bin/55686: unaligned access / segmentation fault in ssh-keygen for ecdsa key on Alpha

[thorpej%me.com@localhost]

>Number:         55686
>Category:       bin
>Synopsis:       unaligned access / segmentation fault in ssh-keygen for ecdsa key on Alpha
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Sep 29 01:50:00 +0000 2020
>Originator:     Jason Thorpe
>Release:        9.99.73
>Organization:
RISCy Business
>Environment:
NetBSD alpha-vm 9.99.73 NetBSD 9.99.73 (GENERIC-$Revision: 1.410 $) #6: Mon Sep 28 16:07:03 PDT 2020  thorpej@stinky:/home/nbsd/src/sys/arch/alpha/compile/GENERIC alpha

Running inside Qemu.
>Description:
When generating the ecdsa, ssh-keygen has an unaligned access and crashes:

alpha-vm# /etc/rc.d/sshd start
[ 5820.5003139] pid 1458 (ssh-keygen): unaligned access: va=0x1ffffe617 pc=0x0 ra=0x3fffdc78fd4 sp=0x1ffffe590 op=ldq
[1]   Segmentation fault (core dumped) "${keygen}" -t "${type}" ${bitarg} -f "${f}" -...
Starting sshd.

Unaligned fix-up is enabled:

alpha-vm# sysctl machdep
machdep.root_device = wd0
machdep.unaligned_print = 1
machdep.unaligned_fix = 1
machdep.unaligned_sigbus = 0
machdep.booted_kernel = 
machdep.fp_sync_complete = 0
alpha-vm# 

The pc value is a little suspicious.  More investigation is warranted.
>How-To-Repeat:
See above.
>Fix:
Not (yet) provided.