HelenOS sources

abi/include/abi/ipc/ipc.h
kernel/generic/include/ipc/ipc.h
uspace/lib/c/include/ipc/ipc.h
uspace/lib/posix/include/libc/ipc/ipc.h
uspace/lib/usbvirt/include/usbvirt/ipc.h
HelenOS homepage, sources at GitHub