sys/dev/crypto/rdrand/rdrand.c

   1 /*
   2  * Copyright (c) 2012 Alex Hornung <alex@alexhornung.com>.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   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
  14  *    distribution.
  15  *
  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
  27  * SUCH DAMAGE.
  28  */
  29 #include <sys/param.h>
  30 #include <sys/systm.h>
  31 #include <sys/kernel.h>
  32 #include <sys/kobj.h>
  33 #include <sys/libkern.h>
  34 #include <sys/module.h>
  35 #include <sys/bus.h>
  36 #include <sys/random.h>
  37 #include <sys/malloc.h>
  38 #include <sys/sysctl.h>
  39
  40 #include <machine/specialreg.h>
  41
  42 #define RDRAND_ALIGN(p) (void *)(roundup2((uintptr_t)(p), 16))
  43 #define RDRAND_SIZE     512
  44
  45 static int rdrand_debug;
  46 SYSCTL_INT(_debug, OID_AUTO, rdrand, CTLFLAG_RW, &rdrand_debug, 0,
  47            "Enable rdrand debugging");
  48
  49 struct rdrand_softc {
  50         struct callout  *sc_rng_co;
  51         int32_t         sc_rng_ticks;
  52 };
  53
  54
  55 static void rdrand_rng_harvest(void *);
  56 int rdrand_rng(uint8_t *out, long limit);
  57
  58
  59 static void
  60 rdrand_identify(driver_t *drv, device_t parent)
  61 {
  62
  63         /* NB: order 10 is so we get attached after h/w devices */
  64         if (device_find_child(parent, "rdrand", -1) == NULL &&
  65             BUS_ADD_CHILD(parent, parent, 10, "rdrand", -1) == 0)
  66                 panic("rdrand: could not attach");
  67 }
  68
  69
  70 static int
  71 rdrand_probe(device_t dev)
  72 {
  73
  74         if ((cpu_feature2 & CPUID2_RDRAND) == 0) {
  75                 device_printf(dev, "No RdRand support.\n");
  76                 return (EINVAL);
  77         }
  78
  79         device_set_desc(dev, "RdRand RNG");
  80         return 0;
  81 }
  82
  83
  84 static int
  85 rdrand_attach(device_t dev)
  86 {
  87         struct rdrand_softc *sc;
  88         int i;
  89
  90         sc = device_get_softc(dev);
  91
  92         if (hz > 10)
  93                 sc->sc_rng_ticks = hz / 10;
  94         else
  95                 sc->sc_rng_ticks = 1;
  96
  97         sc->sc_rng_co = kmalloc(ncpus * sizeof(*sc->sc_rng_co),
  98                                 M_TEMP, M_WAITOK | M_ZERO);
  99
 100         for (i = 0; i < ncpus; ++i) {
 101                 callout_init_mp(&sc->sc_rng_co[i]);
 102                 callout_reset_bycpu(&sc->sc_rng_co[i], sc->sc_rng_ticks,
 103                                     rdrand_rng_harvest, sc, i);
 104         }
 105
 106         return 0;
 107 }
 108
 109
 110 static int
 111 rdrand_detach(device_t dev)
 112 {
 113         struct rdrand_softc *sc;
 114         int i;
 115
 116         sc = device_get_softc(dev);
 117
 118         for (i = 0; i < ncpus; ++i) {
 119                 callout_terminate(&sc->sc_rng_co[i]);
 120         }
 121
 122         return (0);
 123 }
 124
 125
 126 static void
 127 rdrand_rng_harvest(void *arg)
 128 {
 129         struct rdrand_softc *sc = arg;
 130         uint8_t randomness[RDRAND_SIZE + 32];
 131         uint8_t *arandomness; /* randomness aligned */
 132         int cnt;
 133
 134         arandomness = RDRAND_ALIGN(randomness);
 135
 136         cnt = rdrand_rng(arandomness, RDRAND_SIZE);
 137         if (cnt > 0 && cnt < sizeof(randomness)) {
 138                 add_buffer_randomness_src(arandomness, cnt,
 139                                           RAND_SRC_RDRAND |
 140                                           RAND_SRCF_PCPU);
 141
 142                 if (rdrand_debug > 0) {
 143                         --rdrand_debug;
 144                         kprintf("rdrand(%d,cpu=%d): %02x %02x %02x %02x...\n",
 145                                 cnt, mycpu->gd_cpuid,
 146                                 arandomness[0],
 147                                 arandomness[1],
 148                                 arandomness[2],
 149                                 arandomness[3]);
 150                 }
 151         }
 152
 153         callout_reset(&sc->sc_rng_co[mycpu->gd_cpuid], sc->sc_rng_ticks,
 154                       rdrand_rng_harvest, sc);
 155 }
 156
 157
 158 static device_method_t rdrand_methods[] = {
 159         DEVMETHOD(device_identify, rdrand_identify),
 160         DEVMETHOD(device_probe, rdrand_probe),
 161         DEVMETHOD(device_attach, rdrand_attach),
 162         DEVMETHOD(device_detach, rdrand_detach),
 163
 164         DEVMETHOD_END
 165 };
 166
 167
 168 static driver_t rdrand_driver = {
 169         "rdrand",
 170         rdrand_methods,
 171         sizeof(struct rdrand_softc),
 172 };
 173
 174 static devclass_t rdrand_devclass;
 175
 176 DRIVER_MODULE(rdrand, nexus, rdrand_driver, rdrand_devclass, NULL, NULL);
 177 MODULE_VERSION(rdrand, 1);
 178 MODULE_DEPEND(rdrand, crypto, 1, 1, 1);