Marcin Chojnacki | 54a5ba1 | 2017-02-28 12:08:13 +0000 | [diff] [blame] | 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" |
Richard Henderson | 3090c98 | 2019-03-14 15:56:52 -0700 | [diff] [blame] | 12 | #include "qemu/guest-random.h" |
Marcin Chojnacki | 54a5ba1 | 2017-02-28 12:08:13 +0000 | [diff] [blame] | 13 | #include "hw/misc/bcm2835_rng.h" |
| 14 | |
Peter Maydell | 373442e | 2017-02-28 12:08:14 +0000 | [diff] [blame] | 15 | static uint32_t get_random_bytes(void) |
| 16 | { |
| 17 | uint32_t res; |
Peter Maydell | 373442e | 2017-02-28 12:08:14 +0000 | [diff] [blame] | 18 | |
Richard Henderson | 3090c98 | 2019-03-14 15:56:52 -0700 | [diff] [blame] | 19 | /* |
| 20 | * On failure we don't want to return the guest a non-random |
| 21 | * value in case they're really using it for cryptographic |
| 22 | * purposes, so the best we can do is die here. |
| 23 | * This shouldn't happen unless something's broken. |
| 24 | * In theory we could implement this device's full FIFO |
| 25 | * and interrupt semantics and then just stop filling the |
| 26 | * FIFO. That's a lot of work, though, so we assume any |
| 27 | * errors are systematic problems and trust that if we didn't |
| 28 | * fail as the guest inited then we won't fail later on |
| 29 | * mid-run. |
| 30 | */ |
| 31 | qemu_guest_getrandom_nofail(&res, sizeof(res)); |
Peter Maydell | 373442e | 2017-02-28 12:08:14 +0000 | [diff] [blame] | 32 | return res; |
| 33 | } |
| 34 | |
Marcin Chojnacki | 54a5ba1 | 2017-02-28 12:08:13 +0000 | [diff] [blame] | 35 | static uint64_t bcm2835_rng_read(void *opaque, hwaddr offset, |
| 36 | unsigned size) |
| 37 | { |
| 38 | BCM2835RngState *s = (BCM2835RngState *)opaque; |
| 39 | uint32_t res = 0; |
| 40 | |
| 41 | assert(size == 4); |
| 42 | |
| 43 | switch (offset) { |
| 44 | case 0x0: /* rng_ctrl */ |
| 45 | res = s->rng_ctrl; |
| 46 | break; |
| 47 | case 0x4: /* rng_status */ |
| 48 | res = s->rng_status | (1 << 24); |
| 49 | break; |
| 50 | case 0x8: /* rng_data */ |
Peter Maydell | 373442e | 2017-02-28 12:08:14 +0000 | [diff] [blame] | 51 | res = get_random_bytes(); |
Marcin Chojnacki | 54a5ba1 | 2017-02-28 12:08:13 +0000 | [diff] [blame] | 52 | break; |
| 53 | |
| 54 | default: |
| 55 | qemu_log_mask(LOG_GUEST_ERROR, |
| 56 | "bcm2835_rng_read: Bad offset %x\n", |
| 57 | (int)offset); |
| 58 | res = 0; |
| 59 | break; |
| 60 | } |
| 61 | |
| 62 | return res; |
| 63 | } |
| 64 | |
| 65 | static void bcm2835_rng_write(void *opaque, hwaddr offset, |
| 66 | uint64_t value, unsigned size) |
| 67 | { |
| 68 | BCM2835RngState *s = (BCM2835RngState *)opaque; |
| 69 | |
| 70 | assert(size == 4); |
| 71 | |
| 72 | switch (offset) { |
| 73 | case 0x0: /* rng_ctrl */ |
| 74 | s->rng_ctrl = value; |
| 75 | break; |
| 76 | case 0x4: /* rng_status */ |
| 77 | /* we shouldn't let the guest write to bits [31..20] */ |
| 78 | s->rng_status &= ~0xFFFFF; /* clear 20 lower bits */ |
| 79 | s->rng_status |= value & 0xFFFFF; /* set them to new value */ |
| 80 | break; |
| 81 | |
| 82 | default: |
| 83 | qemu_log_mask(LOG_GUEST_ERROR, |
| 84 | "bcm2835_rng_write: Bad offset %x\n", |
| 85 | (int)offset); |
| 86 | break; |
| 87 | } |
| 88 | } |
| 89 | |
| 90 | static const MemoryRegionOps bcm2835_rng_ops = { |
| 91 | .read = bcm2835_rng_read, |
| 92 | .write = bcm2835_rng_write, |
| 93 | .endianness = DEVICE_NATIVE_ENDIAN, |
| 94 | }; |
| 95 | |
| 96 | static const VMStateDescription vmstate_bcm2835_rng = { |
| 97 | .name = TYPE_BCM2835_RNG, |
| 98 | .version_id = 1, |
| 99 | .minimum_version_id = 1, |
| 100 | .fields = (VMStateField[]) { |
| 101 | VMSTATE_UINT32(rng_ctrl, BCM2835RngState), |
| 102 | VMSTATE_UINT32(rng_status, BCM2835RngState), |
| 103 | VMSTATE_END_OF_LIST() |
| 104 | } |
| 105 | }; |
| 106 | |
| 107 | static void bcm2835_rng_init(Object *obj) |
| 108 | { |
| 109 | BCM2835RngState *s = BCM2835_RNG(obj); |
| 110 | |
| 111 | memory_region_init_io(&s->iomem, obj, &bcm2835_rng_ops, s, |
| 112 | TYPE_BCM2835_RNG, 0x10); |
| 113 | sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->iomem); |
| 114 | } |
| 115 | |
| 116 | static void bcm2835_rng_reset(DeviceState *dev) |
| 117 | { |
| 118 | BCM2835RngState *s = BCM2835_RNG(dev); |
| 119 | |
| 120 | s->rng_ctrl = 0; |
| 121 | s->rng_status = 0; |
| 122 | } |
| 123 | |
| 124 | static void bcm2835_rng_class_init(ObjectClass *klass, void *data) |
| 125 | { |
| 126 | DeviceClass *dc = DEVICE_CLASS(klass); |
| 127 | |
| 128 | dc->reset = bcm2835_rng_reset; |
| 129 | dc->vmsd = &vmstate_bcm2835_rng; |
| 130 | } |
| 131 | |
| 132 | static TypeInfo bcm2835_rng_info = { |
| 133 | .name = TYPE_BCM2835_RNG, |
| 134 | .parent = TYPE_SYS_BUS_DEVICE, |
| 135 | .instance_size = sizeof(BCM2835RngState), |
| 136 | .class_init = bcm2835_rng_class_init, |
| 137 | .instance_init = bcm2835_rng_init, |
| 138 | }; |
| 139 | |
| 140 | static void bcm2835_rng_register_types(void) |
| 141 | { |
| 142 | type_register_static(&bcm2835_rng_info); |
| 143 | } |
| 144 | |
| 145 | type_init(bcm2835_rng_register_types) |