1 files changed, 265 insertions, 0 deletions
diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
new file mode 100644
index 000000000..353041173
--- /dev/null
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -0,0 +1,265 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Randomness driver for virtio
+ *  Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
+ */
+
+#include <asm/barrier.h>
+#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 hwrng_register_done;
+	bool hwrng_removed;
+	/* data transfer */
+	struct completion have_data;
+	unsigned int data_avail;
+	unsigned int data_idx;
+	/* 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;
+	unsigned int len;
+
+	/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
+	if (!virtqueue_get_buf(vi->vq, &len))
+		return;
+
+	smp_store_release(&vi->data_avail, len);
+	complete(&vi->have_data);
+}
+
+static void request_entropy(struct virtrng_info *vi)
+{
+	struct scatterlist sg;
+
+	reinit_completion(&vi->have_data);
+	vi->data_idx = 0;
+
+	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 unsigned int copy_data(struct virtrng_info *vi, void *buf,
+			      unsigned int size)
+{
+	size = min_t(unsigned int, size, vi->data_avail);
+	memcpy(buf, vi->data + vi->data_idx, size);
+	vi->data_idx += size;
+	vi->data_avail -= size;
+	if (vi->data_avail == 0)
+		request_entropy(vi);
+	return size;
+}
+
+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;
+
+	read = 0;
+
+	/* copy available data */
+	if (smp_load_acquire(&vi->data_avail)) {
+		chunk = copy_data(vi, buf, size);
+		size -= chunk;
+		read += chunk;
+	}
+
+	if (!wait)
+		return read;
+
+	/* We have already copied available entropy,
+	 * so either size is 0 or data_avail is 0
+	 */
+	while (size != 0) {
+		/* data_avail is 0 but a request is pending */
+		ret = wait_for_completion_killable(&vi->have_data);
+		if (ret < 0)
+			return ret;
+		/* if vi->data_avail is 0, we have been interrupted
+		 * by a cleanup, but buffer stays in the queue
+		 */
+		if (vi->data_avail == 0)
+			return read;
+
+		chunk = copy_data(vi, buf + read, size);
+		size -= chunk;
+		read += chunk;
+	}
+
+	return read;
+}
+
+static void virtio_cleanup(struct hwrng *rng)
+{
+	struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
+
+	complete(&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;
+	}
+
+	virtio_device_ready(vdev);
+
+	/* we always have a pending entropy request */
+	request_entropy(vi);
+
+	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;
+	vi->data_idx = 0;
+	complete(&vi->have_data);
+	if (vi->hwrng_register_done)
+		hwrng_unregister(&vi->hwrng);
+	virtio_reset_device(vdev);
+	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");