LXR qemu/hw/misc/bcm2835

   1/*
   2 * BCM2835 Random Number Generator emulation
   3 *
   4 * Copyright (C) 2017 Marcin Chojnacki <marcinch7@gmail.com>
   5 *
   6 * This work is licensed under the terms of the GNU GPL, version 2 or later.
   7 * See the COPYING file in the top-level directory.
   8 */
   9
  10#include "qemu/osdep.h"
  11#include "qemu/log.h"
  12#include "qapi/error.h"
  13#include "crypto/random.h"
  14#include "hw/misc/bcm2835_rng.h"
  15
  16static uint32_t get_random_bytes(void)
  17{
  18    uint32_t res;
  19    Error *err = NULL;
  20
  21    if (qcrypto_random_bytes((uint8_t *)&res, sizeof(res), &err) < 0) {
  22        /* On failure we don't want to return the guest a non-random
  23         * value in case they're really using it for cryptographic
  24         * purposes, so the best we can do is die here.
  25         * This shouldn't happen unless something's broken.
  26         * In theory we could implement this device's full FIFO
  27         * and interrupt semantics and then just stop filling the
  28         * FIFO. That's a lot of work, though, so we assume any
  29         * errors are systematic problems and trust that if we didn't
  30         * fail as the guest inited then we won't fail later on
  31         * mid-run.
  32         */
  33        error_report_err(err);
  34        exit(1);
  35    }
  36    return res;
  37}
  38
  39static uint64_t bcm2835_rng_read(void *opaque, hwaddr offset,
  40                                 unsigned size)
  41{
  42    BCM2835RngState *s = (BCM2835RngState *)opaque;
  43    uint32_t res = 0;
  44
  45    assert(size == 4);
  46
  47    switch (offset) {
  48    case 0x0:    /* rng_ctrl */
  49        res = s->rng_ctrl;
  50        break;
  51    case 0x4:    /* rng_status */
  52        res = s->rng_status | (1 << 24);
  53        break;
  54    case 0x8:    /* rng_data */
  55        res = get_random_bytes();
  56        break;
  57
  58    default:
  59        qemu_log_mask(LOG_GUEST_ERROR,
  60                      "bcm2835_rng_read: Bad offset %x\n",
  61                      (int)offset);
  62        res = 0;
  63        break;
  64    }
  65
  66    return res;
  67}
  68
  69static void bcm2835_rng_write(void *opaque, hwaddr offset,
  70                              uint64_t value, unsigned size)
  71{
  72    BCM2835RngState *s = (BCM2835RngState *)opaque;
  73
  74    assert(size == 4);
  75
  76    switch (offset) {
  77    case 0x0:    /* rng_ctrl */
  78        s->rng_ctrl = value;
  79        break;
  80    case 0x4:    /* rng_status */
  81        /* we shouldn't let the guest write to bits [31..20] */
  82        s->rng_status &= ~0xFFFFF;        /* clear 20 lower bits */
  83        s->rng_status |= value & 0xFFFFF; /* set them to new value */
  84        break;
  85
  86    default:
  87        qemu_log_mask(LOG_GUEST_ERROR,
  88                      "bcm2835_rng_write: Bad offset %x\n",
  89                      (int)offset);
  90        break;
  91    }
  92}
  93
  94static const MemoryRegionOps bcm2835_rng_ops = {
  95    .read = bcm2835_rng_read,
  96    .write = bcm2835_rng_write,
  97    .endianness = DEVICE_NATIVE_ENDIAN,
  98};
  99
 100static const VMStateDescription vmstate_bcm2835_rng = {
 101    .name = TYPE_BCM2835_RNG,
 102    .version_id = 1,
 103    .minimum_version_id = 1,
 104    .fields = (VMStateField[]) {
 105        VMSTATE_UINT32(rng_ctrl, BCM2835RngState),
 106        VMSTATE_UINT32(rng_status, BCM2835RngState),
 107        VMSTATE_END_OF_LIST()
 108    }
 109};
 110
 111static void bcm2835_rng_init(Object *obj)
 112{
 113    BCM2835RngState *s = BCM2835_RNG(obj);
 114
 115    memory_region_init_io(&s->iomem, obj, &bcm2835_rng_ops, s,
 116                          TYPE_BCM2835_RNG, 0x10);
 117    sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->iomem);
 118}
 119
 120static void bcm2835_rng_reset(DeviceState *dev)
 121{
 122    BCM2835RngState *s = BCM2835_RNG(dev);
 123
 124    s->rng_ctrl = 0;
 125    s->rng_status = 0;
 126}
 127
 128static void bcm2835_rng_class_init(ObjectClass *klass, void *data)
 129{
 130    DeviceClass *dc = DEVICE_CLASS(klass);
 131
 132    dc->reset = bcm2835_rng_reset;
 133    dc->vmsd = &vmstate_bcm2835_rng;
 134}
 135
 136static TypeInfo bcm2835_rng_info = {
 137    .name          = TYPE_BCM2835_RNG,
 138    .parent        = TYPE_SYS_BUS_DEVICE,
 139    .instance_size = sizeof(BCM2835RngState),
 140    .class_init    = bcm2835_rng_class_init,
 141    .instance_init = bcm2835_rng_init,
 142};
 143
 144static void bcm2835_rng_register_types(void)
 145{
 146    type_register_static(&bcm2835_rng_info);
 147}
 148
 149type_init(bcm2835_rng_register_types)
 150