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54a5ba13 MC |
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" | |
3090c980 | 12 | #include "qemu/guest-random.h" |
0b8fa32f | 13 | #include "qemu/module.h" |
54a5ba13 | 14 | #include "hw/misc/bcm2835_rng.h" |
d6454270 | 15 | #include "migration/vmstate.h" |
54a5ba13 | 16 | |
373442ea PM |
17 | static uint32_t get_random_bytes(void) |
18 | { | |
19 | uint32_t res; | |
373442ea | 20 | |
3090c980 RH |
21 | /* |
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 | qemu_guest_getrandom_nofail(&res, sizeof(res)); | |
373442ea PM |
34 | return res; |
35 | } | |
36 | ||
54a5ba13 MC |
37 | static uint64_t bcm2835_rng_read(void *opaque, hwaddr offset, |
38 | unsigned size) | |
39 | { | |
40 | BCM2835RngState *s = (BCM2835RngState *)opaque; | |
41 | uint32_t res = 0; | |
42 | ||
43 | assert(size == 4); | |
44 | ||
45 | switch (offset) { | |
46 | case 0x0: /* rng_ctrl */ | |
47 | res = s->rng_ctrl; | |
48 | break; | |
49 | case 0x4: /* rng_status */ | |
50 | res = s->rng_status | (1 << 24); | |
51 | break; | |
52 | case 0x8: /* rng_data */ | |
373442ea | 53 | res = get_random_bytes(); |
54a5ba13 MC |
54 | break; |
55 | ||
56 | default: | |
57 | qemu_log_mask(LOG_GUEST_ERROR, | |
58 | "bcm2835_rng_read: Bad offset %x\n", | |
59 | (int)offset); | |
60 | res = 0; | |
61 | break; | |
62 | } | |
63 | ||
64 | return res; | |
65 | } | |
66 | ||
67 | static void bcm2835_rng_write(void *opaque, hwaddr offset, | |
68 | uint64_t value, unsigned size) | |
69 | { | |
70 | BCM2835RngState *s = (BCM2835RngState *)opaque; | |
71 | ||
72 | assert(size == 4); | |
73 | ||
74 | switch (offset) { | |
75 | case 0x0: /* rng_ctrl */ | |
76 | s->rng_ctrl = value; | |
77 | break; | |
78 | case 0x4: /* rng_status */ | |
79 | /* we shouldn't let the guest write to bits [31..20] */ | |
80 | s->rng_status &= ~0xFFFFF; /* clear 20 lower bits */ | |
81 | s->rng_status |= value & 0xFFFFF; /* set them to new value */ | |
82 | break; | |
83 | ||
84 | default: | |
85 | qemu_log_mask(LOG_GUEST_ERROR, | |
86 | "bcm2835_rng_write: Bad offset %x\n", | |
87 | (int)offset); | |
88 | break; | |
89 | } | |
90 | } | |
91 | ||
92 | static const MemoryRegionOps bcm2835_rng_ops = { | |
93 | .read = bcm2835_rng_read, | |
94 | .write = bcm2835_rng_write, | |
95 | .endianness = DEVICE_NATIVE_ENDIAN, | |
96 | }; | |
97 | ||
98 | static const VMStateDescription vmstate_bcm2835_rng = { | |
99 | .name = TYPE_BCM2835_RNG, | |
100 | .version_id = 1, | |
101 | .minimum_version_id = 1, | |
102 | .fields = (VMStateField[]) { | |
103 | VMSTATE_UINT32(rng_ctrl, BCM2835RngState), | |
104 | VMSTATE_UINT32(rng_status, BCM2835RngState), | |
105 | VMSTATE_END_OF_LIST() | |
106 | } | |
107 | }; | |
108 | ||
109 | static void bcm2835_rng_init(Object *obj) | |
110 | { | |
111 | BCM2835RngState *s = BCM2835_RNG(obj); | |
112 | ||
113 | memory_region_init_io(&s->iomem, obj, &bcm2835_rng_ops, s, | |
114 | TYPE_BCM2835_RNG, 0x10); | |
115 | sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->iomem); | |
116 | } | |
117 | ||
118 | static void bcm2835_rng_reset(DeviceState *dev) | |
119 | { | |
120 | BCM2835RngState *s = BCM2835_RNG(dev); | |
121 | ||
122 | s->rng_ctrl = 0; | |
123 | s->rng_status = 0; | |
124 | } | |
125 | ||
126 | static void bcm2835_rng_class_init(ObjectClass *klass, void *data) | |
127 | { | |
128 | DeviceClass *dc = DEVICE_CLASS(klass); | |
129 | ||
130 | dc->reset = bcm2835_rng_reset; | |
131 | dc->vmsd = &vmstate_bcm2835_rng; | |
132 | } | |
133 | ||
134 | static TypeInfo bcm2835_rng_info = { | |
135 | .name = TYPE_BCM2835_RNG, | |
136 | .parent = TYPE_SYS_BUS_DEVICE, | |
137 | .instance_size = sizeof(BCM2835RngState), | |
138 | .class_init = bcm2835_rng_class_init, | |
139 | .instance_init = bcm2835_rng_init, | |
140 | }; | |
141 | ||
142 | static void bcm2835_rng_register_types(void) | |
143 | { | |
144 | type_register_static(&bcm2835_rng_info); | |
145 | } | |
146 | ||
147 | type_init(bcm2835_rng_register_types) |