2 * Copyright (c) 2004-2014 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 * by Alex Hornung <alex@alexhornung.com>
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions, and the following disclaimer,
14 * without modification, immediately at the beginning of the file.
15 * 2. The name of the author may not be used to endorse or promote products
16 * derived from this software without specific prior written permission.
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
22 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * Note: The word "entropy" is often incorrectly used to describe
33 * random data. The word "entropy" originates from the science of
34 * Physics. The correct descriptive definition would be something
35 * along the lines of "seed", "unpredictable numbers" or
36 * "unpredictable data".
38 * Note: Some /dev/[u]random implementations save "seed" between
39 * boots which represents a security hazard since an adversary
40 * could acquire this data (since it is stored in a file). If
41 * the unpredictable data used in the above routines is only
42 * generated during Kernel operation, then an adversary can only
43 * acquire that data through a Kernel security compromise and/or
44 * a cryptographic algorithm failure/cryptanalysis.
46 * Note: On FreeBSD-4.11, interrupts have to be manually enabled
47 * using the rndcontrol(8) command.
49 * --- DESIGN (FreeBSD-4.11 based) ---
51 * The rnddev module automatically initializes itself the first time
52 * it is used (client calls any public rnddev_*() interface routine).
53 * Both CSPRNGs are initially seeded from the precise nano[up]time() routines.
54 * Tests show this method produces good enough results, suitable for intended
55 * use. It is necessary for both CSPRNGs to be completely seeded, initially.
57 * After initialization and during Kernel operation the only suitable
58 * unpredictable data available is:
60 * (1) Keyboard scan-codes.
61 * (2) Nanouptime acquired by a Keyboard/Read-Event.
62 * (3) Suitable interrupt source; hard-disk/ATA-device.
64 * (X) Mouse-event (xyz-data unsuitable); NOT IMPLEMENTED.
66 * This data is added to both CSPRNGs in real-time as it happens/
67 * becomes-available. Additionally, unpredictable (?) data may be
68 * acquired from a true-random number generator if such a device is
69 * available to the system (not advisable !).
70 * Nanouptime() acquired by a Read-Event is a very important aspect of
71 * this design, since it ensures that unpredictable data is added to
72 * the CSPRNGs even if there are no other sources.
73 * The nanouptime() Kernel routine is used since time relative to
74 * boot is less adversary-known than time itself.
76 * This design has been thoroughly tested with debug logging
77 * and the output from both /dev/random and /dev/urandom has
78 * been tested with the DIEHARD test-suite; both pass.
80 * MODIFICATIONS MADE TO ORIGINAL "kern_random.c":
84 * o Changed ReadSeed() function to schedule future read-seed-events
85 * by at least one second. Previous implementation used a randomised
86 * scheduling { 0, 1, 2, 3 seconds }.
87 * o Changed SEED_NANOUP() function to use a "previous" accumulator
88 * algorithm similar to ReadSeed(). This ensures that there is no
89 * way that an adversary can tell what number is being added to the
90 * CSPRNGs, since the number added to the CSPRNGs at Event-Time is
91 * the sum of nanouptime()@Event and an unknown/secret number.
92 * o Changed rnddev_add_interrupt() function to schedule future
93 * interrupt-events by at least one second. Previous implementation
94 * had no scheduling algorithm which allowed an "interrupt storm"
95 * to occur resulting in skewed data entering into the CSPRNGs.
100 * o Some small cleanups and change all internal functions to be
102 * o Removed ReadSeed() since its functionality is already performed
103 * by another function { rnddev_add_interrupt_OR_read() } and remove
104 * the silly rndByte accumulator/feedback-thing (since multipying by
105 * rndByte could yield a value of 0).
106 * o Made IBAA/L14 public interface become static/private;
107 * Local to this file (not changed to that in the original C modules).
111 * o SEED_NANOUP() -> NANOUP_EVENT() function rename.
112 * o Make NANOUP_EVENT() handle the time-buffering directly so that all
113 * time-stamp-events use this single time-buffer (including keyboard).
114 * This removes dependancy on "time_second" Kernel variable.
115 * o Removed second-time-buffer code in rnddev_add_interrupt_OR_read (void).
116 * o Rewrote the time-buffering algorithm in NANOUP_EVENT() to use a
117 * randomised time-delay range.
121 * o Updated to (hopefully final) L15 algorithm.
125 * o Added missing (u_char *) cast in RnddevRead() function.
126 * o Changed copyright to 3-clause BSD license and cleaned up the layout
129 * For a proper changelog, refer to the version control history of this
134 * o Made the random number generator per-cpu.
136 * o Certain entropy sources, such as RDRAND, are per-cpu.
138 * o Fixed sources such as entropy saved across reboots is split across
139 * available cpus. Interrupt and generic sources are dribbled across
142 * o In addition, we chain random generator data into the buffer randomness
143 * from cpu to cpu to force the cpus to diverge quickly from initial states.
144 * This ensures that no cpu is starved. This is done at early-init and also
145 * at regular intervals by rand_thread_loop().
147 * The chaining forces the cpus to diverge quickly and also ensures that
148 * all entropy data ultimately affects all cpus regardless of which cpu
149 * the entropy was injected into. The combination should be pretty killer.
152 #include <sys/types.h>
153 #include <sys/kernel.h>
154 #include <sys/systm.h>
155 #include <sys/poll.h>
156 #include <sys/event.h>
157 #include <sys/random.h>
158 #include <sys/systimer.h>
159 #include <sys/time.h>
160 #include <sys/proc.h>
161 #include <sys/lock.h>
162 #include <sys/sysctl.h>
163 #include <sys/sysproto.h>
164 #include <sys/spinlock.h>
165 #include <sys/csprng.h>
166 #include <sys/malloc.h>
167 #include <machine/atomic.h>
168 #include <machine/clock.h>
170 #include <sys/spinlock2.h>
171 #include <sys/signal2.h>
173 static struct csprng_state *csprng_pcpu;
174 static struct csprng_state csprng_boot;
176 static MALLOC_DEFINE(M_NRANDOM, "nrandom", "csprng");
178 static int add_buffer_randomness_state(struct csprng_state *state,
179 const char *buf, int bytes, int srcid);
182 struct csprng_state *
183 iterate_csprng_state(int bytes __unused)
185 static unsigned int csprng_iterator;
189 n = csprng_iterator++ % ncpus;
190 return &csprng_pcpu[n];
196 * Portability note: The u_char/unsigned char type is used where
197 * uint8_t from <stdint.h> or u_int8_t from <sys/types.h> should really
198 * be being used. On FreeBSD, it is safe to make the assumption that these
199 * different types are equivalent (on all architectures).
200 * The FreeBSD <sys/crypto/rc4> module also makes this assumption.
203 /*------------------------------ IBAA ----------------------------------*/
205 /*-------------------------- IBAA CSPRNG -------------------------------*/
208 * NOTE: The original source code from which this source code (IBAA)
209 * was taken has no copyright/license. The algorithm has no patent
210 * and is freely/publicly available from:
212 * http://www.burtleburtle.net/bob/rand/isaac.html
215 typedef u_int32_t u4; /* unsigned four bytes, 32 bits */
219 u4 *m, /* Memory: array of SIZE ALPHA-bit terms */
220 u4 *r, /* Results: the sequence, same size as m */
221 u4 *aa, /* Accumulator: a single value */
222 u4 *bb, /* the previous result */
223 u4 *counter /* counter */
231 for (i = 0; i < SIZE; ++i) {
233 a = barrel(a) + m[ind(i + (SIZE / 2))]; /* set a */
234 m[i] = y = m[ind(x)] + a + b; /* set m */
235 r[i] = b = m[ind(y >> ALPHA)] + x; /* set r */
240 /*-------------------------- IBAA CSPRNG -------------------------------*/
242 static void IBAA_Init(struct ibaa_state *ibaa);
243 static void IBAA_Call(struct ibaa_state *ibaa);
244 static void IBAA_Seed(struct ibaa_state *ibaa, u_int32_t val);
245 static u_char IBAA_Byte(struct ibaa_state *ibaa);
251 IBAA_Init(struct ibaa_state *ibaa)
255 for (i = 0; i < SIZE; ++i) {
256 ibaa->IBAA_memory[i] = i;
261 ibaa->IBAA_counter = 0;
262 /* force IBAA_Call() */
263 ibaa->IBAA_byte_index = sizeof(ibaa->IBAA_results);
267 * PRIVATE: Call IBAA to produce 256 32-bit u4 results.
270 IBAA_Call (struct ibaa_state *ibaa)
272 IBAA(ibaa->IBAA_memory, ibaa->IBAA_results,
273 &ibaa->IBAA_aa, &ibaa->IBAA_bb,
274 &ibaa->IBAA_counter);
275 ibaa->IBAA_byte_index = 0;
279 * Add a 32-bit u4 seed value into IBAAs memory. Mix the low 4 bits
280 * with 4 bits of PNG data to reduce the possibility of a seeding-based
284 IBAA_Seed (struct ibaa_state *ibaa, const u_int32_t val)
288 iptr = &ibaa->IBAA_memory[ibaa->memIndex & MASK];
289 *iptr = ((*iptr << 3) | (*iptr >> 29)) + (val ^ (IBAA_Byte(ibaa) & 15));
294 IBAA_Vector (struct ibaa_state *ibaa, const char *buf, int bytes)
298 while (bytes >= sizeof(int)) {
299 IBAA_Seed(ibaa, *(const int *)buf);
301 bytes -= sizeof(int);
305 * Warm up the generator to get rid of weak initial states.
307 for (i = 0; i < 10; ++i)
312 * Extract a byte from IBAAs 256 32-bit u4 results array.
314 * NOTE: This code is designed to prevent MP races from taking
315 * IBAA_byte_index out of bounds.
318 IBAA_Byte(struct ibaa_state *ibaa)
323 index = ibaa->IBAA_byte_index;
324 if (index == sizeof(ibaa->IBAA_results)) {
328 result = ((u_char *)ibaa->IBAA_results)[index];
329 ibaa->IBAA_byte_index = index + 1;
334 /*------------------------------ IBAA ----------------------------------*/
337 /*------------------------------- L15 ----------------------------------*/
340 * IMPORTANT NOTE: LByteType must be exactly 8-bits in size or this software
341 * will not function correctly.
343 typedef unsigned char LByteType;
349 static void L15_Swap(struct l15_state *l15,const LByteType pos1, const LByteType pos2);
350 static void L15_InitState(struct l15_state *l15);
351 static void L15_KSA(struct l15_state *l15,
352 const LByteType * const key,
353 const size_t keyLen);
354 static void L15_Discard(struct l15_state *l15,
355 const LByteType numCalls);
360 static void L15_Init(struct l15_state *l15,
361 const LByteType * const key,
362 const size_t keyLen);
363 static LByteType L15_Byte(struct l15_state *l15);
364 static void L15_Vector(struct l15_state *l15,
365 const LByteType * const key,
366 const size_t keyLen);
369 L15_Swap(struct l15_state *l15, const LByteType pos1, const LByteType pos2)
373 save1 = l15->L15_state[pos1];
374 l15->L15_state[pos1] = l15->L15_state[pos2];
375 l15->L15_state[pos2] = save1;
379 L15_InitState (struct l15_state *l15)
383 for (i = 0; i < L15_STATE_SIZE; ++i)
384 l15->L15_state[i] = i;
387 #define L_SCHEDULE(xx) \
389 for (i = 0; i < L15_STATE_SIZE; ++i) { \
390 L15_Swap(l15, i, (l15->stateIndex += (l15->L15_state[i] + (xx)))); \
394 L15_KSA (struct l15_state *l15, const LByteType * const key,
399 for (keyIndex = 0; keyIndex < keyLen; ++keyIndex) {
400 L_SCHEDULE(key[keyIndex]);
406 L15_Discard(struct l15_state *l15, const LByteType numCalls)
409 for (i = 0; i < numCalls; ++i) {
419 L15_Init(struct l15_state *l15, const LByteType *key,
424 l15->L15_start_x = 0;
425 l15->L15_y = L15_STATE_SIZE - 1;
427 L15_KSA(l15, key, keyLen);
428 L15_Discard(l15, L15_Byte(l15));
432 L15_Byte(struct l15_state *l15)
436 L15_Swap(l15, l15->L15_state[l15->L15_x], l15->L15_y);
437 z = (l15->L15_state [l15->L15_x++] + l15->L15_state[l15->L15_y--]);
438 if (l15->L15_x == l15->L15_start_x) {
441 return (l15->L15_state[z]);
445 L15_Vector(struct l15_state *l15, const LByteType * const key,
448 L15_KSA(l15, key, keyLen);
451 /*------------------------------- L15 ----------------------------------*/
453 /************************************************************************
455 ************************************************************************
457 * By Robin J Carey, Matthew Dillon and Alex Hornung.
460 static int rand_thread_value;
461 static void NANOUP_EVENT(struct timespec *last, struct csprng_state *state);
462 static thread_t rand_td;
464 static int sysctl_kern_random(SYSCTL_HANDLER_ARGS);
466 static int rand_mode = 2;
467 static struct systimer systimer_rand;
469 static int sysctl_kern_rand_mode(SYSCTL_HANDLER_ARGS);
471 SYSCTL_PROC(_kern, OID_AUTO, random, CTLFLAG_RD | CTLFLAG_ANYBODY, 0, 0,
472 sysctl_kern_random, "I", "Acquire random data");
473 SYSCTL_PROC(_kern, OID_AUTO, rand_mode, CTLTYPE_STRING | CTLFLAG_RW, NULL, 0,
474 sysctl_kern_rand_mode, "A", "RNG mode (csprng, ibaa or mixed)");
478 * Called twice. Once very early on when ncpus is still 1 (before
479 * kmalloc or much of anything else is available), and then again later
480 * after SMP has been heated up.
482 * The early initialization is needed so various subsystems early in the
483 * boot have some source of pseudo random bytes.
486 rand_initialize(void)
488 struct csprng_state *state;
496 csprng_pcpu = &csprng_boot;
498 csprng_pcpu = kmalloc(ncpus * sizeof(*csprng_pcpu),
499 M_NRANDOM, M_WAITOK | M_ZERO);
502 for (n = 0; n < ncpus; ++n) {
503 state = &csprng_pcpu[n];
504 rgd = globaldata_find(n);
509 /* Initialize IBAA. */
510 IBAA_Init(&state->ibaa);
512 /* Initialize L15. */
514 L15_Init(&state->l15,
515 (const LByteType *)&now.tv_nsec, sizeof(now.tv_nsec));
517 for (i = 0; i < (SIZE / 2); ++i) {
519 state->inject_counter[RAND_SRC_TIMING] = 0;
520 add_buffer_randomness_state(state,
521 (const uint8_t *)&now.tv_nsec,
526 state->inject_counter[RAND_SRC_TIMING] = 0;
527 add_buffer_randomness_state(state,
528 (const uint8_t *)&now.tv_nsec,
534 * In the second call the globaldata structure has enough
535 * differentiation to give us decent initial divergence
536 * between cpus. It isn't really all that random but its
537 * better than nothing.
539 state->inject_counter[RAND_SRC_THREAD2] = 0;
540 add_buffer_randomness_state(state,
546 * Warm up the generator to get rid of weak initial states.
548 for (i = 0; i < 10; ++i)
549 IBAA_Call(&state->ibaa);
552 * Chain to next cpu to create as much divergence as
555 state->inject_counter[RAND_SRC_TIMING] = 0;
556 add_buffer_randomness_state(state, buf, sizeof(buf),
558 read_random(buf, sizeof(buf), 1);
562 SYSINIT(rand1, SI_BOOT2_POST_SMP, SI_ORDER_SECOND, rand_initialize, 0);
568 add_keyboard_randomness(u_char scancode)
570 struct csprng_state *state;
572 state = iterate_csprng_state(1);
574 spin_lock(&state->spin);
575 L15_Vector(&state->l15,
576 (const LByteType *)&scancode, sizeof (scancode));
577 ++state->nrandevents;
579 spin_unlock(&state->spin);
580 add_interrupt_randomness(0);
585 * Interrupt events. This is SMP safe and allowed to race.
587 * This adjusts rand_thread_value which will be incorporated into the next
588 * time-buffered seed. It does not effect the seeding period per-say.
591 add_interrupt_randomness(int intr)
594 rand_thread_value = (rand_thread_value << 4) ^ 1 ^
595 ((int)rdtsc() % 151);
597 ++rand_thread_value; /* ~1 bit */
601 * Add entropy to our rng. Half the time we add the entropy to both
602 * csprngs and the other half of the time we add the entropy to one
603 * or the other (so both don't get generated from the same entropy).
606 add_buffer_randomness_state(struct csprng_state *state,
607 const char *buf, int bytes, int srcid)
612 spin_lock(&state->spin);
613 ic = ++state->inject_counter[srcid & 255];
615 L15_Vector(&state->l15, (const LByteType *)buf, bytes);
616 IBAA_Vector(&state->ibaa, buf, bytes);
617 csprng_add_entropy(state, srcid & RAND_SRC_MASK,
618 (const uint8_t *)buf, bytes, 0);
620 L15_Vector(&state->l15, (const LByteType *)buf, bytes);
621 IBAA_Vector(&state->ibaa, buf, bytes);
623 csprng_add_entropy(state, srcid & RAND_SRC_MASK,
624 (const uint8_t *)buf, bytes, 0);
626 ++state->nrandevents;
627 state->nrandseed += bytes;
628 spin_unlock(&state->spin);
638 * Add buffer randomness from miscellaneous sources. Large amounts of
639 * generic random data will be split across available cpus.
642 add_buffer_randomness(const char *buf, int bytes)
644 struct csprng_state *state;
646 state = iterate_csprng_state(bytes);
647 return add_buffer_randomness_state(state, buf, bytes, RAND_SRC_UNKNOWN);
651 add_buffer_randomness_src(const char *buf, int bytes, int srcid)
653 struct csprng_state *state;
656 while (csprng_pcpu && bytes) {
658 if (srcid & RAND_SRCF_PCPU) {
659 state = &csprng_pcpu[mycpu->gd_cpuid];
661 state = iterate_csprng_state(bytes);
665 add_buffer_randomness_state(state, buf, bytes, srcid);
673 * Kqueue filter (always succeeds)
676 random_filter_read(struct knote *kn, long hint)
682 * Heavy weight random number generator. May return less then the
683 * requested number of bytes.
685 * Instead of stopping early,
688 read_random(void *buf, u_int nbytes, int unlimited)
690 struct csprng_state *state;
693 if (csprng_pcpu == NULL) {
694 kprintf("read_random: csprng not yet ready\n");
697 state = &csprng_pcpu[mycpu->gd_cpuid];
699 spin_lock(&state->spin);
700 if (rand_mode == 0) {
701 /* Only use CSPRNG */
702 i = csprng_get_random(state, buf, nbytes, 0, unlimited);
703 } else if (rand_mode == 1) {
705 for (i = 0; i < nbytes; i++)
706 ((u_char *)buf)[i] = IBAA_Byte(&state->ibaa);
708 /* Mix both CSPRNG and IBAA */
709 i = csprng_get_random(state, buf, nbytes, 0, unlimited);
710 for (j = 0; j < i; j++)
711 ((u_char *)buf)[j] ^= IBAA_Byte(&state->ibaa);
713 spin_unlock(&state->spin);
714 add_interrupt_randomness(0);
716 return (i > 0) ? i : 0;
720 * Read random data via sysctl().
724 sysctl_kern_random(SYSCTL_HANDLER_ARGS)
735 if ((r = n) > sizeof(buf))
737 read_random(buf, r, 1);
738 error = SYSCTL_OUT(req, buf, r);
747 sys_getrandom(struct getrandom_args *uap)
756 bytes = (ssize_t)uap->len;
765 n = (ssize_t)sizeof(buf);
768 read_random(buf, n, 1);
769 error = copyout(buf, (char *)uap->buf + r, n);
774 if (++sigcnt == 128) {
776 if (CURSIG_NOBLOCK(curthread->td_lwp) != 0) {
783 uap->sysmsg_szresult = r;
789 * Change the random mode via sysctl().
793 rand_mode_to_str(int mode)
809 sysctl_kern_rand_mode(SYSCTL_HANDLER_ARGS)
814 strncpy(mode, rand_mode_to_str(rand_mode), sizeof(mode)-1);
815 error = sysctl_handle_string(oidp, mode, sizeof(mode), req);
816 if (error || req->newptr == NULL)
819 if ((strncmp(mode, "csprng", sizeof(mode))) == 0)
821 else if ((strncmp(mode, "ibaa", sizeof(mode))) == 0)
823 else if ((strncmp(mode, "mixed", sizeof(mode))) == 0)
832 * Random number generator helper thread. This limits code overhead from
833 * high frequency events by delaying the clearing of rand_thread_value.
835 * This is a time-buffered loop, with a randomizing delay. Note that interrupt
836 * entropy does not cause the thread to wakeup any faster, but does improve the
837 * quality of the entropy produced.
839 * In addition, we pull statistics from available cpus.
843 rand_thread_loop(void *dummy)
845 struct csprng_state *state;
850 struct timespec last;
853 bzero(&last, sizeof(last));
859 wcpu = (wcpu + 1) % ncpus;
860 state = &csprng_pcpu[wcpu];
861 rgd = globaldata_find(wcpu);
863 NANOUP_EVENT(&last, state);
864 spin_lock(&state->spin);
865 count = (uint8_t)L15_Byte(&state->l15);
866 spin_unlock(&state->spin);
869 * Calculate 1/10 of a second to 2/10 of a second, fine-grained
870 * using a L15_Byte() feedback.
872 * Go faster in the first 1200 seconds after boot. This effects
873 * the time-after-next interrupt (pipeline delay).
875 count = sys_cputimer->freq * (count + 256) / (256 * 10);
876 if (time_uptime < 120)
877 count = count / 10 + 1;
878 systimer_rand.periodic = count;
881 * Force cpus to diverge. Chained state and per-cpu state
884 add_buffer_randomness_state(state,
887 add_buffer_randomness_state(state,
888 (void *)&rgd->gd_cnt,
891 add_buffer_randomness_state(state,
892 (void *)&rgd->gd_vmtotal,
893 sizeof(rgd->gd_vmtotal),
896 read_random(buf, sizeof(buf), 1);
898 tsleep(rand_td, 0, "rwait", 0);
903 * Systimer trigger - fine-grained random trigger
907 rand_thread_wakeup(struct systimer *timer, int in_ipi, struct intrframe *frame)
914 rand_thread_init(void)
916 systimer_init_periodic_nq(&systimer_rand, rand_thread_wakeup, NULL, 25);
917 lwkt_create(rand_thread_loop, NULL, &rand_td, NULL, 0, 0, "random");
920 SYSINIT(rand2, SI_SUB_HELPER_THREADS, SI_ORDER_ANY, rand_thread_init, 0);
923 * Caller is time-buffered. Incorporate any accumulated interrupt randomness
924 * as well as the high frequency bits of the TSC.
926 * A delta nanoseconds value is used to remove absolute time from the generated
927 * entropy. Even though we are pushing 32 bits, this entropy is probably only
928 * good for one or two bits without any interrupt sources, and possibly
932 NANOUP_EVENT(struct timespec *last, struct csprng_state *state)
938 * Delta nanoseconds since last event
941 nsec = now.tv_nsec - last->tv_nsec;
945 * Interrupt randomness.
947 nsec ^= rand_thread_value;
950 * The TSC, if present, generally has an even higher
951 * resolution. Integrate a portion of it into our seed.
954 nsec ^= (rdtsc() & 255) << 8;
959 add_buffer_randomness_state(state,
960 (const uint8_t *)&nsec, sizeof(nsec),