// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Randomness driver for virtio
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* Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
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*/
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#include <asm/barrier.h>
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#include <linux/err.h>
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#include <linux/hw_random.h>
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#include <linux/scatterlist.h>
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#include <linux/spinlock.h>
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#include <linux/virtio.h>
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#include <linux/virtio_rng.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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static DEFINE_IDA(rng_index_ida);
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struct virtrng_info {
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struct hwrng hwrng;
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struct virtqueue *vq;
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char name[25];
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int index;
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bool hwrng_register_done;
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bool hwrng_removed;
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/* data transfer */
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struct completion have_data;
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unsigned int data_avail;
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unsigned int data_idx;
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/* minimal size returned by rng_buffer_size() */
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#if SMP_CACHE_BYTES < 32
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u8 data[32];
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#else
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u8 data[SMP_CACHE_BYTES];
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#endif
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};
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static void random_recv_done(struct virtqueue *vq)
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{
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struct virtrng_info *vi = vq->vdev->priv;
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unsigned int len;
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/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
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if (!virtqueue_get_buf(vi->vq, &len))
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return;
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smp_store_release(&vi->data_avail, len);
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complete(&vi->have_data);
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}
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static void request_entropy(struct virtrng_info *vi)
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{
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struct scatterlist sg;
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reinit_completion(&vi->have_data);
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vi->data_idx = 0;
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sg_init_one(&sg, vi->data, sizeof(vi->data));
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/* There should always be room for one buffer. */
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virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL);
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virtqueue_kick(vi->vq);
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}
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static unsigned int copy_data(struct virtrng_info *vi, void *buf,
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unsigned int size)
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{
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size = min_t(unsigned int, size, vi->data_avail);
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memcpy(buf, vi->data + vi->data_idx, size);
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vi->data_idx += size;
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vi->data_avail -= size;
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if (vi->data_avail == 0)
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request_entropy(vi);
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return size;
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}
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static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
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{
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int ret;
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struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
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unsigned int chunk;
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size_t read;
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if (vi->hwrng_removed)
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return -ENODEV;
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read = 0;
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/* copy available data */
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if (smp_load_acquire(&vi->data_avail)) {
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chunk = copy_data(vi, buf, size);
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size -= chunk;
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read += chunk;
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}
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if (!wait)
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return read;
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/* We have already copied available entropy,
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* so either size is 0 or data_avail is 0
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*/
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while (size != 0) {
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/* data_avail is 0 but a request is pending */
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ret = wait_for_completion_killable(&vi->have_data);
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if (ret < 0)
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return ret;
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/* if vi->data_avail is 0, we have been interrupted
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* by a cleanup, but buffer stays in the queue
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*/
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if (vi->data_avail == 0)
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return read;
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chunk = copy_data(vi, buf + read, size);
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size -= chunk;
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read += chunk;
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}
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return read;
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}
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static void virtio_cleanup(struct hwrng *rng)
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{
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struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
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complete(&vi->have_data);
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}
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static int probe_common(struct virtio_device *vdev)
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{
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int err, index;
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struct virtrng_info *vi = NULL;
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vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
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if (!vi)
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return -ENOMEM;
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vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
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if (index < 0) {
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err = index;
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goto err_ida;
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}
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sprintf(vi->name, "virtio_rng.%d", index);
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init_completion(&vi->have_data);
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vi->hwrng = (struct hwrng) {
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.read = virtio_read,
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.cleanup = virtio_cleanup,
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.priv = (unsigned long)vi,
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.name = vi->name,
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.quality = 1000,
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};
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vdev->priv = vi;
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/* We expect a single virtqueue. */
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vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
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if (IS_ERR(vi->vq)) {
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err = PTR_ERR(vi->vq);
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goto err_find;
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}
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/* we always have a pending entropy request */
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request_entropy(vi);
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return 0;
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err_find:
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ida_simple_remove(&rng_index_ida, index);
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err_ida:
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kfree(vi);
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return err;
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}
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static void remove_common(struct virtio_device *vdev)
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{
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struct virtrng_info *vi = vdev->priv;
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vi->hwrng_removed = true;
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vi->data_avail = 0;
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vi->data_idx = 0;
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complete(&vi->have_data);
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vdev->config->reset(vdev);
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if (vi->hwrng_register_done)
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hwrng_unregister(&vi->hwrng);
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vdev->config->del_vqs(vdev);
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ida_simple_remove(&rng_index_ida, vi->index);
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kfree(vi);
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}
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static int virtrng_probe(struct virtio_device *vdev)
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{
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return probe_common(vdev);
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}
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static void virtrng_remove(struct virtio_device *vdev)
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{
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remove_common(vdev);
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}
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static void virtrng_scan(struct virtio_device *vdev)
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{
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struct virtrng_info *vi = vdev->priv;
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int err;
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err = hwrng_register(&vi->hwrng);
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if (!err)
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vi->hwrng_register_done = true;
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}
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#ifdef CONFIG_PM_SLEEP
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static int virtrng_freeze(struct virtio_device *vdev)
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{
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remove_common(vdev);
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return 0;
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}
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static int virtrng_restore(struct virtio_device *vdev)
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{
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int err;
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err = probe_common(vdev);
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if (!err) {
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struct virtrng_info *vi = vdev->priv;
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/*
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* Set hwrng_removed to ensure that virtio_read()
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* does not block waiting for data before the
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* registration is complete.
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*/
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vi->hwrng_removed = true;
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err = hwrng_register(&vi->hwrng);
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if (!err) {
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vi->hwrng_register_done = true;
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vi->hwrng_removed = false;
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}
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}
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return err;
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}
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#endif
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static const struct virtio_device_id id_table[] = {
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{ VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
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{ 0 },
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};
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static struct virtio_driver virtio_rng_driver = {
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.driver.name = KBUILD_MODNAME,
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.driver.owner = THIS_MODULE,
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.id_table = id_table,
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.probe = virtrng_probe,
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.remove = virtrng_remove,
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.scan = virtrng_scan,
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#ifdef CONFIG_PM_SLEEP
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.freeze = virtrng_freeze,
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.restore = virtrng_restore,
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#endif
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};
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module_virtio_driver(virtio_rng_driver);
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MODULE_DEVICE_TABLE(virtio, id_table);
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MODULE_DESCRIPTION("Virtio random number driver");
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MODULE_LICENSE("GPL");
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