rst->count > RND_MAXSTATCOUNT)
                        return (EINVAL);

                /*
                 * Find the starting source by running through the
                 * list of sources.
                 */
                rse = rnd_sources.lh_first;
                start = rst->start;
                while (rse != NULL && start >= 1) {
                        rse = rse->list.le_next;
                        start--;
                }

                /*
                 * Return up to as many structures as the user asked
                 * for.  If we run out of sources, a count of zero
                 * will be returned, without an error.
                 */
                for (count = 0; count < rst->count && rse != NULL; count++) {
                        memcpy(&rst->source[count], &rse->data,
                            sizeof(rndsource_t));
                        /* Zero out information which may leak */
                        rst->source[count].last_time = 0;
                        rst->source[count].last_delta = 0;
                        rst->source[count].last_delta2 = 0;
                        rst->source[count].state = 0;
                        rse = rse->list.le_next;
                }

                rst->count = count;

                break;

        case RNDGETSRCNAME:
                /*
                 * Scan through the list, trying to find the name.
                 */
                rstnm = (rndstat_name_t *)addr;
                rse = rnd_sources.lh_first;
                while (rse != NULL) {
                        if (strncmp(rse->data.name, rstnm->name, 16) == 0) {
                                memcpy(&rstnm->source, &rse->data,
                                    sizeof(rndsource_t));

                                return (0);
                        }
                        rse = rse->list.le_next;
                }

                ret = ENOENT;           /* name not found */

                break;

        case RNDCTL:
                /*
                 * Set flags to enable/disable entropy counting and/or
                 * collection.
                 */
                rctl = (rndctl_t *)addr;
                rse = rnd_sources.lh_first;

                /*
                 * Flags set apply to all sources of this type.
                 */
                if (rctl->type != 0xff) {
                        while (rse != NULL) {
                                if (rse->data.type == rctl->type) {
                                        rse->data.flags &= ~rctl->mask;
                                        rse->data.flags |=
                                            (rctl->flags & rctl->mask);
                                }
                                rse = rse->list.le_next;
                        }

                        return (0);
                }

                /*
                 * scan through the list, trying to find the name
                 */
                while (rse != NULL) {
                        if (strncmp(rse->data.name, rctl->name, 16) == 0) {
                                rse->data.flags &= ~rctl->mask;
                                rse->data.flags |= (rctl->flags & rctl->mask);

                                return (0);
                        }
                        rse = rse->list.le_next;
                }

                ret = ENOENT;           /* name not found */

                break;

        case RNDADDDATA:
                rnddata = (rnddata_t *)addr;

                mutex_enter(&rndpool_mtx);
                rndpool_add_data(&rnd_pool, rnddata->data, rnddata->len,
                    rnddata->entropy);
                mutex_exit(&rndpool_mtx);

                rnd_wakeup_readers();

                break;

        default:
                return (EINVAL);
        }

        return (ret);
}

int
rndpoll(dev_t dev, int events, struct lwp *l)
{
        u_int32_t entcnt;
        int revents;

        /*
         * We are always writable.
         */
        revents = events & (POLLOUT | POLLWRNORM);

        /*
         * Save some work if not checking for reads.
         */
        if ((events & (POLLIN | POLLRDNORM)) == 0)
                return (revents);

        /*
         * If the minor device is not /dev/random, we are always readable.
         */
        if (minor(dev) != RND_DEV_RANDOM) {
                revents |= events & (POLLIN | POLLRDNORM);
                return (revents);
        }

        /*
         * Make certain we have enough entropy to be readable.
         */
        mutex_enter(&rndpool_mtx);
        entcnt = rndpool_get_entropy_count(&rnd_pool);
        mutex_exit(&rndpool_mtx);

        if (entcnt >= RND_ENTROPY_THRESHOLD * 8)
                revents |= events & (POLLIN | POLLRDNORM);
        else
                selrecord(l, &rnd_selq);

        return (revents);
}

static void
filt_rnddetach(struct knote *kn)
{
        mutex_enter(&rndpool_mtx);
        SLIST_REMOVE(&rnd_selq.sel_klist, kn, knote, kn_selnext);
        mutex_exit(&rndpool_mtx);
}

static int
filt_rndread(struct knote *kn, long hint)
{
        uint32_t entcnt;

        entcnt = rndpool_get_entropy_count(&rnd_pool);
        if (entcnt >= RND_ENTROPY_THRESHOLD * 8) {
                kn->kn_data = RND_TEMP_BUFFER_SIZE;
                return (1);
        }
        return (0);
}

static const struct filterops rnd_seltrue_filtops =
        { 1, NULL, filt_rnddetach, filt_seltrue };

static const struct filterops rndread_filtops =
        { 1, NULL, filt_rnddetach, filt_rndread };

int
rndkqfilter(dev_t dev, struct knote *kn)
{
        struct klist *klist;

        switch (kn->kn_filter) {
        case EVFILT_READ:
                klist = &rnd_selq.sel_klist;
                if (minor(dev) == RND_DEV_URANDOM)
                        kn->kn_fop = &rnd_seltrue_filtops;
                else
                        kn->kn_fop = &rndread_filtops;
                break;

        case EVFILT_WRITE:
                klist = &rnd_selq.sel_klist;
                kn->kn_fop = &rnd_seltrue_filtops;
                break;

        default:
                return (EINVAL);
        }

        kn->kn_hook = NULL;

        mutex_enter(&rndpool_mtx);
        SLIST_INSERT_HEAD(klist, kn, kn_selnext);
        mutex_exit(&rndpool_mtx);

        return (0);
}

static rnd_sample_t *
rnd_sample_allocate(rndsource_t *source)
{
        rnd_sample_t *c;

        c = pool_get(&rnd_mempool, PR_WAITOK);
        if (c == NULL)
                return (NULL);

        c->source = source;
        c->cursor = 0;
        c->entropy = 0;

        return (c);
}

/*
 * Don't wait on allocation.  To be used in an interrupt context.
 */
static rnd_sample_t *
rnd_sample_allocate_isr(rndsource_t *source)
{
        rnd_sample_t *c;

        c = pool_get(&rnd_mempool, PR_NOWAIT);
        if (c == NULL)
                return (NULL);

        c->source = source;
        c->cursor = 0;
        c->entropy = 0;

        return (c);
}

static void
rnd_sample_free(rnd_sample_t *c)
{
        memset(c, 0, sizeof(rnd_sample_t));
        pool_put(&rnd_mempool, c);
}

/*
 * Add a source to our list of sources.
 */
void
rnd_attach_source(rndsource_element_t *rs, const char *name, u_int32_t type,
    u_int32_t flags)
{
        u_int32_t ts;

        RUN_ONCE(&rnd_mempoolinit_ctrl, rnd_mempool_init);

        ts = rnd_counter();

        strlcpy(rs->data.name, name, sizeof(rs->data.name));
        rs->data.last_time = ts;
        rs->data.last_delta = 0;
        rs->data.last_delta2 = 0;
        rs->data.total = 0;

        /*
         * Force network devices to not collect any entropy by
         * default.
         */
        if (type == RND_TYPE_NET)
                flags |= (RND_FLAG_NO_COLLECT | RND_FLAG_NO_ESTIMATE);

        rs->data.type = type;
        rs->data.flags = flags;

        rs->data.state = rnd_sample_allocate(&rs->data);

        LIST_INSERT_HEAD(&rnd_sources, rs, list);

#ifdef RND_VERBOSE
        printf("rnd: %s attached as an entropy source (", rs->data.name);
        if (!(flags & RND_FLAG_NO_COLLECT)) {
                printf("collecting");
                if (flags & RND_FLAG_NO_ESTIMATE)
                        printf(" without estimation");
        }
        else
                printf("off");
        printf(")\n");
#endif

        /*
         * Again, put some more initial junk in the pool.
         * XXX Bogus, but harder to guess than zeros.
         */
        rndpool_add_data(&rnd_pool, &ts, sizeof(u_int32_t), 1);
}

/*
 * Remove a source from our list of sources.
 */
void
rnd_detach_source(rndsource_element_t *rs)
{
        rnd_sample_t *sample;
        rndsource_t *source;

        mutex_enter(&rnd_mtx);

        LIST_REMOVE(rs, list);

        source = &rs->data;

        if (source->state) {
                rnd_sample_free(source->state);
                source->state = NULL;
        }

        /*
         * If there are samples queued up "remove" them from the sample queue
         * by setting the source to the no-collect pseudosource.
         */
        sample = SIMPLEQ_FIRST(&rnd_samples);
        while (sample != NULL) {
                if (sample->source == source)
                        sample->source = &rnd_source_no_collect;

                sample = SIMPLEQ_NEXT(sample, next);
        }

        mutex_exit(&rnd_mtx);
#ifdef RND_VERBOSE
        printf("rnd: %s detached as an entropy source\n", rs->data.name);
#endif
}

/*
 * Add a value to the entropy pool. The rs parameter should point to the
 * source-specific source structure.
 */
void
rnd_add_uint32(rndsource_element_t *rs, u_int32_t val)
{
        rndsource_t *rst;
        rnd_sample_t *state;
        u_int32_t ts;


        rst = &rs->data;

        if (rst->flags & RND_FLAG_NO_COLLECT)
                return;

        /*
         * Sample the counter as soon as possible to avoid
         * entropy overestimation.
         */
        ts = rnd_counter();

        /*
         * If the sample buffer is NULL, try to allocate one here.  If this
         * fails, drop this sample.
         */
        state = rst->state;
        if (state == NULL) {
                state = rnd_sample_allocate_isr(rst);
                if (state == NULL)
                        return;
                rst->state = state;
        }

        /*
         * If we are estimating entropy on this source,
         * calculate differentials.
         */

        if ((rst->flags & RND_FLAG_NO_ESTIMATE) == 0)
                state->entropy += rnd_estimate_entropy(rst, ts);

        state->ts[state->cursor] = ts;
        state->values[state->cursor] = val;
        state->cursor++;

        /*
         * If the state arrays are not full, we're done.
         */
        if (state->cursor < RND_SAMPLE_COUNT)
                return;

        /*
         * State arrays are full.  Queue this chunk on the processing queue.
         */
        mutex_enter(&rnd_mtx);
        SIMPLEQ_INSERT_HEAD(&rnd_samples, state, next);
        rst->state = NULL;

        /*
         * If the timeout isn't pending, have it run in the near future.
         */
        if (rnd_timeout_pending == 0) {
                rnd_timeout_pending = 1;
                callout_reset(&rnd_callout, 1, rnd_timeout, NULL);
        }
        mutex_exit(&rnd_mtx);

        /*
         * To get here we have to have queued the state up, and therefore
         * we need a new state buffer.  If we can, allocate one now;
         * if we don't get it, it doesn't matter; we'll try again on
         * the next random event.
         */
        rst->state = rnd_sample_allocate_isr(rst);
}

void
rnd_add_data(rndsource_element_t *rs, void *data, u_int32_t len,
    u_int32_t entropy)
{
        rndsource_t *rst;

        /* Mix in the random data directly into the pool. */
        rndpool_add_data(&rnd_pool, data, len, entropy);

        if (rs != NULL) {
                rst = &rs->data;
                rst->total += entropy;

                if ((rst->flags & RND_FLAG_NO_ESTIMATE) == 0)
                        /* Estimate entropy using timing information */
                        rnd_add_uint32(rs, *(u_int8_t *)data);
        }

        /* Wake up any potential readers since we've just added some data. */
        rnd_wakeup_readers();
}

/*
 * Timeout, run to process the events in the ring buffer. 
 */
static void
rnd_timeout(void *arg)
{
        rnd_sample_t *sample;
        rndsource_t *source;
        u_int32_t entropy;

        /*
         * Sample queue is protected by rnd_mtx, take it briefly to dequeue.
         */
        mutex_enter(&rnd_mtx);
        rnd_timeout_pending = 0;

        sample = SIMPLEQ_FIRST(&rnd_samples);
        while (sample != NULL) {
                SIMPLEQ_REMOVE_HEAD(&rnd_samples, next);
                mutex_exit(&rnd_mtx);

                source = sample->source;

                /*
                 * We repeat this check here, since it is possible the source
                 * was disabled before we were called, but after the entry
                 * was queued.
                 */
                if ((source->flags & RND_FLAG_NO_COLLECT) == 0) {
                        entropy = sample->entropy;
                        if (source->flags & RND_FLAG_NO_ESTIMATE)
                                entropy = 0;

                        mutex_enter(&rndpool_mtx);
                        rndpool_add_data(&rnd_pool, sample->values,
                            RND_SAMPLE_COUNT * 4, 0);

                        rndpool_add_data(&rnd_pool, sample->ts,
                            RND_SAMPLE_COUNT * 4,
                            entropy);
                        mutex_exit(&rndpool_mtx);

                        source->total += sample->entropy;
                }

                rnd_sample_free(sample);

                /* Get mtx back to dequeue the next one.. */
                mutex_enter(&rnd_mtx);
                sample = SIMPLEQ_FIRST(&rnd_samples);
        }
        mutex_exit(&rnd_mtx);

        /*
         * Wake up any potential readers waiting.
         */
        rnd_wakeup_readers();
}

u_int32_t
rnd_extract_data(void *p, u_int32_t len, u_int32_t flags)
{
        int retval;
        u_int32_t c;

        mutex_enter(&rndpool_mtx);
        if (!rnd_have_entropy) {
#ifdef RND_VERBOSE
                printf("rnd: WARNING! initial entropy low (%u).\n",
                       rndpool_get_entropy_count(&rnd_pool));
#endif
                /* Try once again to put something in the pool */
                c = rnd_counter();
                rndpool_add_data(&rnd_pool, &c, sizeof(u_int32_t), 1);
        }
        retval = rndpool_extract_data(&rnd_pool, p, len, flags);
        mutex_exit(&rndpool_mtx);

        return (retval);
}