Commit 82082856 authored by Dominik Brodowski's avatar Dominik Brodowski Committed by Herbert Xu
Browse files

hwrng: core - introduce rng_quality sysfs attribute 



The rng_quality sysfs attribute returns the quality setting for the
currently active hw_random device, in entropy bits per 1024 bits of
input. Storing a value between 0 and 1024 to this file updates this
estimate accordingly.

Based on the updates to the quality setting, the rngd kernel thread
may be stopped (if no hw_random device is trusted to return entropy),
may be started (if the quality setting is increased from zero), or
may use a different hw_random source (if that has higher quality
output).

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent f0fb6953

drivers/char/hw_random/core.c

+63 −1
Original line number Diff line number Diff line
@@ -44,7 +44,7 @@ static unsigned short default_quality; /* = 0; default to "off" */ 


module_param(current_quality, ushort, 0644);

MODULE_PARM_DESC(current_quality,

		 "current hwrng entropy estimation per 1024 bits of input -- obsolete");

		 "current hwrng entropy estimation per 1024 bits of input -- obsolete, use rng_quality instead");

module_param(default_quality, ushort, 0644);

MODULE_PARM_DESC(default_quality,

		 "default entropy content of hwrng per 1024 bits of input");
@@ -402,14 +402,76 @@ static ssize_t rng_selected_show(struct device *dev, 
	return sysfs_emit(buf, "%d\n", cur_rng_set_by_user);

}



static ssize_t rng_quality_show(struct device *dev,

				struct device_attribute *attr,

				char *buf)

{

	ssize_t ret;

	struct hwrng *rng;



	rng = get_current_rng();

	if (IS_ERR(rng))

		return PTR_ERR(rng);



	if (!rng) /* no need to put_rng */

		return -ENODEV;



	ret = sysfs_emit(buf, "%hu\n", rng->quality);

	put_rng(rng);



	return ret;

}



static ssize_t rng_quality_store(struct device *dev,

				 struct device_attribute *attr,

				 const char *buf, size_t len)

{

	u16 quality;

	int ret = -EINVAL;



	if (len < 2)

		return -EINVAL;



	ret = mutex_lock_interruptible(&rng_mutex);

	if (ret)

		return -ERESTARTSYS;



	ret = kstrtou16(buf, 0, &quality);

	if (ret || quality > 1024) {

		ret = -EINVAL;

		goto out;

	}



	if (!current_rng) {

		ret = -ENODEV;

		goto out;

	}



	current_rng->quality = quality;

	current_quality = quality; /* obsolete */



	/* the best available RNG may have changed */

	ret = enable_best_rng();



	/* start/stop rngd if necessary */

	if (current_rng)

		hwrng_manage_rngd(current_rng);



out:

	mutex_unlock(&rng_mutex);

	return ret ? ret : len;

}



static DEVICE_ATTR_RW(rng_current);

static DEVICE_ATTR_RO(rng_available);

static DEVICE_ATTR_RO(rng_selected);

static DEVICE_ATTR_RW(rng_quality);



static struct attribute *rng_dev_attrs[] = {

	&dev_attr_rng_current.attr,

	&dev_attr_rng_available.attr,

	&dev_attr_rng_selected.attr,

	&dev_attr_rng_quality.attr,

	NULL

};