Commit | Line | Data |
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fd534e9b | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
f7f510ec RR |
2 | /* |
3 | * Randomness driver for virtio | |
4 | * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation | |
f7f510ec | 5 | */ |
bb347d98 | 6 | |
f7f510ec RR |
7 | #include <linux/err.h> |
8 | #include <linux/hw_random.h> | |
9 | #include <linux/scatterlist.h> | |
10 | #include <linux/spinlock.h> | |
11 | #include <linux/virtio.h> | |
12 | #include <linux/virtio_rng.h> | |
c22405c9 | 13 | #include <linux/module.h> |
b69df6cd | 14 | #include <linux/slab.h> |
f7f510ec | 15 | |
a17597d3 | 16 | static DEFINE_IDA(rng_index_ida); |
08e53fbd AK |
17 | |
18 | struct virtrng_info { | |
08e53fbd AK |
19 | struct hwrng hwrng; |
20 | struct virtqueue *vq; | |
a17597d3 SL |
21 | char name[25]; |
22 | int index; | |
5c062734 | 23 | bool hwrng_register_done; |
f4981956 | 24 | bool hwrng_removed; |
bf3175bc LV |
25 | /* data transfer */ |
26 | struct completion have_data; | |
27 | unsigned int data_avail; | |
5c8e9330 | 28 | unsigned int data_idx; |
bf3175bc LV |
29 | /* minimal size returned by rng_buffer_size() */ |
30 | #if SMP_CACHE_BYTES < 32 | |
31 | u8 data[32]; | |
32 | #else | |
33 | u8 data[SMP_CACHE_BYTES]; | |
34 | #endif | |
08e53fbd | 35 | }; |
f7f510ec RR |
36 | |
37 | static void random_recv_done(struct virtqueue *vq) | |
38 | { | |
08e53fbd AK |
39 | struct virtrng_info *vi = vq->vdev->priv; |
40 | ||
e5b89542 | 41 | /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */ |
08e53fbd | 42 | if (!virtqueue_get_buf(vi->vq, &vi->data_avail)) |
e5b89542 | 43 | return; |
f7f510ec | 44 | |
5c8e9330 | 45 | vi->data_idx = 0; |
5c8e9330 | 46 | |
08e53fbd | 47 | complete(&vi->have_data); |
f7f510ec RR |
48 | } |
49 | ||
9a4b612d | 50 | static void request_entropy(struct virtrng_info *vi) |
f7f510ec RR |
51 | { |
52 | struct scatterlist sg; | |
53 | ||
9a4b612d LV |
54 | reinit_completion(&vi->have_data); |
55 | vi->data_avail = 0; | |
56 | vi->data_idx = 0; | |
57 | ||
bf3175bc | 58 | sg_init_one(&sg, vi->data, sizeof(vi->data)); |
bb347d98 | 59 | |
f7f510ec | 60 | /* There should always be room for one buffer. */ |
bf3175bc | 61 | virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL); |
bb347d98 | 62 | |
08e53fbd | 63 | virtqueue_kick(vi->vq); |
f7f510ec RR |
64 | } |
65 | ||
5c8e9330 LV |
66 | static unsigned int copy_data(struct virtrng_info *vi, void *buf, |
67 | unsigned int size) | |
68 | { | |
69 | size = min_t(unsigned int, size, vi->data_avail); | |
70 | memcpy(buf, vi->data + vi->data_idx, size); | |
71 | vi->data_idx += size; | |
72 | vi->data_avail -= size; | |
9a4b612d LV |
73 | if (vi->data_avail == 0) |
74 | request_entropy(vi); | |
5c8e9330 LV |
75 | return size; |
76 | } | |
77 | ||
bb347d98 | 78 | static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) |
f7f510ec | 79 | { |
cc8744e1 | 80 | int ret; |
08e53fbd | 81 | struct virtrng_info *vi = (struct virtrng_info *)rng->priv; |
bf3175bc LV |
82 | unsigned int chunk; |
83 | size_t read; | |
f7f510ec | 84 | |
f4981956 AK |
85 | if (vi->hwrng_removed) |
86 | return -ENODEV; | |
87 | ||
5c8e9330 LV |
88 | read = 0; |
89 | ||
90 | /* copy available data */ | |
91 | if (vi->data_avail) { | |
92 | chunk = copy_data(vi, buf, size); | |
93 | size -= chunk; | |
94 | read += chunk; | |
bb347d98 IM |
95 | } |
96 | ||
f7f510ec | 97 | if (!wait) |
5c8e9330 | 98 | return read; |
f7f510ec | 99 | |
5c8e9330 LV |
100 | /* We have already copied available entropy, |
101 | * so either size is 0 or data_avail is 0 | |
102 | */ | |
bf3175bc | 103 | while (size != 0) { |
9a4b612d | 104 | /* data_avail is 0 but a request is pending */ |
bf3175bc LV |
105 | ret = wait_for_completion_killable(&vi->have_data); |
106 | if (ret < 0) | |
107 | return ret; | |
2bb31abd LV |
108 | /* if vi->data_avail is 0, we have been interrupted |
109 | * by a cleanup, but buffer stays in the queue | |
110 | */ | |
111 | if (vi->data_avail == 0) | |
112 | return read; | |
bf3175bc | 113 | |
5c8e9330 | 114 | chunk = copy_data(vi, buf + read, size); |
bf3175bc | 115 | size -= chunk; |
5c8e9330 | 116 | read += chunk; |
bf3175bc | 117 | } |
594de1dd | 118 | |
bf3175bc | 119 | return read; |
f7f510ec RR |
120 | } |
121 | ||
bb347d98 | 122 | static void virtio_cleanup(struct hwrng *rng) |
f7f510ec | 123 | { |
08e53fbd | 124 | struct virtrng_info *vi = (struct virtrng_info *)rng->priv; |
bb347d98 | 125 | |
9a4b612d | 126 | complete(&vi->have_data); |
08e53fbd | 127 | } |
f7f510ec | 128 | |
178d855e | 129 | static int probe_common(struct virtio_device *vdev) |
f7f510ec | 130 | { |
a17597d3 | 131 | int err, index; |
08e53fbd AK |
132 | struct virtrng_info *vi = NULL; |
133 | ||
e5d23a8c | 134 | vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL); |
a17597d3 SL |
135 | if (!vi) |
136 | return -ENOMEM; | |
137 | ||
138 | vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL); | |
139 | if (index < 0) { | |
1bbc2606 MT |
140 | err = index; |
141 | goto err_ida; | |
a17597d3 SL |
142 | } |
143 | sprintf(vi->name, "virtio_rng.%d", index); | |
08e53fbd AK |
144 | init_completion(&vi->have_data); |
145 | ||
a17597d3 SL |
146 | vi->hwrng = (struct hwrng) { |
147 | .read = virtio_read, | |
148 | .cleanup = virtio_cleanup, | |
149 | .priv = (unsigned long)vi, | |
150 | .name = vi->name, | |
34679ec7 | 151 | .quality = 1000, |
a17597d3 | 152 | }; |
08e53fbd | 153 | vdev->priv = vi; |
f7f510ec RR |
154 | |
155 | /* We expect a single virtqueue. */ | |
08e53fbd AK |
156 | vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input"); |
157 | if (IS_ERR(vi->vq)) { | |
158 | err = PTR_ERR(vi->vq); | |
1bbc2606 | 159 | goto err_find; |
e84e7a56 | 160 | } |
f7f510ec | 161 | |
22843255 JW |
162 | virtio_device_ready(vdev); |
163 | ||
9a4b612d LV |
164 | /* we always have a pending entropy request */ |
165 | request_entropy(vi); | |
166 | ||
f7f510ec | 167 | return 0; |
1bbc2606 MT |
168 | |
169 | err_find: | |
170 | ida_simple_remove(&rng_index_ida, index); | |
171 | err_ida: | |
172 | kfree(vi); | |
173 | return err; | |
f7f510ec RR |
174 | } |
175 | ||
178d855e | 176 | static void remove_common(struct virtio_device *vdev) |
f7f510ec | 177 | { |
08e53fbd | 178 | struct virtrng_info *vi = vdev->priv; |
5c062734 | 179 | |
f4981956 | 180 | vi->hwrng_removed = true; |
3856e548 | 181 | vi->data_avail = 0; |
5c8e9330 | 182 | vi->data_idx = 0; |
3856e548 | 183 | complete(&vi->have_data); |
5c062734 AS |
184 | if (vi->hwrng_register_done) |
185 | hwrng_unregister(&vi->hwrng); | |
20762071 | 186 | virtio_reset_device(vdev); |
d2a7ddda | 187 | vdev->config->del_vqs(vdev); |
a17597d3 | 188 | ida_simple_remove(&rng_index_ida, vi->index); |
08e53fbd | 189 | kfree(vi); |
f7f510ec RR |
190 | } |
191 | ||
178d855e AS |
192 | static int virtrng_probe(struct virtio_device *vdev) |
193 | { | |
194 | return probe_common(vdev); | |
195 | } | |
196 | ||
39af33fc | 197 | static void virtrng_remove(struct virtio_device *vdev) |
178d855e AS |
198 | { |
199 | remove_common(vdev); | |
200 | } | |
201 | ||
5c062734 AS |
202 | static void virtrng_scan(struct virtio_device *vdev) |
203 | { | |
204 | struct virtrng_info *vi = vdev->priv; | |
205 | int err; | |
206 | ||
207 | err = hwrng_register(&vi->hwrng); | |
208 | if (!err) | |
209 | vi->hwrng_register_done = true; | |
210 | } | |
211 | ||
89107000 | 212 | #ifdef CONFIG_PM_SLEEP |
0bc1a2ef AS |
213 | static int virtrng_freeze(struct virtio_device *vdev) |
214 | { | |
215 | remove_common(vdev); | |
216 | return 0; | |
217 | } | |
218 | ||
219 | static int virtrng_restore(struct virtio_device *vdev) | |
220 | { | |
e5cc6e79 JQ |
221 | int err; |
222 | ||
223 | err = probe_common(vdev); | |
224 | if (!err) { | |
225 | struct virtrng_info *vi = vdev->priv; | |
226 | ||
227 | /* | |
228 | * Set hwrng_removed to ensure that virtio_read() | |
229 | * does not block waiting for data before the | |
230 | * registration is complete. | |
231 | */ | |
232 | vi->hwrng_removed = true; | |
233 | err = hwrng_register(&vi->hwrng); | |
234 | if (!err) { | |
235 | vi->hwrng_register_done = true; | |
236 | vi->hwrng_removed = false; | |
237 | } | |
238 | } | |
239 | ||
240 | return err; | |
0bc1a2ef AS |
241 | } |
242 | #endif | |
243 | ||
a024d70a | 244 | static const struct virtio_device_id id_table[] = { |
f7f510ec RR |
245 | { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, |
246 | { 0 }, | |
247 | }; | |
248 | ||
d817cd52 | 249 | static struct virtio_driver virtio_rng_driver = { |
f7f510ec RR |
250 | .driver.name = KBUILD_MODNAME, |
251 | .driver.owner = THIS_MODULE, | |
252 | .id_table = id_table, | |
253 | .probe = virtrng_probe, | |
bcd2982a | 254 | .remove = virtrng_remove, |
5c062734 | 255 | .scan = virtrng_scan, |
89107000 | 256 | #ifdef CONFIG_PM_SLEEP |
0bc1a2ef AS |
257 | .freeze = virtrng_freeze, |
258 | .restore = virtrng_restore, | |
259 | #endif | |
f7f510ec RR |
260 | }; |
261 | ||
b2a17029 | 262 | module_virtio_driver(virtio_rng_driver); |
f7f510ec RR |
263 | MODULE_DEVICE_TABLE(virtio, id_table); |
264 | MODULE_DESCRIPTION("Virtio random number driver"); | |
265 | MODULE_LICENSE("GPL"); |