/usr/src/linux-headers-3.19.0-42-generic/tools is in linux-headers-3.19.0-42-generic 3.19.0-42.48~14.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/src/linux-headers-3.19.0-42-generic/../linux-headers-3.19.0-42/tools