/usr/include/xenomai/asm-powerpc/ is in libxenomai-dev 2.6.4+dfsg-0.2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/xenomai/asm-powerpc/arith.h
/usr/include/xenomai/asm-powerpc/atomic.h
/usr/include/xenomai/asm-powerpc/atomic_asm.h
/usr/include/xenomai/asm-powerpc/bits/
/usr/include/xenomai/asm-powerpc/bits/bind.h
/usr/include/xenomai/asm-powerpc/bits/heap.h
/usr/include/xenomai/asm-powerpc/bits/init.h
/usr/include/xenomai/asm-powerpc/bits/intr.h
/usr/include/xenomai/asm-powerpc/bits/pod.h
/usr/include/xenomai/asm-powerpc/bits/sched.h
/usr/include/xenomai/asm-powerpc/bits/shadow.h
/usr/include/xenomai/asm-powerpc/bits/thread.h
/usr/include/xenomai/asm-powerpc/bits/timer.h
/usr/include/xenomai/asm-powerpc/calibration.h
/usr/include/xenomai/asm-powerpc/features.h
/usr/include/xenomai/asm-powerpc/fptest.h
/usr/include/xenomai/asm-powerpc/hal.h
/usr/include/xenomai/asm-powerpc/syscall.h
/usr/include/xenomai/asm-powerpc/system.h
/usr/include/xenomai/asm-powerpc/tsc.h
/usr/include/xenomai/asm-powerpc/wrappers.h