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 | |
ac52578d | 7 | #include <asm/barrier.h> |
f7f510ec RR |
8 | #include <linux/err.h> |
9 | #include <linux/hw_random.h> | |
10 | #include <linux/scatterlist.h> | |
11 | #include <linux/spinlock.h> | |
12 | #include <linux/virtio.h> | |
13 | #include <linux/virtio_rng.h> | |
c22405c9 | 14 | #include <linux/module.h> |
b69df6cd | 15 | #include <linux/slab.h> |
f7f510ec | 16 | |
a17597d3 | 17 | static DEFINE_IDA(rng_index_ida); |
08e53fbd AK |
18 | |
19 | struct virtrng_info { | |
08e53fbd AK |
20 | struct hwrng hwrng; |
21 | struct virtqueue *vq; | |
a17597d3 SL |
22 | char name[25]; |
23 | int index; | |
5c062734 | 24 | bool hwrng_register_done; |
f4981956 | 25 | bool hwrng_removed; |
bf3175bc LV |
26 | /* data transfer */ |
27 | struct completion have_data; | |
28 | unsigned int data_avail; | |
5c8e9330 | 29 | unsigned int data_idx; |
bf3175bc LV |
30 | /* minimal size returned by rng_buffer_size() */ |
31 | #if SMP_CACHE_BYTES < 32 | |
32 | u8 data[32]; | |
33 | #else | |
34 | u8 data[SMP_CACHE_BYTES]; | |
35 | #endif | |
08e53fbd | 36 | }; |
f7f510ec RR |
37 | |
38 | static void random_recv_done(struct virtqueue *vq) | |
39 | { | |
08e53fbd | 40 | struct virtrng_info *vi = vq->vdev->priv; |
ac52578d | 41 | unsigned int len; |
08e53fbd | 42 | |
e5b89542 | 43 | /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */ |
ac52578d | 44 | if (!virtqueue_get_buf(vi->vq, &len)) |
e5b89542 | 45 | return; |
f7f510ec | 46 | |
ac52578d | 47 | smp_store_release(&vi->data_avail, len); |
08e53fbd | 48 | complete(&vi->have_data); |
f7f510ec RR |
49 | } |
50 | ||
9a4b612d | 51 | static void request_entropy(struct virtrng_info *vi) |
f7f510ec RR |
52 | { |
53 | struct scatterlist sg; | |
54 | ||
9a4b612d | 55 | reinit_completion(&vi->have_data); |
9a4b612d LV |
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 */ | |
ac52578d | 91 | if (smp_load_acquire(&vi->data_avail)) { |
5c8e9330 LV |
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 | ||
e4db80d8 | 138 | vi->index = index = ida_alloc(&rng_index_ida, GFP_KERNEL); |
a17597d3 | 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, | |
151 | }; | |
08e53fbd | 152 | vdev->priv = vi; |
f7f510ec RR |
153 | |
154 | /* We expect a single virtqueue. */ | |
08e53fbd AK |
155 | vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input"); |
156 | if (IS_ERR(vi->vq)) { | |
157 | err = PTR_ERR(vi->vq); | |
1bbc2606 | 158 | goto err_find; |
e84e7a56 | 159 | } |
f7f510ec | 160 | |
22843255 JW |
161 | virtio_device_ready(vdev); |
162 | ||
9a4b612d LV |
163 | /* we always have a pending entropy request */ |
164 | request_entropy(vi); | |
165 | ||
f7f510ec | 166 | return 0; |
1bbc2606 MT |
167 | |
168 | err_find: | |
e4db80d8 | 169 | ida_free(&rng_index_ida, index); |
1bbc2606 MT |
170 | err_ida: |
171 | kfree(vi); | |
172 | return err; | |
f7f510ec RR |
173 | } |
174 | ||
178d855e | 175 | static void remove_common(struct virtio_device *vdev) |
f7f510ec | 176 | { |
08e53fbd | 177 | struct virtrng_info *vi = vdev->priv; |
5c062734 | 178 | |
f4981956 | 179 | vi->hwrng_removed = true; |
3856e548 | 180 | vi->data_avail = 0; |
5c8e9330 | 181 | vi->data_idx = 0; |
3856e548 | 182 | complete(&vi->have_data); |
5c062734 AS |
183 | if (vi->hwrng_register_done) |
184 | hwrng_unregister(&vi->hwrng); | |
20762071 | 185 | virtio_reset_device(vdev); |
d2a7ddda | 186 | vdev->config->del_vqs(vdev); |
e4db80d8 | 187 | ida_free(&rng_index_ida, vi->index); |
08e53fbd | 188 | kfree(vi); |
f7f510ec RR |
189 | } |
190 | ||
178d855e AS |
191 | static int virtrng_probe(struct virtio_device *vdev) |
192 | { | |
193 | return probe_common(vdev); | |
194 | } | |
195 | ||
39af33fc | 196 | static void virtrng_remove(struct virtio_device *vdev) |
178d855e AS |
197 | { |
198 | remove_common(vdev); | |
199 | } | |
200 | ||
5c062734 AS |
201 | static void virtrng_scan(struct virtio_device *vdev) |
202 | { | |
203 | struct virtrng_info *vi = vdev->priv; | |
204 | int err; | |
205 | ||
206 | err = hwrng_register(&vi->hwrng); | |
207 | if (!err) | |
208 | vi->hwrng_register_done = true; | |
209 | } | |
210 | ||
0bc1a2ef AS |
211 | static int virtrng_freeze(struct virtio_device *vdev) |
212 | { | |
213 | remove_common(vdev); | |
214 | return 0; | |
215 | } | |
216 | ||
217 | static int virtrng_restore(struct virtio_device *vdev) | |
218 | { | |
e5cc6e79 JQ |
219 | int err; |
220 | ||
221 | err = probe_common(vdev); | |
222 | if (!err) { | |
223 | struct virtrng_info *vi = vdev->priv; | |
224 | ||
225 | /* | |
226 | * Set hwrng_removed to ensure that virtio_read() | |
227 | * does not block waiting for data before the | |
228 | * registration is complete. | |
229 | */ | |
230 | vi->hwrng_removed = true; | |
231 | err = hwrng_register(&vi->hwrng); | |
232 | if (!err) { | |
233 | vi->hwrng_register_done = true; | |
234 | vi->hwrng_removed = false; | |
235 | } | |
236 | } | |
237 | ||
238 | return err; | |
0bc1a2ef | 239 | } |
0bc1a2ef | 240 | |
a024d70a | 241 | static const struct virtio_device_id id_table[] = { |
f7f510ec RR |
242 | { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, |
243 | { 0 }, | |
244 | }; | |
245 | ||
d817cd52 | 246 | static struct virtio_driver virtio_rng_driver = { |
f7f510ec | 247 | .driver.name = KBUILD_MODNAME, |
f7f510ec RR |
248 | .id_table = id_table, |
249 | .probe = virtrng_probe, | |
bcd2982a | 250 | .remove = virtrng_remove, |
5c062734 | 251 | .scan = virtrng_scan, |
7c18e3c6 MK |
252 | .freeze = pm_sleep_ptr(virtrng_freeze), |
253 | .restore = pm_sleep_ptr(virtrng_restore), | |
f7f510ec RR |
254 | }; |
255 | ||
b2a17029 | 256 | module_virtio_driver(virtio_rng_driver); |
f7f510ec RR |
257 | MODULE_DEVICE_TABLE(virtio, id_table); |
258 | MODULE_DESCRIPTION("Virtio random number driver"); | |
259 | MODULE_LICENSE("GPL"); |