/*-
 * Copyright (c) 2017 Oliver Pinter
 * Copyright (c) 2017 W. Dean Freeman
 * Copyright (c) 2000-2015 Mark R V Murray
 * Copyright (c) 2013 Arthur Mesh
 * Copyright (c) 2004 Robert N. M. Watson
 * All rights reserved.
 *
 * 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
 *    in this position and unchanged.
 * 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 AUTHOR ``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 AUTHOR 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/param.h>
#include <sys/systm.h>
#include <sys/ck.h>
#include <sys/conf.h>
#include <sys/epoch.h>
#include <sys/eventhandler.h>
#include <sys/hash.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/linker.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/random.h>
#include <sys/sbuf.h>
#include <sys/sysctl.h>
#include <sys/unistd.h>

#include <machine/atomic.h>
#include <machine/cpu.h>

#include <crypto/rijndael/rijndael-api-fst.h>
#include <crypto/sha2/sha256.h>

#include <dev/random/fortuna.h>
#include <dev/random/hash.h>
#include <dev/random/randomdev.h>
#include <dev/random/random_harvestq.h>

#if defined(RANDOM_ENABLE_ETHER)
#define _RANDOM_HARVEST_ETHER_OFF 0
#else
#define _RANDOM_HARVEST_ETHER_OFF (1u << RANDOM_NET_ETHER)
#endif
#if defined(RANDOM_ENABLE_UMA)
#define _RANDOM_HARVEST_UMA_OFF 0
#else
#define _RANDOM_HARVEST_UMA_OFF (1u << RANDOM_UMA)
#endif

/*
 * Note that random_sources_feed() will also use this to try and split up
 * entropy into a subset of pools per iteration with the goal of feeding
 * HARVESTSIZE into every pool at least once per second.
 */
#define RANDOM_KTHREAD_HZ       10

static void random_kthread(void);
static void random_sources_feed(void);

/*
 * Random must initialize much earlier than epoch, but we can initialize the
 * epoch code before SMP starts.  Prior to SMP, we can safely bypass
 * concurrency primitives.
 */
static __read_mostly bool epoch_inited;
static __read_mostly epoch_t rs_epoch;

static const char *random_source_descr[];

/*
 * How many events to queue up. We create this many items in
 * an 'empty' queue, then transfer them to the 'harvest' queue with
 * supplied junk. When used, they are transferred back to the
 * 'empty' queue.
 */
#define RANDOM_RING_MAX         1024
#define RANDOM_ACCUM_MAX        8

/* 1 to let the kernel thread run, 0 to terminate, -1 to mark completion */
volatile int random_kthread_control;


/*
 * Allow the sysadmin to select the broad category of entropy types to harvest.
 *
 * Updates are synchronized by the harvest mutex.
 */
__read_frequently u_int hc_source_mask;
CTASSERT(ENTROPYSOURCE <= sizeof(hc_source_mask) * NBBY);

struct random_sources {
        CK_LIST_ENTRY(random_sources)    rrs_entries;
        const struct random_source      *rrs_source;
};

static CK_LIST_HEAD(sources_head, random_sources) source_list =
    CK_LIST_HEAD_INITIALIZER(source_list);

SYSCTL_NODE(_kern_random, OID_AUTO, harvest, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "Entropy Device Parameters");

/*
 * Put all the harvest queue context stuff in one place.
 * this make is a bit easier to lock and protect.
 */
static struct harvest_context {
        /* The harvest mutex protects all of harvest_context and
         * the related data.
         */
        struct mtx hc_mtx;
        /* Round-robin destination cache. */
        u_int hc_destination[ENTROPYSOURCE];
        /* The context of the kernel thread processing harvested entropy */
        struct proc *hc_kthread_proc;
        /*
         * A pair of buffers for queued events.  New events are added to the
         * active queue while the kthread processes the other one in parallel.
         */
        struct entropy_buffer {
                struct harvest_event ring[RANDOM_RING_MAX];
                u_int pos;
        } hc_entropy_buf[2];
        u_int hc_active_buf;
        struct fast_entropy_accumulator {
                volatile u_int pos;
                uint32_t buf[RANDOM_ACCUM_MAX];
        } hc_entropy_fast_accumulator;
} harvest_context;

#define RANDOM_HARVEST_INIT_LOCK()      mtx_init(&harvest_context.hc_mtx, \
                                            "entropy harvest mutex", NULL, MTX_SPIN)
#define RANDOM_HARVEST_LOCK()           mtx_lock_spin(&harvest_context.hc_mtx)
#define RANDOM_HARVEST_UNLOCK()         mtx_unlock_spin(&harvest_context.hc_mtx)

static struct kproc_desc random_proc_kp = {
        "rand_harvestq",
        random_kthread,
        &harvest_context.hc_kthread_proc,
};

/* Pass the given event straight through to Fortuna/Whatever. */
static __inline void
random_harvestq_fast_process_event(struct harvest_event *event)
{
        p_random_alg_context->ra_event_processor(event);
        explicit_bzero(event, sizeof(*event));
}

static void
random_kthread(void)
{
        struct harvest_context *hc;

        hc = &harvest_context;
        for (random_kthread_control = 1; random_kthread_control;) {
                struct entropy_buffer *buf;
                u_int entries;

                /* Deal with queued events. */
                RANDOM_HARVEST_LOCK();
                buf = &hc->hc_entropy_buf[hc->hc_active_buf];
                entries = buf->pos;
                buf->pos = 0;
                hc->hc_active_buf = (hc->hc_active_buf + 1) %
                    nitems(hc->hc_entropy_buf);
                RANDOM_HARVEST_UNLOCK();
                for (u_int i = 0; i < entries; i++)
                        random_harvestq_fast_process_event(&buf->ring[i]);

                /* Poll sources of noise. */
                random_sources_feed();

                /* XXX: FIX!! Increase the high-performance data rate? Need some measurements first. */
                for (u_int i = 0; i < RANDOM_ACCUM_MAX; i++) {
                        if (hc->hc_entropy_fast_accumulator.buf[i]) {
                                random_harvest_direct(&hc->hc_entropy_fast_accumulator.buf[i],
                                    sizeof(hc->hc_entropy_fast_accumulator.buf[0]), RANDOM_UMA);
                                hc->hc_entropy_fast_accumulator.buf[i] = 0;
                        }
                }
                /* XXX: FIX!! This is a *great* place to pass hardware/live entropy to random(9) */
                tsleep_sbt(&hc->hc_kthread_proc, 0, "-",
                    SBT_1S/RANDOM_KTHREAD_HZ, 0, C_PREL(1));
        }
        random_kthread_control = -1;
        wakeup(&hc->hc_kthread_proc);
        kproc_exit(0);
        /* NOTREACHED */
}
SYSINIT(random_device_h_proc, SI_SUB_KICK_SCHEDULER, SI_ORDER_ANY, kproc_start,
    &random_proc_kp);
_Static_assert(SI_SUB_KICK_SCHEDULER > SI_SUB_RANDOM,
    "random kthread starting before subsystem initialization");

static void
rs_epoch_init(void *dummy __unused)
{
        rs_epoch = epoch_alloc("Random Sources", EPOCH_PREEMPT);
        epoch_inited = true;
}
SYSINIT(rs_epoch_init, SI_SUB_EPOCH, SI_ORDER_ANY, rs_epoch_init, NULL);

/*
 * Run through all fast sources reading entropy for the given
 * number of rounds, which should be a multiple of the number
 * of entropy accumulation pools in use; it is 32 for Fortuna.
 */
static void
random_sources_feed(void)
{
        uint32_t entropy[HARVESTSIZE];
        struct epoch_tracker et;
        struct random_sources *rrs;
        u_int i, n, npools;
        bool rse_warm;

        rse_warm = epoch_inited;

        /*
         * Evenly-ish distribute pool population across the second based on how
         * frequently random_kthread iterates.
         *
         * For Fortuna, the math currently works out as such:
         *
         * 64 bits * 4 pools = 256 bits per iteration
         * 256 bits * 10 Hz = 2560 bits per second, 320 B/s
         *
         */
        npools = howmany(p_random_alg_context->ra_poolcount, RANDOM_KTHREAD_HZ);

        /*-
         * If we're not seeded yet, attempt to perform a "full seed", filling
         * all of the PRNG's pools with entropy; if there is enough entropy
         * available from "fast" entropy sources this will allow us to finish
         * seeding and unblock the boot process immediately rather than being
         * stuck for a few seconds with random_kthread gradually collecting a
         * small chunk of entropy every 1 / RANDOM_KTHREAD_HZ seconds.
         *
         * We collect RANDOM_FORTUNA_DEFPOOLSIZE bytes per pool, i.e. enough
         * to fill Fortuna's pools in the default configuration.  With another
         * PRNG or smaller pools for Fortuna, we might collect more entropy
         * than needed to fill the pools, but this is harmless; alternatively,
         * a different PRNG, larger pools, or fast entropy sources which are
         * not able to provide as much entropy as we request may result in the
         * not being fully seeded (and thus remaining blocked) but in that
         * case we will return here after 1 / RANDOM_KTHREAD_HZ seconds and
         * try again for a large amount of entropy.
         */
        if (!p_random_alg_context->ra_seeded())
                npools = howmany(p_random_alg_context->ra_poolcount *
                    RANDOM_FORTUNA_DEFPOOLSIZE, sizeof(entropy));

        /*
         * Step over all of live entropy sources, and feed their output
         * to the system-wide RNG.
         */
        if (rse_warm)
                epoch_enter_preempt(rs_epoch, &et);
        CK_LIST_FOREACH(rrs, &source_list, rrs_entries) {
                for (i = 0; i < npools; i++) {
                        if (rrs->rrs_source->rs_read == NULL) {
                                /* Source pushes entropy asynchronously. */
                                continue;
                        }
                        n = rrs->rrs_source->rs_read(entropy, sizeof(entropy));
                        KASSERT((n <= sizeof(entropy)),
                            ("%s: rs_read returned too much data (%u > %zu)",
                            __func__, n, sizeof(entropy)));

                        /*
                         * Sometimes the HW entropy source doesn't have anything
                         * ready for us.  This isn't necessarily untrustworthy.
                         * We don't perform any other verification of an entropy
                         * source (i.e., length is allowed to be anywhere from 1
                         * to sizeof(entropy), quality is unchecked, etc), so
                         * don't balk verbosely at slow random sources either.
                         * There are reports that RDSEED on x86 metal falls
                         * behind the rate at which we query it, for example.
                         * But it's still a better entropy source than RDRAND.
                         */
                        if (n == 0)
                                continue;
                        random_harvest_direct(entropy, n, rrs->rrs_source->rs_source);
                }
        }
        if (rse_warm)
                epoch_exit_preempt(rs_epoch, &et);
        explicit_bzero(entropy, sizeof(entropy));
}

/*
 * State used for conducting NIST SP 800-90B health tests on entropy sources.
 */
static struct health_test_softc {
        uint32_t ht_rct_value[HARVESTSIZE + 1];
        u_int ht_rct_count;     /* number of samples with the same value */
        u_int ht_rct_limit;     /* constant after init */

        uint32_t ht_apt_value[HARVESTSIZE + 1];
        u_int ht_apt_count;     /* number of samples with the same value */
        u_int ht_apt_seq;       /* sequence number of the last sample */
        u_int ht_apt_cutoff;    /* constant after init */

        uint64_t ht_total_samples;
        bool ondemand;          /* Set to true to restart the state machine */
        enum {
                INIT = 0,       /* initial state */
                DISABLED,       /* health checking is disabled */
                STARTUP,        /* doing startup tests, samples are discarded */
                STEADY,         /* steady-state operation */
                FAILED,         /* health check failed, discard samples */
        } ht_state;
} healthtest[ENTROPYSOURCE];

#define RANDOM_SELFTEST_STARTUP_SAMPLES 1024    /* 4.3, requirement 4 */
#define RANDOM_SELFTEST_APT_WINDOW      512     /* 4.4.2 */

static void
copy_event(uint32_t dst[static HARVESTSIZE + 1],
    const struct harvest_event *event)
{
        memset(dst, 0, sizeof(uint32_t) * (HARVESTSIZE + 1));
        memcpy(dst, event->he_entropy, event->he_size);
        if (event->he_source <= RANDOM_ENVIRONMENTAL_END) {
                /*
                 * For pure entropy sources the timestamp counter is generally
                 * quite determinstic since samples are taken at regular
                 * intervals, so does not contribute much to the entropy.  To
                 * make health tests more effective, exclude it from the sample,
                 * since it might otherwise defeat the health tests in a
                 * scenario where the source is stuck.
                 */
                dst[HARVESTSIZE] = event->he_somecounter;
        }
}

static void
random_healthtest_rct_init(struct health_test_softc *ht,
    const struct harvest_event *event)
{
        ht->ht_rct_count = 1;
        copy_event(ht->ht_rct_value, event);
}

/*
 * Apply the repitition count test to a sample.
 *
 * Return false if the test failed, i.e., we observed >= C consecutive samples
 * with the same value, and true otherwise.
 */
static bool
random_healthtest_rct_next(struct health_test_softc *ht,
    const struct harvest_event *event)
{
        uint32_t val[HARVESTSIZE + 1];

        copy_event(val, event);
        if (memcmp(val, ht->ht_rct_value, sizeof(ht->ht_rct_value)) != 0) {
                ht->ht_rct_count = 1;
                memcpy(ht->ht_rct_value, val, sizeof(ht->ht_rct_value));
                return (true);
        } else {
                ht->ht_rct_count++;
                return (ht->ht_rct_count < ht->ht_rct_limit);
        }
}

static void
random_healthtest_apt_init(struct health_test_softc *ht,
    const struct harvest_event *event)
{
        ht->ht_apt_count = 1;
        ht->ht_apt_seq = 1;
        copy_event(ht->ht_apt_value, event);
}

static bool
random_healthtest_apt_next(struct health_test_softc *ht,
    const struct harvest_event *event)
{
        uint32_t val[HARVESTSIZE + 1];

        if (ht->ht_apt_seq == 0) {
                random_healthtest_apt_init(ht, event);
                return (true);
        }

        copy_event(val, event);
        if (memcmp(val, ht->ht_apt_value, sizeof(ht->ht_apt_value)) == 0) {
                ht->ht_apt_count++;
                if (ht->ht_apt_count >= ht->ht_apt_cutoff)
                        return (false);
        }

        ht->ht_apt_seq++;
        if (ht->ht_apt_seq == RANDOM_SELFTEST_APT_WINDOW)
                ht->ht_apt_seq = 0;

        return (true);
}

/*
 * Run the health tests for the given event.  This is assumed to be called from
 * a serialized context.
 */
bool
random_harvest_healthtest(const struct harvest_event *event)
{
        struct health_test_softc *ht;

        ht = &healthtest[event->he_source];

        /*
         * Was on-demand testing requested?  Restart the state machine if so,
         * restarting the startup tests.
         */
        if (atomic_load_bool(&ht->ondemand)) {
                atomic_store_bool(&ht->ondemand, false);
                ht->ht_state = INIT;
        }

        switch (ht->ht_state) {
        case __predict_false(INIT):
                /* Store the first sample and initialize test state. */
                random_healthtest_rct_init(ht, event);
                random_healthtest_apt_init(ht, event);
                ht->ht_total_samples = 0;
                ht->ht_state = STARTUP;
                return (false);
        case DISABLED:
                /* No health testing for this source. */
                return (true);
        case STEADY:
        case STARTUP:
                ht->ht_total_samples++;
                if (random_healthtest_rct_next(ht, event) &&
                    random_healthtest_apt_next(ht, event)) {
                        if (ht->ht_state == STARTUP &&
                            ht->ht_total_samples >=
                            RANDOM_SELFTEST_STARTUP_SAMPLES) {
                                printf(
                            "random: health test passed for source %s\n",
                                    random_source_descr[event->he_source]);
                                ht->ht_state = STEADY;
                        }
                        return (ht->ht_state == STEADY);
                }
                ht->ht_state = FAILED;
                printf(
            "random: health test failed for source %s, discarding samples\n",
                    random_source_descr[event->he_source]);
                /* FALLTHROUGH */
        case FAILED:
                return (false);
        }
}

static bool nist_healthtest_enabled = false;
SYSCTL_BOOL(_kern_random, OID_AUTO, nist_healthtest_enabled,
    CTLFLAG_RDTUN, &nist_healthtest_enabled, 0,
    "Enable NIST SP 800-90B health tests for noise sources");

static void
random_healthtest_init(enum random_entropy_source source, int min_entropy)
{
        struct health_test_softc *ht;

        ht = &healthtest[source];
        memset(ht, 0, sizeof(*ht));
        KASSERT(ht->ht_state == INIT,
            ("%s: health test state is %d for source %d",
            __func__, ht->ht_state, source));

        /*
         * If health-testing is enabled, validate all sources except CACHED and
         * VMGENID: they are deterministic sources used only a small, fixed
         * number of times, so statistical testing is not applicable.
         */
        if (!nist_healthtest_enabled ||
            source == RANDOM_CACHED || source == RANDOM_PURE_VMGENID) {
                ht->ht_state = DISABLED;
                return;
        }

        /*
         * Set cutoff values for the two tests, given a min-entropy estimate for
         * the source and allowing for an error rate of 1 in 2^{34}.  With a
         * min-entropy estimate of 1 bit and a sample rate of RANDOM_KTHREAD_HZ,
         * we expect to see an false positive once in ~54.5 years.
         *
         * The RCT limit comes from the formula in section 4.4.1.
         *
         * The APT cutoffs are calculated using the formula in section 4.4.2
         * footnote 10 with the number of Bernoulli trials changed from W to
         * W-1, since the test as written counts the number of samples equal to
         * the first sample in the window, and thus tests W-1 samples.  We
         * provide cutoffs for estimates up to sizeof(uint32_t)*HARVESTSIZE*8
         * bits.
         */
        const int apt_cutoffs[] = {
                [1] = 329,
                [2] = 195,
                [3] = 118,
                [4] = 73,
                [5] = 48,
                [6] = 33,
                [7] = 23,
                [8] = 17,
                [9] = 13,
                [10] = 11,
                [11] = 9,
                [12] = 8,
                [13] = 7,
                [14] = 6,
                [15] = 5,
                [16] = 5,
                [17 ... 19] = 4,
                [20 ... 25] = 3,
                [26 ... 42] = 2,
                [43 ... 64] = 1,
        };
        const int error_rate = 34;

        if (min_entropy == 0) {
                /*
                 * For environmental sources, the main source of entropy is the
                 * associated timecounter value.  Since these sources can be
                 * influenced by unprivileged users, we conservatively use a
                 * min-entropy estimate of 1 bit per sample.  For "pure"
                 * sources, we assume 8 bits per sample, as such sources provide
                 * a variable amount of data per read and in particular might
                 * only provide a single byte at a time.
                 */
                min_entropy = source >= RANDOM_PURE_START ? 8 : 1;
        } else if (min_entropy < 0 || min_entropy >= nitems(apt_cutoffs)) {
                panic("invalid min_entropy %d for %s", min_entropy,
                    random_source_descr[source]);
        }

        ht->ht_rct_limit = 1 + howmany(error_rate, min_entropy);
        ht->ht_apt_cutoff = apt_cutoffs[min_entropy];
}

static int
random_healthtest_ondemand(SYSCTL_HANDLER_ARGS)
{
        u_int mask, source;
        int error;

        mask = 0;
        error = sysctl_handle_int(oidp, &mask, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);

        while (mask != 0) {
                source = ffs(mask) - 1;
                if (source < nitems(healthtest))
                        atomic_store_bool(&healthtest[source].ondemand, true);
                mask &= ~(1u << source);
        }
        return (0);
}
SYSCTL_PROC(_kern_random, OID_AUTO, nist_healthtest_ondemand,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
    random_healthtest_ondemand, "I",
    "Re-run NIST SP 800-90B startup health tests for a noise source");

static int
random_check_uint_harvestmask(SYSCTL_HANDLER_ARGS)
{
        static const u_int user_immutable_mask =
            (((1 << ENTROPYSOURCE) - 1) & (-1UL << RANDOM_PURE_START)) |
            _RANDOM_HARVEST_ETHER_OFF | _RANDOM_HARVEST_UMA_OFF;

        int error;
        u_int value;

        value = atomic_load_int(&hc_source_mask);
        error = sysctl_handle_int(oidp, &value, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);

        if (flsl(value) > ENTROPYSOURCE)
                return (EINVAL);

        /*
         * Disallow userspace modification of pure entropy sources.
         */
        RANDOM_HARVEST_LOCK();
        hc_source_mask = (value & ~user_immutable_mask) |
            (hc_source_mask & user_immutable_mask);
        RANDOM_HARVEST_UNLOCK();
        return (0);
}
SYSCTL_PROC(_kern_random_harvest, OID_AUTO, mask,
    CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
    random_check_uint_harvestmask, "IU",
    "Entropy harvesting mask");

static int
random_print_harvestmask(SYSCTL_HANDLER_ARGS)
{
        struct sbuf sbuf;
        int error, i;

        error = sysctl_wire_old_buffer(req, 0);
        if (error == 0) {
                u_int mask;

                sbuf_new_for_sysctl(&sbuf, NULL, 128, req);
                mask = atomic_load_int(&hc_source_mask);
                for (i = ENTROPYSOURCE - 1; i >= 0; i--) {
                        bool present;

                        present = (mask & (1u << i)) != 0;
                        sbuf_cat(&sbuf, present ? "1" : "0");
                }
                error = sbuf_finish(&sbuf);
                sbuf_delete(&sbuf);
        }
        return (error);
}
SYSCTL_PROC(_kern_random_harvest, OID_AUTO, mask_bin,
    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
    random_print_harvestmask, "A",
    "Entropy harvesting mask (printable)");

static const char *random_source_descr[/*ENTROPYSOURCE*/] = {
        [RANDOM_CACHED] = "CACHED",
        [RANDOM_ATTACH] = "ATTACH",
        [RANDOM_KEYBOARD] = "KEYBOARD",
        [RANDOM_MOUSE] = "MOUSE",
        [RANDOM_NET_TUN] = "NET_TUN",
        [RANDOM_NET_ETHER] = "NET_ETHER",
        [RANDOM_NET_NG] = "NET_NG",
        [RANDOM_INTERRUPT] = "INTERRUPT",
        [RANDOM_SWI] = "SWI",
        [RANDOM_FS_ATIME] = "FS_ATIME",
        [RANDOM_UMA] = "UMA",
        [RANDOM_CALLOUT] = "CALLOUT",
        [RANDOM_RANDOMDEV] = "RANDOMDEV", /* ENVIRONMENTAL_END */
        [RANDOM_PURE_TPM] = "PURE_TPM", /* PURE_START */
        [RANDOM_PURE_RDRAND] = "PURE_RDRAND",
        [RANDOM_PURE_RDSEED] = "PURE_RDSEED",
        [RANDOM_PURE_NEHEMIAH] = "PURE_NEHEMIAH",
        [RANDOM_PURE_RNDTEST] = "PURE_RNDTEST",
        [RANDOM_PURE_VIRTIO] = "PURE_VIRTIO",
        [RANDOM_PURE_BROADCOM] = "PURE_BROADCOM",
        [RANDOM_PURE_CCP] = "PURE_CCP",
        [RANDOM_PURE_DARN] = "PURE_DARN",
        [RANDOM_PURE_VMGENID] = "PURE_VMGENID",
        [RANDOM_PURE_QUALCOMM] = "PURE_QUALCOMM",
        [RANDOM_PURE_ARMV8] = "PURE_ARMV8",
        [RANDOM_PURE_ARM_TRNG] = "PURE_ARM_TRNG",
        [RANDOM_PURE_SAFE] = "PURE_SAFE",
        [RANDOM_PURE_GLXSB] = "PURE_GLXSB",
        /* "ENTROPYSOURCE" */
};
CTASSERT(nitems(random_source_descr) == ENTROPYSOURCE);

static int
random_print_harvestmask_symbolic(SYSCTL_HANDLER_ARGS)
{
        struct sbuf sbuf;
        int error, i;
        bool first;

        first = true;
        error = sysctl_wire_old_buffer(req, 0);
        if (error == 0) {
                u_int mask;

                sbuf_new_for_sysctl(&sbuf, NULL, 128, req);
                mask = atomic_load_int(&hc_source_mask);
                for (i = ENTROPYSOURCE - 1; i >= 0; i--) {
                        bool present;

                        present = (mask & (1u << i)) != 0;
                        if (i >= RANDOM_PURE_START && !present)
                                continue;
                        if (!first)
                                sbuf_cat(&sbuf, ",");
                        sbuf_cat(&sbuf, !present ? "[" : "");
                        sbuf_cat(&sbuf, random_source_descr[i]);
                        sbuf_cat(&sbuf, !present ? "]" : "");
                        first = false;
                }
                error = sbuf_finish(&sbuf);
                sbuf_delete(&sbuf);
        }
        return (error);
}
SYSCTL_PROC(_kern_random_harvest, OID_AUTO, mask_symbolic,
    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
    random_print_harvestmask_symbolic, "A",
    "Entropy harvesting mask (symbolic)");

static void
random_harvestq_init(void *unused __unused)
{
        static const u_int almost_everything_mask =
            (((1 << (RANDOM_ENVIRONMENTAL_END + 1)) - 1) &
            ~_RANDOM_HARVEST_ETHER_OFF & ~_RANDOM_HARVEST_UMA_OFF);

        hc_source_mask = almost_everything_mask;
        RANDOM_HARVEST_INIT_LOCK();
        harvest_context.hc_active_buf = 0;

        for (int i = RANDOM_START; i <= RANDOM_ENVIRONMENTAL_END; i++)
                random_healthtest_init(i, 0);
}
SYSINIT(random_device_h_init, SI_SUB_RANDOM, SI_ORDER_THIRD, random_harvestq_init, NULL);

/*
 * Subroutine to slice up a contiguous chunk of 'entropy' and feed it into the
 * underlying algorithm.  Returns number of bytes actually fed into underlying
 * algorithm.
 */
static size_t
random_early_prime(char *entropy, size_t len)
{
        struct harvest_event event;
        size_t i;

        len = rounddown(len, sizeof(event.he_entropy));
        if (len == 0)
                return (0);

        for (i = 0; i < len; i += sizeof(event.he_entropy)) {
                event.he_somecounter = random_get_cyclecount();
                event.he_size = sizeof(event.he_entropy);
                event.he_source = RANDOM_CACHED;
                event.he_destination =
                    harvest_context.hc_destination[RANDOM_CACHED]++;
                memcpy(event.he_entropy, entropy + i, sizeof(event.he_entropy));
                random_harvestq_fast_process_event(&event);
        }
        explicit_bzero(entropy, len);
        return (len);
}

/*
 * Subroutine to search for known loader-loaded files in memory and feed them
 * into the underlying algorithm early in boot.  Returns the number of bytes
 * loaded (zero if none were loaded).
 */
static size_t
random_prime_loader_file(const char *type)
{
        uint8_t *keyfile, *data;
        size_t size;

        keyfile = preload_search_by_type(type);
        if (keyfile == NULL)
                return (0);

        data = preload_fetch_addr(keyfile);
        size = preload_fetch_size(keyfile);
        if (data == NULL)
                return (0);

        return (random_early_prime(data, size));
}

/*
 * This is used to prime the RNG by grabbing any early random stuff
 * known to the kernel, and inserting it directly into the hashing
 * module, currently Fortuna.
 */
static void
random_harvestq_prime(void *unused __unused)
{
        size_t size;

        /*
         * Get entropy that may have been preloaded by loader(8)
         * and use it to pre-charge the entropy harvest queue.
         */
        size = random_prime_loader_file(RANDOM_CACHED_BOOT_ENTROPY_MODULE);
        if (bootverbose) {
                if (size > 0)
                        printf("random: read %zu bytes from preloaded cache\n",
                            size);
                else
                        printf("random: no preloaded entropy cache\n");
        }
        size = random_prime_loader_file(RANDOM_PLATFORM_BOOT_ENTROPY_MODULE);
        if (bootverbose) {
                if (size > 0)
                        printf("random: read %zu bytes from platform bootloader\n",
                            size);
                else
                        printf("random: no platform bootloader entropy\n");
        }
}
SYSINIT(random_device_prime, SI_SUB_RANDOM, SI_ORDER_MIDDLE, random_harvestq_prime, NULL);

static void
random_harvestq_deinit(void *unused __unused)
{

        /* Command the hash/reseed thread to end and wait for it to finish */
        random_kthread_control = 0;
        while (random_kthread_control >= 0)
                tsleep(&harvest_context.hc_kthread_proc, 0, "harvqterm", hz/5);
}
SYSUNINIT(random_device_h_init, SI_SUB_RANDOM, SI_ORDER_THIRD, random_harvestq_deinit, NULL);

/*-
 * Entropy harvesting queue routine.
 *
 * This is supposed to be fast; do not do anything slow in here!
 * It is also illegal (and morally reprehensible) to insert any
 * high-rate data here. "High-rate" is defined as a data source
 * that is likely to fill up the buffer in much less than 100ms.
 * This includes the "always-on" sources like the Intel "rdrand"
 * or the VIA Nehamiah "xstore" sources.
 */
/* XXXRW: get_cyclecount() is cheap on most modern hardware, where cycle
 * counters are built in, but on older hardware it will do a real time clock
 * read which can be quite expensive.
 */
void
random_harvest_queue_(const void *entropy, u_int size, enum random_entropy_source origin)
{
        struct harvest_context *hc;
        struct entropy_buffer *buf;
        struct harvest_event *event;

        KASSERT(origin >= RANDOM_START && origin < ENTROPYSOURCE,
            ("%s: origin %d invalid", __func__, origin));

        hc = &harvest_context;
        RANDOM_HARVEST_LOCK();
        buf = &hc->hc_entropy_buf[hc->hc_active_buf];
        if (buf->pos < RANDOM_RING_MAX) {
                event = &buf->ring[buf->pos++];
                event->he_somecounter = random_get_cyclecount();
                event->he_source = origin;
                event->he_destination = hc->hc_destination[origin]++;
                if (size <= sizeof(event->he_entropy)) {
                        event->he_size = size;
                        memcpy(event->he_entropy, entropy, size);
                } else {
                        /* Big event, so squash it */
                        event->he_size = sizeof(event->he_entropy[0]);
                        event->he_entropy[0] = jenkins_hash(entropy, size, (uint32_t)(uintptr_t)event);
                }
        }
        RANDOM_HARVEST_UNLOCK();
}

/*-
 * Entropy harvesting fast routine.
 *
 * This is supposed to be very fast; do not do anything slow in here!
 * This is the right place for high-rate harvested data.
 */
void
random_harvest_fast_(const void *entropy, u_int size)
{
        u_int pos;

        pos = harvest_context.hc_entropy_fast_accumulator.pos;
        harvest_context.hc_entropy_fast_accumulator.buf[pos] ^=
            jenkins_hash(entropy, size, random_get_cyclecount());
        harvest_context.hc_entropy_fast_accumulator.pos = (pos + 1)%RANDOM_ACCUM_MAX;
}

/*-
 * Entropy harvesting direct routine.
 *
 * This is not supposed to be fast, but will only be used during
 * (e.g.) booting when initial entropy is being gathered.
 */
void
random_harvest_direct_(const void *entropy, u_int size, enum random_entropy_source origin)
{
        struct harvest_event event;

        KASSERT(origin >= RANDOM_START && origin < ENTROPYSOURCE, ("%s: origin %d invalid\n", __func__, origin));
        size = MIN(size, sizeof(event.he_entropy));
        event.he_somecounter = random_get_cyclecount();
        event.he_size = size;
        event.he_source = origin;
        event.he_destination = harvest_context.hc_destination[origin]++;
        memcpy(event.he_entropy, entropy, size);
        random_harvestq_fast_process_event(&event);
}

void
random_source_register(const struct random_source *rsource)
{
        struct random_sources *rrs;

        KASSERT(rsource != NULL, ("invalid input to %s", __func__));

        rrs = malloc(sizeof(*rrs), M_ENTROPY, M_WAITOK);
        rrs->rrs_source = rsource;

        printf("random: registering fast source %s\n", rsource->rs_ident);

        random_healthtest_init(rsource->rs_source, rsource->rs_min_entropy);

        RANDOM_HARVEST_LOCK();
        hc_source_mask |= (1 << rsource->rs_source);
        CK_LIST_INSERT_HEAD(&source_list, rrs, rrs_entries);
        RANDOM_HARVEST_UNLOCK();
}

void
random_source_deregister(const struct random_source *rsource)
{
        struct random_sources *rrs = NULL;

        KASSERT(rsource != NULL, ("invalid input to %s", __func__));

        RANDOM_HARVEST_LOCK();
        hc_source_mask &= ~(1 << rsource->rs_source);
        CK_LIST_FOREACH(rrs, &source_list, rrs_entries)
                if (rrs->rrs_source == rsource) {
                        CK_LIST_REMOVE(rrs, rrs_entries);
                        break;
                }
        RANDOM_HARVEST_UNLOCK();

        if (rrs != NULL && epoch_inited)
                epoch_wait_preempt(rs_epoch);
        free(rrs, M_ENTROPY);
}

static int
random_source_handler(SYSCTL_HANDLER_ARGS)
{
        struct epoch_tracker et;
        struct random_sources *rrs;
        struct sbuf sbuf;
        int error, count;

        error = sysctl_wire_old_buffer(req, 0);
        if (error != 0)
                return (error);

        sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
        count = 0;
        epoch_enter_preempt(rs_epoch, &et);
        CK_LIST_FOREACH(rrs, &source_list, rrs_entries) {
                sbuf_cat(&sbuf, (count++ ? ",'" : "'"));
                sbuf_cat(&sbuf, rrs->rrs_source->rs_ident);
                sbuf_cat(&sbuf, "'");
        }
        epoch_exit_preempt(rs_epoch, &et);
        error = sbuf_finish(&sbuf);
        sbuf_delete(&sbuf);
        return (error);
}
SYSCTL_PROC(_kern_random, OID_AUTO, random_sources, CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
            NULL, 0, random_source_handler, "A",
            "List of active fast entropy sources.");

MODULE_VERSION(random_harvestq, 1);