170 lines
3.6 KiB
C
170 lines
3.6 KiB
C
/*
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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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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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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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static struct virtqueue *vq;
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static unsigned int data_avail;
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static DECLARE_COMPLETION(have_data);
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static bool busy;
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static void random_recv_done(struct virtqueue *vq)
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{
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/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
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if (!virtqueue_get_buf(vq, &data_avail))
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return;
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complete(&have_data);
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}
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/* The host will fill any buffer we give it with sweet, sweet randomness. */
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static void register_buffer(u8 *buf, size_t size)
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{
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struct scatterlist sg;
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sg_init_one(&sg, buf, size);
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/* There should always be room for one buffer. */
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if (virtqueue_add_inbuf(vq, &sg, 1, buf, GFP_KERNEL) < 0)
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BUG();
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virtqueue_kick(vq);
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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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if (!busy) {
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busy = true;
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init_completion(&have_data);
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register_buffer(buf, size);
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}
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if (!wait)
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return 0;
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ret = wait_for_completion_killable(&have_data);
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if (ret < 0)
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return ret;
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busy = false;
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return data_avail;
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}
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static void virtio_cleanup(struct hwrng *rng)
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{
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if (busy)
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wait_for_completion(&have_data);
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}
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static struct hwrng virtio_hwrng = {
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.name = "virtio",
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.cleanup = virtio_cleanup,
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.read = virtio_read,
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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;
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if (vq) {
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/* We only support one device for now */
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return -EBUSY;
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}
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/* We expect a single virtqueue. */
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vq = virtio_find_single_vq(vdev, random_recv_done, "input");
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if (IS_ERR(vq)) {
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err = PTR_ERR(vq);
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vq = NULL;
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return err;
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}
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err = hwrng_register(&virtio_hwrng);
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if (err) {
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vdev->config->del_vqs(vdev);
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vq = NULL;
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return err;
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}
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return 0;
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}
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static void remove_common(struct virtio_device *vdev)
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{
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vdev->config->reset(vdev);
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busy = false;
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hwrng_unregister(&virtio_hwrng);
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vdev->config->del_vqs(vdev);
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vq = NULL;
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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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#ifdef CONFIG_PM
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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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return probe_common(vdev);
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}
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#endif
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static 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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#ifdef CONFIG_PM
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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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