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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Randomness driver for virtio4 * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation5 */6 7#include <asm/barrier.h>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>14#include <linux/module.h>15#include <linux/slab.h>16 17static DEFINE_IDA(rng_index_ida);18 19struct virtrng_info {20 struct hwrng hwrng;21 struct virtqueue *vq;22 char name[25];23 int index;24 bool hwrng_register_done;25 bool hwrng_removed;26 /* data transfer */27 struct completion have_data;28 unsigned int data_avail;29 unsigned int data_idx;30 /* minimal size returned by rng_buffer_size() */31#if SMP_CACHE_BYTES < 3232 u8 data[32];33#else34 u8 data[SMP_CACHE_BYTES];35#endif36};37 38static void random_recv_done(struct virtqueue *vq)39{40 struct virtrng_info *vi = vq->vdev->priv;41 unsigned int len;42 43 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */44 if (!virtqueue_get_buf(vi->vq, &len))45 return;46 47 smp_store_release(&vi->data_avail, len);48 complete(&vi->have_data);49}50 51static void request_entropy(struct virtrng_info *vi)52{53 struct scatterlist sg;54 55 reinit_completion(&vi->have_data);56 vi->data_idx = 0;57 58 sg_init_one(&sg, vi->data, sizeof(vi->data));59 60 /* There should always be room for one buffer. */61 virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL);62 63 virtqueue_kick(vi->vq);64}65 66static 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;73 if (vi->data_avail == 0)74 request_entropy(vi);75 return size;76}77 78static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)79{80 int ret;81 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;82 unsigned int chunk;83 size_t read;84 85 if (vi->hwrng_removed)86 return -ENODEV;87 88 read = 0;89 90 /* copy available data */91 if (smp_load_acquire(&vi->data_avail)) {92 chunk = copy_data(vi, buf, size);93 size -= chunk;94 read += chunk;95 }96 97 if (!wait)98 return read;99 100 /* We have already copied available entropy,101 * so either size is 0 or data_avail is 0102 */103 while (size != 0) {104 /* data_avail is 0 but a request is pending */105 ret = wait_for_completion_killable(&vi->have_data);106 if (ret < 0)107 return ret;108 /* if vi->data_avail is 0, we have been interrupted109 * by a cleanup, but buffer stays in the queue110 */111 if (vi->data_avail == 0)112 return read;113 114 chunk = copy_data(vi, buf + read, size);115 size -= chunk;116 read += chunk;117 }118 119 return read;120}121 122static void virtio_cleanup(struct hwrng *rng)123{124 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;125 126 complete(&vi->have_data);127}128 129static int probe_common(struct virtio_device *vdev)130{131 int err, index;132 struct virtrng_info *vi = NULL;133 134 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);135 if (!vi)136 return -ENOMEM;137 138 vi->index = index = ida_alloc(&rng_index_ida, GFP_KERNEL);139 if (index < 0) {140 err = index;141 goto err_ida;142 }143 sprintf(vi->name, "virtio_rng.%d", index);144 init_completion(&vi->have_data);145 146 vi->hwrng = (struct hwrng) {147 .read = virtio_read,148 .cleanup = virtio_cleanup,149 .priv = (unsigned long)vi,150 .name = vi->name,151 };152 vdev->priv = vi;153 154 /* We expect a single virtqueue. */155 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");156 if (IS_ERR(vi->vq)) {157 err = PTR_ERR(vi->vq);158 goto err_find;159 }160 161 virtio_device_ready(vdev);162 163 /* we always have a pending entropy request */164 request_entropy(vi);165 166 return 0;167 168err_find:169 ida_free(&rng_index_ida, index);170err_ida:171 kfree(vi);172 return err;173}174 175static void remove_common(struct virtio_device *vdev)176{177 struct virtrng_info *vi = vdev->priv;178 179 vi->hwrng_removed = true;180 vi->data_avail = 0;181 vi->data_idx = 0;182 complete(&vi->have_data);183 if (vi->hwrng_register_done)184 hwrng_unregister(&vi->hwrng);185 virtio_reset_device(vdev);186 vdev->config->del_vqs(vdev);187 ida_free(&rng_index_ida, vi->index);188 kfree(vi);189}190 191static int virtrng_probe(struct virtio_device *vdev)192{193 return probe_common(vdev);194}195 196static void virtrng_remove(struct virtio_device *vdev)197{198 remove_common(vdev);199}200 201static 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 211static int virtrng_freeze(struct virtio_device *vdev)212{213 remove_common(vdev);214 return 0;215}216 217static int virtrng_restore(struct virtio_device *vdev)218{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 the228 * 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;239}240 241static const struct virtio_device_id id_table[] = {242 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },243 { 0 },244};245 246static struct virtio_driver virtio_rng_driver = {247 .driver.name = KBUILD_MODNAME,248 .id_table = id_table,249 .probe = virtrng_probe,250 .remove = virtrng_remove,251 .scan = virtrng_scan,252 .freeze = pm_sleep_ptr(virtrng_freeze),253 .restore = pm_sleep_ptr(virtrng_restore),254};255 256module_virtio_driver(virtio_rng_driver);257MODULE_DEVICE_TABLE(virtio, id_table);258MODULE_DESCRIPTION("Virtio random number driver");259MODULE_LICENSE("GPL");260