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/sysctl.h>
  38
  39 #include <machine/specialreg.h>
  40
  41 #define RDRAND_ALIGN(p) (void *)(roundup2((uintptr_t)(p), 16))
  42 #define RDRAND_SIZE     512
  43
  44 static int rdrand_debug;
  45 SYSCTL_INT(_debug, OID_AUTO, rdrand, CTLFLAG_RW, &rdrand_debug, 0,
  46            "Enable rdrand debugging");
  47
  48 struct rdrand_softc {
  49         struct callout  sc_rng_co;
  50         int32_t         sc_rng_ticks;
  51 };
  52
  53
  54 static void rdrand_rng_harvest(void *);
  55 int rdrand_rng(uint8_t *out, long limit);
  56
  57
  58 static void
  59 rdrand_identify(driver_t *drv, device_t parent)
  60 {
  61
  62         /* NB: order 10 is so we get attached after h/w devices */
  63         if (device_find_child(parent, "rdrand", -1) == NULL &&
  64             BUS_ADD_CHILD(parent, parent, 10, "rdrand", -1) == 0)
  65                 panic("rdrand: could not attach");
  66 }
  67
  68
  69 static int
  70 rdrand_probe(device_t dev)
  71 {
  72
  73         if ((cpu_feature2 & CPUID2_RDRAND) == 0) {
  74                 device_printf(dev, "No RdRand support.\n");
  75                 return (EINVAL);
  76         }
  77
  78         device_set_desc(dev, "RdRand RNG");
  79         return 0;
  80 }
  81
  82
  83 static int
  84 rdrand_attach(device_t dev)
  85 {
  86         struct rdrand_softc *sc;
  87
  88         sc = device_get_softc(dev);
  89
  90         if (hz > 10)
  91                 sc->sc_rng_ticks = hz / 10;
  92         else
  93                 sc->sc_rng_ticks = 1;
  94
  95         callout_init_mp(&sc->sc_rng_co);
  96         callout_reset(&sc->sc_rng_co, sc->sc_rng_ticks,
  97                       rdrand_rng_harvest, sc);
  98
  99         return 0;
 100 }
 101
 102
 103 static int
 104 rdrand_detach(device_t dev)
 105 {
 106         struct rdrand_softc *sc;
 107
 108         sc = device_get_softc(dev);
 109
 110         callout_terminate(&sc->sc_rng_co);
 111
 112         return (0);
 113 }
 114
 115
 116 static void
 117 rdrand_rng_harvest(void *arg)
 118 {
 119         struct rdrand_softc *sc = arg;
 120         uint8_t randomness[RDRAND_SIZE + 32];
 121         uint8_t *arandomness; /* randomness aligned */
 122         int cnt;
 123
 124         arandomness = RDRAND_ALIGN(randomness);
 125
 126         cnt = rdrand_rng(arandomness, RDRAND_SIZE);
 127         if (cnt > 0 && cnt < sizeof(randomness)) {
 128                 add_buffer_randomness_src(arandomness, cnt, RAND_SRC_RDRAND);
 129
 130                 if (rdrand_debug) {
 131                         kprintf("rdrand(%d): %02x %02x %02x %02x...\n",
 132                                 cnt,
 133                                 arandomness[0],
 134                                 arandomness[1],
 135                                 arandomness[2],
 136                                 arandomness[3]);
 137                 }
 138         }
 139
 140         callout_reset(&sc->sc_rng_co, sc->sc_rng_ticks,
 141                       rdrand_rng_harvest, sc);
 142 }
 143
 144
 145 static device_method_t rdrand_methods[] = {
 146         DEVMETHOD(device_identify, rdrand_identify),
 147         DEVMETHOD(device_probe, rdrand_probe),
 148         DEVMETHOD(device_attach, rdrand_attach),
 149         DEVMETHOD(device_detach, rdrand_detach),
 150
 151         DEVMETHOD_END
 152 };
 153
 154
 155 static driver_t rdrand_driver = {
 156         "rdrand",
 157         rdrand_methods,
 158         sizeof(struct rdrand_softc),
 159 };
 160
 161 static devclass_t rdrand_devclass;
 162
 163 DRIVER_MODULE(rdrand, nexus, rdrand_driver, rdrand_devclass, NULL, NULL);
 164 MODULE_VERSION(rdrand, 1);
 165 MODULE_DEPEND(rdrand, crypto, 1, 1, 1);