FreeBSD/Linux Kernel Cross Reference
sys/dev/random/random_harvestq.c

     /*-
      * 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/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #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/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;
    
    /*
     * 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.
    */
   __read_frequently u_int hc_source_mask;
   
   struct random_sources {
           CK_LIST_ENTRY(random_sources)    rrs_entries;
           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;
           /*
            * Lockless ring buffer holding entropy events
            * If ring.in == ring.out,
            *     the buffer is empty.
            * If ring.in != ring.out,
            *     the buffer contains harvested entropy.
            * If (ring.in + 1) == ring.out (mod RANDOM_RING_MAX),
            *     the buffer is full.
            *
            * NOTE: ring.in points to the last added element,
            * and ring.out points to the last consumed element.
            *
            * The ring.in variable needs locking as there are multiple
            * sources to the ring. Only the sources may change ring.in,
            * but the consumer may examine it.
            *
            * The ring.out variable does not need locking as there is
            * only one consumer. Only the consumer may change ring.out,
            * but the sources may examine it.
            */
           struct entropy_ring {
                   struct harvest_event ring[RANDOM_RING_MAX];
                   volatile u_int in;
                   volatile u_int out;
           } hc_entropy_ring;
           struct fast_entropy_accumulator {
                   volatile u_int pos;
                   uint32_t buf[RANDOM_ACCUM_MAX];
           } hc_entropy_fast_accumulator;
   } harvest_context;
   
   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)
   {
           u_int maxloop, ring_out, i;
   
           /*
            * Locking is not needed as this is the only place we modify ring.out, and
            * we only examine ring.in without changing it. Both of these are volatile,
            * and this is a unique thread.
            */
           for (random_kthread_control = 1; random_kthread_control;) {
                   /* Deal with events, if any. Restrict the number we do in one go. */
                   maxloop = RANDOM_RING_MAX;
                   while (harvest_context.hc_entropy_ring.out != harvest_context.hc_entropy_ring.in) {
                           ring_out = (harvest_context.hc_entropy_ring.out + 1)%RANDOM_RING_MAX;
                           random_harvestq_fast_process_event(harvest_context.hc_entropy_ring.ring + ring_out);
                           harvest_context.hc_entropy_ring.out = ring_out;
                           if (!--maxloop)
                                   break;
                   }
                   random_sources_feed();
                   /* XXX: FIX!! Increase the high-performance data rate? Need some measurements first. */
                   for (i = 0; i < RANDOM_ACCUM_MAX; i++) {
                           if (harvest_context.hc_entropy_fast_accumulator.buf[i]) {
                                   random_harvest_direct(harvest_context.hc_entropy_fast_accumulator.buf + i, sizeof(harvest_context.hc_entropy_fast_accumulator.buf[0]), RANDOM_UMA);
                                   harvest_context.hc_entropy_fast_accumulator.buf[i] = 0;
                           }
                   }
                   /* XXX: FIX!! This is a *great* place to pass hardware/live entropy to random(9) */
                   tsleep_sbt(&harvest_context.hc_kthread_proc, 0, "-",
                       SBT_1S/RANDOM_KTHREAD_HZ, 0, C_PREL(1));
           }
           random_kthread_control = -1;
           wakeup(&harvest_context.hc_kthread_proc);
           kproc_exit(0);
           /* NOTREACHED */
   }
   /* This happens well after SI_SUB_RANDOM */
   SYSINIT(random_device_h_proc, SI_SUB_KICK_SCHEDULER, SI_ORDER_ANY, kproc_start,
       &random_proc_kp);
   
   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.
            *
            * The value 64 below is RANDOM_FORTUNA_DEFPOOLSIZE, i.e. chosen 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 * 64,
                       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++) {
                           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));
   }
   
   /* ARGSUSED */
   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, orig_value;
   
           orig_value = value = 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.
            */
           hc_source_mask = (value & ~user_immutable_mask) |
               (orig_value & user_immutable_mask);
           return (0);
   }
   SYSCTL_PROC(_kern_random_harvest, OID_AUTO, mask,
       CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, NULL, 0,
       random_check_uint_harvestmask, "IU",
       "Entropy harvesting mask");
   
   /* ARGSUSED */
   static int
   random_print_harvestmask(SYSCTL_HANDLER_ARGS)
   {
           struct sbuf sbuf;
           int error, i;
   
           error = sysctl_wire_old_buffer(req, 0);
           if (error == 0) {
                   sbuf_new_for_sysctl(&sbuf, NULL, 128, req);
                   for (i = ENTROPYSOURCE - 1; i >= 0; i--)
                           sbuf_cat(&sbuf, (hc_source_mask & (1 << i)) ? "1" : "");
                   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", /* ENVIRONMENTAL_END */
           [RANDOM_PURE_OCTEON] = "PURE_OCTEON", /* PURE_START */
           [RANDOM_PURE_SAFE] = "PURE_SAFE",
           [RANDOM_PURE_GLXSB] = "PURE_GLXSB",
           [RANDOM_PURE_HIFN] = "PURE_HIFN",
           [RANDOM_PURE_RDRAND] = "PURE_RDRAND",
           [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_TPM] = "PURE_TPM",
           [RANDOM_PURE_VMGENID] = "PURE_VMGENID",
           [RANDOM_PURE_QUALCOMM] = "PURE_QUALCOMM",
           /* "ENTROPYSOURCE" */
   };
   
   /* ARGSUSED */
   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) {
                   sbuf_new_for_sysctl(&sbuf, NULL, 128, req);
                   for (i = ENTROPYSOURCE - 1; i >= 0; i--) {
                           if (i >= RANDOM_PURE_START &&
                               (hc_source_mask & (1 << i)) == 0)
                                   continue;
                           if (!first)
                                   sbuf_cat(&sbuf, ",");
                           sbuf_cat(&sbuf, !(hc_source_mask & (1 << i)) ? "[" : "");
                           sbuf_cat(&sbuf, random_source_descr[i]);
                           sbuf_cat(&sbuf, !(hc_source_mask & (1 << i)) ? "]" : "");
                           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)");
   
   /* ARGSUSED */
   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_entropy_ring.in = harvest_context.hc_entropy_ring.out = 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 = (uint32_t)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.
    */
   /* ARGSUSED */
   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);
   
   /* ARGSUSED */
   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 will usually cause lots of failures of the "Lockless read"
    * check a few lines below. 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_event *event;
           u_int ring_in;
   
           KASSERT(origin >= RANDOM_START && origin < ENTROPYSOURCE, ("%s: origin %d invalid\n", __func__, origin));
           RANDOM_HARVEST_LOCK();
           ring_in = (harvest_context.hc_entropy_ring.in + 1)%RANDOM_RING_MAX;
           if (ring_in != harvest_context.hc_entropy_ring.out) {
                   /* The ring is not full */
                   event = harvest_context.hc_entropy_ring.ring + ring_in;
                   event->he_somecounter = (uint32_t)get_cyclecount();
                   event->he_source = origin;
                   event->he_destination = harvest_context.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);
                   }
                   harvest_context.hc_entropy_ring.in = ring_in;
           }
           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, (uint32_t)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 = (uint32_t)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_harvest_register_source(enum random_entropy_source source)
   {
   
           hc_source_mask |= (1 << source);
   }
   
   void
   random_harvest_deregister_source(enum random_entropy_source source)
   {
   
           hc_source_mask &= ~(1 << source);
   }
   
   void
   random_source_register(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;
   
           random_harvest_register_source(rsource->rs_source);
   
           printf("random: registering fast source %s\n", rsource->rs_ident);
   
           RANDOM_HARVEST_LOCK();
           CK_LIST_INSERT_HEAD(&source_list, rrs, rrs_entries);
           RANDOM_HARVEST_UNLOCK();
   }
   
   void
   random_source_deregister(struct random_source *rsource)
   {
           struct random_sources *rrs = NULL;
   
           KASSERT(rsource != NULL, ("invalid input to %s", __func__));
   
           random_harvest_deregister_source(rsource->rs_source);
   
           RANDOM_HARVEST_LOCK();
           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);

Cache object: 969ba23b0b807a4a0bb828232bc4d4b9