@SuperFloppies The VDSO as currently implemented in the #FreeBSD linuxulator doesn't like ASLR applied to it. It's implemented in such a way that making it ASLR-safe would take a non-trivial amount of work.
So, you have to use secadm to disable ASLR on the linux application.
I'm disinterested in supporting the linuxulator, so patches to add that support would need to come from the community.