This may be because sysprof user space is not running as root, or it
may be because the kernel is generating bogus addresses.
Generally, "No Map" means sysprof is seeing samples in memory regions
that are not in /proc/<pid>/maps
Actually, I seem to remember one cause of this: the vdso code creates
an unusual stackframe where the pointer to the previous frame is
stored in an unusual place. I think the sysprof kernel code needs to
take this into account, or alternatively send sufficient information
to userspace that it can figure it out itself.