Readd carrying on random seed between boots

This provides extra security for applications that blindly read from
/dev/urandom on boot without it being properly seeded first, which is a
concern for our Pine, as it generates relatively few entropy during
early boot.

In addition, if some misbehaved application thereafter insists on
reading from /dev/random, it will virtually have an endless supply of
random data via haveged.

However, applications concerned with good random numbers should use the
getrandom system call instead of the arguably bad designed /dev/random
and /dev/urandom interfaces, so these kind of workarounds would be
unnecessary.

board/common/linux.config

@@ -603,6 +603,7 @@ CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
 CONFIG_BOOTPARAM_HUNG_TASK_PANIC=y
 CONFIG_WQ_WATCHDOG=y
 # CONFIG_DEBUG_PREEMPT is not set
+CONFIG_WARN_ALL_UNSEEDED_RANDOM=y
 CONFIG_BUG_ON_DATA_CORRUPTION=y
 CONFIG_LATENCYTOP=y
 # CONFIG_FTRACE is not set

board/pinetainer/post-build.sh

@@ -1,7 +1,8 @@
 #!/bin/sh
 
-# Tweak network, dnsmasq, udev and haveged start order
+# Tweak network, dnsmasq, udev, haveged and urandom seed storage start order
 mv "${1:?}/etc/init.d/S40network" "${1:?}/etc/init.d/S03network.sh" 2>/dev/null || true
+mv "${1:?}/etc/init.d/S20urandom" "${1:?}/etc/init.d/S01urandom.sh" 2>/dev/null || true
 mv "${1:?}/etc/init.d/S80dnsmasq" "${1:?}/etc/init.d/S10dnsmasq.sh" 2>/dev/null || true
 mv "${1:?}/etc/init.d/S10udev" "${1:?}/etc/init.d/S90udev.sh" 2>/dev/null || true
 mv "${1:?}/etc/init.d/S21haveged" "${1:?}/etc/init.d/S01haveged.sh" 2>/dev/null || true

configs/pinetainer_defconfig

@@ -128,7 +128,6 @@ BR2_PACKAGE_TCPDUMP=y
 BR2_PACKAGE_UACME=y
 BR2_PACKAGE_UACME_UALPN=y
 BR2_PACKAGE_WGET=y
-# BR2_PACKAGE_URANDOM_SCRIPTS is not set
 BR2_PACKAGE_AT=y
 BR2_PACKAGE_LOGROTATE=y
 BR2_PACKAGE_QPRINT=y