New Generic HW RNG

Add a new generic H/W RNG core.

Signed-off-by Michael Buesch <[email protected]>

Index: hwrng/drivers/char/hw_random/core.c
===================================================================

drivers/char/hw_random/core.c new file +66 -0

@@ -0,0 +1,324 @@
+/*
+        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 <[email protected]>
+
+ 	derived from
+
+        Hardware driver for the AMD 768 Random Number Generator (RNG)
+        (c) Copyright 2001 Red Hat Inc <[email protected]>
+
+ 	derived from
+
+	Hardware driver for Intel i810 Random Number Generator (RNG)
+	Copyright 2000,2001 Jeff Garzik <[email protected]>
+	Copyright 2000,2001 Philipp Rumpf <[email protected]>
+
+	Added generic RNG API
+	Copyright 2006 Michael Buesch <[email protected]>
+	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 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)

drivers/char/hw_random/core.c new file +17 -0

+		}
+		have_data = 0;
+		if (current_rng->data_present == NULL ||
+		    current_rng->data_present(current_rng))
+			have_data = current_rng->data_read(current_rng, &data);
+		mutex_unlock(&rng_mutex);
+
+		while (have_data && size) {
+			if (put_user((u8)data, buf++)) {
+				ret = ret ? : -EFAULT;
+				break;
+			}
+			size--;
+			ret++;
+			have_data--;
+			data>>=8;
+		}

drivers/char/hw_random/core.c new file +35 -0

+			}
+			for (i = 0; i < 20; i++) {
+				if (current_rng->data_present == NULL ||
+				    current_rng->data_present(current_rng))
+					break;
+				udelay(10);
+			}
+			mutex_unlock(&rng_mutex);
+		}
+
+		if (signal_pending(current))
+			return ret ? : -ERESTARTSYS;
+	}
+	return ret;
+}
+
+
+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;

This does not handle the case of partial read correctly - the code should be

			return ret ? : -ERESTARTSYS;

drivers/char/hw_random/core.c line 79

Quoted 3 lines

drivers/char/hw_random/core.c new file +3 -0

+		if (!current_rng) {
+			mutex_unlock(&rng_mutex);
+			return -ENODEV;

The same problem here (although finding the RNG suddenly missing after we heve just read something from it is pretty unlikely).

Quoted 17 lines

drivers/char/hw_random/core.c new file +17 -0

+		}
+		have_data = 0;
+		if (current_rng->data_present == NULL ||
+		    current_rng->data_present(current_rng))
+			have_data = current_rng->data_read(current_rng, &data);
+		mutex_unlock(&rng_mutex);
+
+		while (have_data && size) {
+			if (put_user((u8)data, buf++)) {
+				ret = ret ? : -EFAULT;
+				break;
+			}
+			size--;
+			ret++;
+			have_data--;
+			data>>=8;
+		}

drivers/char/hw_random/core.c line 106

Quoted 10 lines

drivers/char/hw_random/core.c new file +10 -0

+
+		if (filp->f_flags & O_NONBLOCK)
+			return ret ? : -EAGAIN;
+
+		if (need_resched()) {
+			schedule_timeout_interruptible(1);
+		} else {
+			err = mutex_lock_interruptible(&rng_mutex);
+			if (err)
+				return err;

And here...

drivers/char/hw_random/core.c line 79

Quoted 3 lines

drivers/char/hw_random/core.c new file +3 -0

+			if (!current_rng) {
+				mutex_unlock(&rng_mutex);
+				return -ENODEV;

And here too.

drivers/char/hw_random/core.c line 154

Quoted 2 lines

drivers/char/hw_random/core.c new file +2 -0

+	list_for_each_entry(rng, &rng_list, list) {
+		if (strncmp(rng->name, buf, len) == 0) {

This will match if the passed string is just a prefix of rng->name. Apparently sysfs guarantees that the buffer passed to ->store will be NUL-terminated, so this should be just a strcmp().

drivers/char/hw_random/core.c line 161

Quoted 7 lines

drivers/char/hw_random/core.c new file +7 -0

+			if (rng->init) {
+				err = rng->init(rng);
+				if (err)
+					break;
+			}
+			if (current_rng && current_rng->cleanup)
+				current_rng->cleanup(current_rng);

What if rng == current_rng here (someone has written the same RNG name to the "store" attribute)? The lowlevel RNG driver should not have to handle nested init/cleanup calls.

Quoted 4 lines · you

This does not handle the case of partial read correctly - the code should be

			return ret ? : -ERESTARTSYS;

Quoted 5 lines · you

Quoted 4 lines · you

This does not handle the case of partial read correctly - the code should be

			return ret ? : -ERESTARTSYS;

Or, hm. Shouldn't we
return ret ? : err;

err is -EINTR

Quoted 10 lines · Michael Buesch

Quoted 5 lines · you

Quoted 4 lines · you

This does not handle the case of partial read correctly - the code should be

			return ret ? : -ERESTARTSYS;

Or, hm. Shouldn't we
return ret ? : err;

Quoted 1 line

err is -EINTR

-ERESTARTSYS is the proper return code for this case - the signal handling code will either convert it to EINTR for userspace, or restart the system call after handling the signal, depending on the state of the SA_RESTART flag set by sigaction().

Quoted 6 lines · you

drivers/char/hw_random/core.c line 154

Quoted 2 lines

drivers/char/hw_random/core.c new file +2 -0

+	list_for_each_entry(rng, &rng_list, list) {
+		if (strncmp(rng->name, buf, len) == 0) {

This will match if the passed string is just a prefix of rng->name. Apparently sysfs guarantees that the buffer passed to ->store will be NUL-terminated, so this should be just a strcmp().

I am not sure if it is guaranteed NUL terminated. Greg? But I will look into this.

Quoted 8 lines · Michael Buesch

Quoted 6 lines · you

drivers/char/hw_random/core.c line 154

Quoted 2 lines

drivers/char/hw_random/core.c new file +2 -0

+	list_for_each_entry(rng, &rng_list, list) {
+		if (strncmp(rng->name, buf, len) == 0) {

This will match if the passed string is just a prefix of rng->name. Apparently sysfs guarantees that the buffer passed to ->store will be NUL-terminated, so this should be just a strcmp().

Quoted 2 lines

I am not sure if it is guaranteed NUL terminated. Greg? But I will look into this.

Yes it will be.

Add a driver for the x86 RNG.
This driver is ported from the old hw_random.c

Quoted 2 lines · On Sun, 07 May 2006 13:35:16 +0200 Michael Buesch wrote:

Add a driver for the x86 RNG.
This driver is ported from the old hw_random.c

In fact, this is 4 completely different drivers - probably they should be split now?