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54a5ba13 MC |
1 | /* |
2 | * BCM2835 Random Number Generator emulation | |
3 | * | |
4 | * Copyright (C) 2017 Marcin Chojnacki <[email protected]> | |
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" | |
373442ea PM |
12 | #include "qapi/error.h" |
13 | #include "crypto/random.h" | |
54a5ba13 MC |
14 | #include "hw/misc/bcm2835_rng.h" |
15 | ||
373442ea PM |
16 | static 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 | ||
54a5ba13 MC |
39 | static 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 */ | |
373442ea | 55 | res = get_random_bytes(); |
54a5ba13 MC |
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 | ||
69 | static 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 | ||
94 | static const MemoryRegionOps bcm2835_rng_ops = { | |
95 | .read = bcm2835_rng_read, | |
96 | .write = bcm2835_rng_write, | |
97 | .endianness = DEVICE_NATIVE_ENDIAN, | |
98 | }; | |
99 | ||
100 | static 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 | ||
111 | static 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 | ||
120 | static 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 | ||
128 | static 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 | ||
136 | static 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 | ||
144 | static void bcm2835_rng_register_types(void) | |
145 | { | |
146 | type_register_static(&bcm2835_rng_info); | |
147 | } | |
148 | ||
149 | type_init(bcm2835_rng_register_types) |