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hwrng: core - introduce rng_quality sysfs attribute

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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: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Dominik Brodowski 2022-02-13 21:46:31 +01:00 committed by Herbert Xu
parent f0fb6953b3
commit 8208285632
1 changed files with 63 additions and 1 deletions
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64
drivers/char/hw_random/core.c
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@ -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
};