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Commit f7f510ec authored by Rusty Russell's avatar Rusty Russell
Browse files

virtio: An entropy device, as suggested by hpa. 



Note that by itself, having a "hardware" random generator does very
little: you should probably run "rngd" in your guest to feed this into
the kernel entropy pool.

Included:
	virtio_rng: dont use vmalloced addresses for virtio

	If virtio_rng is build as a module, random_data is an address
	in vmalloc space. As virtio expects guest real addresses, this
	can cause any kind of funny behaviour, so lets allocate
	random_data dynamically with kmalloc.

	Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 3ef53609

drivers/char/hw_random/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -112,3 +112,12 @@ config HW_RANDOM_PASEMI 


	  If unsure, say Y.



config HW_RANDOM_VIRTIO

	tristate "VirtIO Random Number Generator support"

	depends on HW_RANDOM && VIRTIO

	---help---

	  This driver provides kernel-side support for the virtual Random Number

	  Generator hardware.



	  To compile this driver as a module, choose M here: the

	  module will be called virtio-rng.  If unsure, say N.

drivers/char/hw_random/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -11,3 +11,4 @@ obj-$(CONFIG_HW_RANDOM_VIA) += via-rng.o 
obj-$(CONFIG_HW_RANDOM_IXP4XX) += ixp4xx-rng.o

obj-$(CONFIG_HW_RANDOM_OMAP) += omap-rng.o

obj-$(CONFIG_HW_RANDOM_PASEMI) += pasemi-rng.o

obj-$(CONFIG_HW_RANDOM_VIRTIO) += virtio-rng.o

drivers/char/hw_random/virtio-rng.c

0 → 100644
+155 −0
Original line number Diff line number Diff line 
/*

 * Randomness driver for virtio

 *  Copyright (C) 2007, 2008 Rusty Russell IBM Corporation

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; either version 2 of the License, or

 *  (at your option) any later version.

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *  GNU General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with this program; if not, write to the Free Software

 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA

 */

#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>



/* The host will fill any buffer we give it with sweet, sweet randomness.  We

 * give it 64 bytes at a time, and the hwrng framework takes it 4 bytes at a

 * time. */

#define RANDOM_DATA_SIZE 64



static struct virtqueue *vq;

static u32 *random_data;

static unsigned int data_left;

static DECLARE_COMPLETION(have_data);



static void random_recv_done(struct virtqueue *vq)

{

	int len;



	/* We never get spurious callbacks. */

	if (!vq->vq_ops->get_buf(vq, &len))

		BUG();



	data_left = len / sizeof(random_data[0]);

	complete(&have_data);

}



static void register_buffer(void)

{

	struct scatterlist sg;



	sg_init_one(&sg, random_data, RANDOM_DATA_SIZE);

	/* There should always be room for one buffer. */

	if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) != 0)

		BUG();

	vq->vq_ops->kick(vq);

}



/* At least we don't udelay() in a loop like some other drivers. */

static int virtio_data_present(struct hwrng *rng, int wait)

{

	if (data_left)

		return 1;



	if (!wait)

		return 0;



	wait_for_completion(&have_data);

	return 1;

}



/* virtio_data_present() must have succeeded before this is called. */

static int virtio_data_read(struct hwrng *rng, u32 *data)

{

	BUG_ON(!data_left);



	*data = random_data[--data_left];



	if (!data_left) {

		init_completion(&have_data);

		register_buffer();

	}

	return sizeof(*data);

}



static struct hwrng virtio_hwrng = {

	.name = "virtio",

	.data_present = virtio_data_present,

	.data_read = virtio_data_read,

};



static int virtrng_probe(struct virtio_device *vdev)

{

	int err;



	/* We expect a single virtqueue. */

	vq = vdev->config->find_vq(vdev, 0, random_recv_done);

	if (IS_ERR(vq))

		return PTR_ERR(vq);



	err = hwrng_register(&virtio_hwrng);

	if (err) {

		vdev->config->del_vq(vq);

		return err;

	}



	register_buffer();

	return 0;

}



static void virtrng_remove(struct virtio_device *vdev)

{

	vdev->config->reset(vdev);

	hwrng_unregister(&virtio_hwrng);

	vdev->config->del_vq(vq);

}



static struct virtio_device_id id_table[] = {

	{ VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },

	{ 0 },

};



static struct virtio_driver virtio_rng = {

	.driver.name =	KBUILD_MODNAME,

	.driver.owner =	THIS_MODULE,

	.id_table =	id_table,

	.probe =	virtrng_probe,

	.remove =	__devexit_p(virtrng_remove),

};



static int __init init(void)

{

	int err;



	random_data = kmalloc(RANDOM_DATA_SIZE, GFP_KERNEL);

	if (!random_data)

		return -ENOMEM;



	err = register_virtio_driver(&virtio_rng);

	if (err)

		kfree(random_data);

	return err;

}



static void __exit fini(void)

{

	kfree(random_data);

	unregister_virtio_driver(&virtio_rng);

}

module_init(init);

module_exit(fini);



MODULE_DEVICE_TABLE(virtio, id_table);

MODULE_DESCRIPTION("Virtio random number driver");

MODULE_LICENSE("GPL");

include/linux/virtio_rng.h

0 → 100644
+8 −0
Original line number Diff line number Diff line 
#ifndef _LINUX_VIRTIO_RNG_H

#define _LINUX_VIRTIO_RNG_H

#include <linux/virtio_config.h>



/* The ID for virtio_rng */

#define VIRTIO_ID_RNG	4



#endif /* _LINUX_VIRTIO_RNG_H */