[PATCH] Add new generic HW RNG core

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 370 insertions, 0 deletions

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
new file mode 100644
index 00000000000..fa4a245127a
--- /dev/null
+++ b/drivers/char/hw_random/Kconfig
@@ -0,0 +1,11 @@
+#
+# Hardware Random Number Generator (RNG) configuration
+#
+
+config HW_RANDOM
+	bool "Hardware Random Number Generator Core support"
+	default y
+	---help---
+	  Hardware Random Number Generator Core infrastructure.
+
+	  If unsure, say Y.
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
new file mode 100644
index 00000000000..aa752af468c
--- /dev/null
+++ b/drivers/char/hw_random/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for HW Random Number Generator (RNG) device drivers.
+#
+
+obj-$(CONFIG_HW_RANDOM) += core.o
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
new file mode 100644
index 00000000000..88b026639f1
--- /dev/null
+++ b/drivers/char/hw_random/core.c
@@ -0,0 +1,354 @@
+/*
+        Added support for the AMD Geode LX RNG
+	(c) Copyright 2004-2005 Advanced Micro Devices, Inc.
+
+	derived from
+
+ 	Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
+	(c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
+
+ 	derived from
+
+        Hardware driver for the AMD 768 Random Number Generator (RNG)
+        (c) Copyright 2001 Red Hat Inc <alan@redhat.com>
+
+ 	derived from
+
+	Hardware driver for Intel i810 Random Number Generator (RNG)
+	Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
+	Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
+
+	Added generic RNG API
+	Copyright 2006 Michael Buesch <mbuesch@freenet.de>
+	Copyright 2005 (c) MontaVista Software, Inc.
+
+	Please read Documentation/hw_random.txt for details on use.
+
+	----------------------------------------------------------
+	This software may be used and distributed according to the terms
+        of the GNU General Public License, incorporated herein by reference.
+
+ */
+
+
+#include <linux/device.h>
+#include <linux/hw_random.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/miscdevice.h>
+#include <linux/delay.h>
+#include <asm/uaccess.h>
+
+
+#define RNG_MODULE_NAME		"hw_random"
+#define PFX			RNG_MODULE_NAME ": "
+#define RNG_MISCDEV_MINOR	183 /* official */
+
+
+static struct hwrng *current_rng;
+static LIST_HEAD(rng_list);
+static DEFINE_MUTEX(rng_mutex);
+
+
+static inline int hwrng_init(struct hwrng *rng)
+{
+	if (!rng->init)
+		return 0;
+	return rng->init(rng);
+}
+
+static inline void hwrng_cleanup(struct hwrng *rng)
+{
+	if (rng && rng->cleanup)
+		rng->cleanup(rng);
+}
+
+static inline int hwrng_data_present(struct hwrng *rng)
+{
+	if (!rng->data_present)
+		return 1;
+	return rng->data_present(rng);
+}
+
+static inline int hwrng_data_read(struct hwrng *rng, u32 *data)
+{
+	return rng->data_read(rng, data);
+}
+
+
+static int rng_dev_open(struct inode *inode, struct file *filp)
+{
+	/* enforce read-only access to this chrdev */
+	if ((filp->f_mode & FMODE_READ) == 0)
+		return -EINVAL;
+	if (filp->f_mode & FMODE_WRITE)
+		return -EINVAL;
+	return 0;
+}
+
+static ssize_t rng_dev_read(struct file *filp, char __user *buf,
+			    size_t size, loff_t *offp)
+{
+	u32 data;
+	ssize_t ret = 0;
+	int i, err = 0;
+	int data_present;
+	int bytes_read;
+
+	while (size) {
+		err = -ERESTARTSYS;
+		if (mutex_lock_interruptible(&rng_mutex))
+			goto out;
+		if (!current_rng) {
+			mutex_unlock(&rng_mutex);
+			err = -ENODEV;
+			goto out;
+		}
+		if (filp->f_flags & O_NONBLOCK) {
+			data_present = hwrng_data_present(current_rng);
+		} else {
+			/* Some RNG require some time between data_reads to gather
+			 * new entropy. Poll it.
+			 */
+			for (i = 0; i < 20; i++) {
+				data_present = hwrng_data_present(current_rng);
+				if (data_present)
+					break;
+				udelay(10);
+			}
+		}
+		bytes_read = 0;
+		if (data_present)
+			bytes_read = hwrng_data_read(current_rng, &data);
+		mutex_unlock(&rng_mutex);
+
+		err = -EAGAIN;
+		if (!bytes_read && (filp->f_flags & O_NONBLOCK))
+			goto out;
+
+		err = -EFAULT;
+		while (bytes_read && size) {
+			if (put_user((u8)data, buf++))
+				goto out;
+			size--;
+			ret++;
+			bytes_read--;
+			data >>= 8;
+		}
+
+		if (need_resched())
+			schedule_timeout_interruptible(1);
+		err = -ERESTARTSYS;
+		if (signal_pending(current))
+			goto out;
+	}
+out:
+	return ret ? : err;
+}
+
+
+static struct file_operations rng_chrdev_ops = {
+	.owner		= THIS_MODULE,
+	.open		= rng_dev_open,
+	.read		= rng_dev_read,
+};
+
+static struct miscdevice rng_miscdev = {
+	.minor		= RNG_MISCDEV_MINOR,
+	.name		= RNG_MODULE_NAME,
+	.fops		= &rng_chrdev_ops,
+};
+
+
+static ssize_t hwrng_attr_current_store(struct class_device *class,
+					const char *buf, size_t len)
+{
+	int err;
+	struct hwrng *rng;
+
+	err = mutex_lock_interruptible(&rng_mutex);
+	if (err)
+		return -ERESTARTSYS;
+	err = -ENODEV;
+	list_for_each_entry(rng, &rng_list, list) {
+		if (strcmp(rng->name, buf) == 0) {
+			if (rng == current_rng) {
+				err = 0;
+				break;
+			}
+			err = hwrng_init(rng);
+			if (err)
+				break;
+			hwrng_cleanup(current_rng);
+			current_rng = rng;
+			err = 0;
+			break;
+		}
+	}
+	mutex_unlock(&rng_mutex);
+
+	return err ? : len;
+}
+
+static ssize_t hwrng_attr_current_show(struct class_device *class,
+				       char *buf)
+{
+	int err;
+	ssize_t ret;
+	const char *name = "none";
+
+	err = mutex_lock_interruptible(&rng_mutex);
+	if (err)
+		return -ERESTARTSYS;
+	if (current_rng)
+		name = current_rng->name;
+	ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
+	mutex_unlock(&rng_mutex);
+
+	return ret;
+}
+
+static ssize_t hwrng_attr_available_show(struct class_device *class,
+					 char *buf)
+{
+	int err;
+	ssize_t ret = 0;
+	struct hwrng *rng;
+
+	err = mutex_lock_interruptible(&rng_mutex);
+	if (err)
+		return -ERESTARTSYS;
+	buf[0] = '\0';
+	list_for_each_entry(rng, &rng_list, list) {
+		strncat(buf, rng->name, PAGE_SIZE - ret - 1);
+		ret += strlen(rng->name);
+		strncat(buf, " ", PAGE_SIZE - ret - 1);
+		ret++;
+	}
+	strncat(buf, "\n", PAGE_SIZE - ret - 1);
+	ret++;
+	mutex_unlock(&rng_mutex);
+
+	return ret;
+}
+
+static CLASS_DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
+			 hwrng_attr_current_show,
+			 hwrng_attr_current_store);
+static CLASS_DEVICE_ATTR(rng_available, S_IRUGO,
+			 hwrng_attr_available_show,
+			 NULL);
+
+
+static void unregister_miscdev(void)
+{
+	class_device_remove_file(rng_miscdev.class,
+				 &class_device_attr_rng_available);
+	class_device_remove_file(rng_miscdev.class,
+				 &class_device_attr_rng_current);
+	misc_deregister(&rng_miscdev);
+}
+
+static int register_miscdev(void)
+{
+	int err;
+
+	err = misc_register(&rng_miscdev);
+	if (err)
+		goto out;
+	err = class_device_create_file(rng_miscdev.class,
+				       &class_device_attr_rng_current);
+	if (err)
+		goto err_misc_dereg;
+	err = class_device_create_file(rng_miscdev.class,
+				       &class_device_attr_rng_available);
+	if (err)
+		goto err_remove_current;
+out:
+	return err;
+
+err_remove_current:
+	class_device_remove_file(rng_miscdev.class,
+				 &class_device_attr_rng_current);
+err_misc_dereg:
+	misc_deregister(&rng_miscdev);
+	goto out;
+}
+
+int hwrng_register(struct hwrng *rng)
+{
+	int must_register_misc;
+	int err = -EINVAL;
+	struct hwrng *old_rng, *tmp;
+
+	if (rng->name == NULL ||
+	    rng->data_read == NULL)
+		goto out;
+
+	mutex_lock(&rng_mutex);
+
+	/* Must not register two RNGs with the same name. */
+	err = -EEXIST;
+	list_for_each_entry(tmp, &rng_list, list) {
+		if (strcmp(tmp->name, rng->name) == 0)
+			goto out_unlock;
+	}
+
+	must_register_misc = (current_rng == NULL);
+	old_rng = current_rng;
+	if (!old_rng) {
+		err = hwrng_init(rng);
+		if (err)
+			goto out_unlock;
+		current_rng = rng;
+	}
+	err = 0;
+	if (must_register_misc) {
+		err = register_miscdev();
+		if (err) {
+			if (!old_rng) {
+				hwrng_cleanup(rng);
+				current_rng = NULL;
+			}
+			goto out_unlock;
+		}
+	}
+	INIT_LIST_HEAD(&rng->list);
+	list_add_tail(&rng->list, &rng_list);
+out_unlock:
+	mutex_unlock(&rng_mutex);
+out:
+	return err;
+}
+EXPORT_SYMBOL_GPL(hwrng_register);
+
+void hwrng_unregister(struct hwrng *rng)
+{
+	int err;
+
+	mutex_lock(&rng_mutex);
+
+	list_del(&rng->list);
+	if (current_rng == rng) {
+		hwrng_cleanup(rng);
+		if (list_empty(&rng_list)) {
+			current_rng = NULL;
+		} else {
+			current_rng = list_entry(rng_list.prev, struct hwrng, list);
+			err = hwrng_init(current_rng);
+			if (err)
+				current_rng = NULL;
+		}
+	}
+	if (list_empty(&rng_list))
+		unregister_miscdev();
+
+	mutex_unlock(&rng_mutex);
+}
+EXPORT_SYMBOL_GPL(hwrng_unregister);
+
+
+MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
+MODULE_LICENSE("GPL");