install/56921: sysinst fails to mount /boot when selecting "Use existing GPT partitions"

[mrg%eterna.com.au@localhost]

>Number:         56921
>Category:       install
>Synopsis:       sysinst fails to mount /boot when selecting "Use existing GPT partitions"
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jul 11 00:50:00 +0000 2022
>Originator:     matthew green
>Release:        NetBSD 9.99.98
>Organization:
people's front against (bozotic) www (softwar foundation)
>Environment:
System: NetBSD 9.99.98 (GENERIC64) #52: Sun Jul 10 16:29:05 PDT 2022 mrg%yesterday-when-i-was-mad.eterna23.net@localhost:/var/obj/evbarm-aarch64/usr/src/sys/arch/evbarm/compile/GENERIC64
Architecture: aarch64
Machine: evbarm
>Description:

	when the installation is interrupted mid-way and restarted, there
	are cases where /boot is not mounted before sets are extracted and
	thus this partition ends up empty and the system can't boot.

>How-To-Repeat:

	i built an evbarm64 release & iso-image, created an empty disk image
	for installation, and also a 3rd image with the release sets on them.
	i fired up qemu with the ISO and 2 disk images attached, it boots the
	ISO, and enters the installer.

	from this point i proceeded with a normal installation, but due to
	an error with the release sets image, i had to cancel and restart
	after the GPT was created, and the ffs (/) and msdos (/boot)
	partitions were made (but are empty.)

	i replaced the sets disk image, restarted, and the installation went
	ahead like normal.  i selected the "Use existing GPT partitions"
	option during partitioning, and then "Partition sizes ok" next, and
	then answered questions about mounting the sets and it extracted the
	sets and went through the final configuration steps.  i exited the
	installer, "halt -p", removed the installer ISO from the disk list
	and restarted qemu, but it fails to boot.  inspection of the /boot
	partition shows it is empty, and the contents are actually in the
	root file system.

	the only place that file systems are mounted that aren't root are
	the ones created by this instance of the installer is in the
	make_filesystems() function, which isn't used in this case (though
	perhaps it should be, since this is not an ugprade but a fresh
	installation.)

	i tried running an 'upgrade' afterwards, hoping it would mount /boot
	and update it, but it remains empty & non-bootable.  suspending
	sysinst while it is extracting sets shows that only /targetroot is
	mounted, not /targetroot/boot as well.

>Fix: