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