2 * Copyright (c) 2012 Alex Hornung <alex@alexhornung.com>.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in
13 * the documentation and/or other materials provided with the
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
19 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
20 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
22 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
24 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
25 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
26 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 #include <sys/param.h>
30 #include <sys/systm.h>
31 #include <sys/kernel.h>
33 #include <sys/libkern.h>
34 #include <sys/module.h>
36 #include <sys/random.h>
37 #include <sys/malloc.h>
38 #include <sys/sysctl.h>
40 #include <machine/specialreg.h>
45 * The RDRAND instruction is a very slow instruction, burning approximately
46 * 0.79uS per 64-bit word on a modern ryzen cpu. Intel cpu's run this
47 * instruction far more quickly. The quality of the results are unknown
48 * either way. The add_buffer_randomness() call is also not cheap.
50 * Our code harvests at a 10hz rate on every single core, and also chains
51 * some entropy from core to core so honestly it doesn't take much to really
52 * mix things up. Use a decent size (16 or 32 bytes should be good).
54 #define RDRAND_ALIGN(p) (void *)(roundup2((uintptr_t)(p), 16))
55 #define RDRAND_SIZE 16
57 static int rdrand_debug;
58 SYSCTL_INT(_debug, OID_AUTO, rdrand, CTLFLAG_RW, &rdrand_debug, 0,
59 "Enable rdrand debugging");
62 struct callout *sc_rng_co;
67 static void rdrand_rng_harvest(void *);
68 int rdrand_rng(uint8_t *out, long limit);
72 rdrand_identify(driver_t *drv, device_t parent)
75 /* NB: order 10 is so we get attached after h/w devices */
76 if (device_find_child(parent, "rdrand", -1) == NULL &&
77 BUS_ADD_CHILD(parent, parent, 10, "rdrand", -1) == 0)
78 panic("rdrand: could not attach");
83 rdrand_probe(device_t dev)
86 if ((cpu_feature2 & CPUID2_RDRAND) == 0) {
87 device_printf(dev, "No RdRand support.\n");
91 device_set_desc(dev, "RdRand RNG");
97 rdrand_attach(device_t dev)
99 struct rdrand_softc *sc;
102 sc = device_get_softc(dev);
105 sc->sc_rng_ticks = hz / 10;
107 sc->sc_rng_ticks = 1;
109 sc->sc_rng_co = kmalloc(ncpus * sizeof(*sc->sc_rng_co),
110 M_TEMP, M_WAITOK | M_ZERO);
112 for (i = 0; i < ncpus; ++i) {
113 callout_init_mp(&sc->sc_rng_co[i]);
114 callout_reset_bycpu(&sc->sc_rng_co[i], sc->sc_rng_ticks,
115 rdrand_rng_harvest, sc, i);
123 rdrand_detach(device_t dev)
125 struct rdrand_softc *sc;
128 sc = device_get_softc(dev);
130 for (i = 0; i < ncpus; ++i) {
131 callout_terminate(&sc->sc_rng_co[i]);
139 rdrand_rng_harvest(void *arg)
141 struct rdrand_softc *sc = arg;
142 uint8_t randomness[RDRAND_SIZE + 32];
143 uint8_t *arandomness; /* randomness aligned */
146 arandomness = RDRAND_ALIGN(randomness);
148 cnt = rdrand_rng(arandomness, RDRAND_SIZE);
149 if (cnt > 0 && cnt < sizeof(randomness)) {
150 add_buffer_randomness_src(arandomness, cnt,
154 if (rdrand_debug > 0) {
156 kprintf("rdrand(%d,cpu=%d): %02x %02x %02x %02x...\n",
157 cnt, mycpu->gd_cpuid,
165 callout_reset(&sc->sc_rng_co[mycpu->gd_cpuid], sc->sc_rng_ticks,
166 rdrand_rng_harvest, sc);
170 static device_method_t rdrand_methods[] = {
171 DEVMETHOD(device_identify, rdrand_identify),
172 DEVMETHOD(device_probe, rdrand_probe),
173 DEVMETHOD(device_attach, rdrand_attach),
174 DEVMETHOD(device_detach, rdrand_detach),
180 static driver_t rdrand_driver = {
183 sizeof(struct rdrand_softc),
186 static devclass_t rdrand_devclass;
188 DRIVER_MODULE(rdrand, nexus, rdrand_driver, rdrand_devclass, NULL, NULL);
189 MODULE_VERSION(rdrand, 1);
190 MODULE_DEPEND(rdrand, crypto, 1, 1, 1);