[Arm-dev] rng-tools missing and /dev/hwrng without driver

Hi,

today I will report a problem that is released to ipa-server. This server contains a certificate authority and such service need many entropy. The default on CentOS 7 on a Banana PI is not enough, i.e. $(cat /proc/sys/kernel/random/entropy_avail) is less than 1000.

I have solved this in meantime by installing and enabling of haveged from the EPEL repository. Normally it would be done by installing the rng-tools. But there are two problems:
1. The rng-tools was not in the repositories, so I have downloaded rng-tools-5-8.fc24.armv7hl.rpm because this are the same version which is included in CentOS 7.3 for x86_64.
2. This rng-tools are usable but the daemon starts and stops immediately with the following error message:

# rngd -v
/dev/hwrng: No such device
/dev/tpm0: No such file or directory
No entropy sources found, exiting

This is not the problem of this binary it is a problem of the Kernel. /dev/hwrng exists and if I remove it then it reappears after reboot, but

# ls -l /dev/hwrng
crw-------. 1 root root 10, 183 1. Jan 1970 /dev/hwrng

# udevadm info -a -n /dev/hwrng

Udevadm info starts with the device specified by the devpath and then

walks up the chain of parent devices. It prints for every device

found, all possible attributes in the udev rules key format.

A rule to match, can be composed by the attributes of the device

and the attributes from one single parent device.

looking at device '/devices/virtual/misc/hw_random':

KERNEL=="hw_random"

SUBSYSTEM=="misc"

DRIVER==""

ATTR{rng_current}=="none"

ATTR{rng_available}==""

there is no driver for this device. I have searched and found this link http://forum.lemaker.org/thread-23618-1-1.html which includes a link to the full story. If I read all right then on bananian /dev/hwrng appears only if the adapted or a more actual sun4i-ss.ko module is loaded (there is written: "module author has indicated this will be going into the mainline kernel shortly“). This module is also loaded on a Banana PI with current CentOS 7. So does the kernel of CentOS 7.3 for ARM32 include this patch and if yes why it does not work or otherwise why this device appears but has no driver?

TIA,
Silvio

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