svn commit: r346250 - in head: share/man/man4 share/man/man9 sys/dev/random sys/kern sys/libkern sys/sys

[Conrad Meyer]

On Tue, Apr 16, 2019 at 7:24 AM Justin Hibbits <chmeeedalf at gmail.com> wrote:
>
> Hi Conrad,
> ...
> [Power] does use bsdinstall to install.  How is entropy loaded at startup,
> which causes the problem noted in github?

There are a couple very early load sources.  loader(8) will load
early-boot entropy from /boot/entropy and pass it to the kernel as a
fake module (entropy_cache_load in loader.conf(5)), similar to
cpu_microcode early load.

The fallback option is random(4) itself groping into the filesystem
during early auto-conf (SI_SUB_RANDOM:SI_ORDER_FOURTH, IIRC) to access
/boot/entropy directly.

> If it's loaded before
> filesystems get mounted, that could be a problem for us, because /boot
> is on a different filesystem (msdosfs, to be read by petitboot).
> Petitboot also does not have a way to preload modules, so all we have
> at startup, until spawning init, is the kernel.

Yes, that seems potentially problematic.  Can the Power kernel access
the non-msdosfs root filesystem?  Let's follow-up offline about
PPC-specific early entropy seeding.  I would much prefer we figure out
a way to provide early entropy to Power than disabling or crippling
every early random consumer on the arch.  Do you know what the Linux
folks do?

On Power with darn, we could probably just spin in SI_ORDER_FOURTH
until we have enough darn output to seed random.  Similar for x86 CI
images, I guess; though they do not have the loader problem, some
people have non-bsdinstall installation methods.

Thanks,
Conrad