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@xxxxxxxxxxxxxxxxxxx>
Cc: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
---
drivers/char/hw_random/core.c | 64 ++++++++++++++++++++++++++++++++++-
1 file changed, 63 insertions(+), 1 deletion(-)
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 8df102b39b35..71eafcc451e1 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -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
};
--
2.35.1
