xnu | XNU kernel is part of the Darwin operating system

To install IOKit headers, see additional comments in [iokit/IOKit/Makefile](). XNU installs header files at the following locations -. Kernel.framework is used by kernel extensions.\ The System.framework and /usr/include are used by user level applications. \ The header files in framework’s PrivateHeaders are only available for Apple Internal Development . The directory containing the header file should have a Makefile that creates the list of files that should be installed at different locations. If you are adding the first header file in a directory, you will need to create Makefile similar to xnu/bsd/sys/Makefile. Add your header file to the correct file list depending on where you want to install it. The default locations where the header files are installed from each file list are -. The Makefile combines the file lists mentioned above into different install lists which are used by build system to install the header files. There are two types of install lists: machine-dependent and machine-independent. These lists are indicated by the presence of MD and MI in the build setting, respectively. If your header is architecture-specific, then you should use a machine-dependent install list (e.g. INSTALL_MD_LIST). If your header should be installed for all architectures, then you should use a machine-independent install list (e.g. INSTALL_MI_LIST). If the install list that you are interested does not exist, create it by adding the appropriate file lists. The default install lists, its member file lists and their default location are described below -. If you want to install the header file in a sub-directory of the paths described in (1), specify the directory name using two variables INSTALL_MI_DIR and EXPORT_MI_DIR as follows -. A single header file can exist at different locations using the steps mentioned above. However it might not be desirable to make all the code in the header file available at all the locations. For example, you want to export a function only to kernel level but not user level.
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/Headers
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders
$(DSTROOT)/usr/include/
$(DSTROOT)/System/Library/Frameworks/System.framework/PrivateHeaders
DATAFILES : To make header file available in user level - $(DSTROOT)/usr/include
PRIVATE_DATAFILES : To make header file available to Apple internal in user level - $(DSTROOT)/System/Library/Frameworks/System.framework/PrivateHeaders
KERNELFILES : To make header file available in kernel level - $(DSTROOT)/System/Library/Frameworks/Kernel.framework/Headers $(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders
PRIVATE_KERNELFILES : To make header file available to Apple internal for kernel extensions - $(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders
INSTALL_MI_LIST : Installs header file to a location that is available to everyone in user level. Locations - $(DSTROOT)/usr/include Definition - INSTALL_MI_LIST = ${DATAFILES}
INSTALL_MI_LCL_LIST : Installs header file to a location that is available for Apple internal in user level. Locations - $(DSTROOT)/System/Library/Frameworks/System.framework/PrivateHeaders Definition - INSTALL_MI_LCL_LIST = ${PRIVATE_DATAFILES}
INSTALL_KF_MI_LIST : Installs header file to location that is available to everyone for kernel extensions. Locations - $(DSTROOT)/System/Library/Frameworks/Kernel.framework/Headers Definition - INSTALL_KF_MI_LIST = ${KERNELFILES}
INSTALL_KF_MI_LCL_LIST : Installs header file to location that is available for Apple internal for kernel extensions. Locations - $(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders Definition - INSTALL_KF_MI_LCL_LIST = ${KERNELFILES} ${PRIVATE_KERNELFILES}
EXPORT_MI_LIST : Exports header file to all of xnu (bsd/, osfmk/, etc.) for compilation only. Does not install anything into the SDK. Definition - EXPORT_MI_LIST = ${KERNELFILES} ${PRIVATE_KERNELFILES}
PRIVATE : If defined, enclosed definitions are considered System Private Interfaces. These are visible within xnu and exposed in user/kernel headers installed within the AppleInternal "PrivateHeaders" sections of the System and Kernel frameworks.
KERNEL_PRIVATE : If defined, enclosed code is available to all of xnu kernel and Apple internal kernel extensions and omitted from user headers.
BSD_KERNEL_PRIVATE : If defined, enclosed code is visible exclusively within the xnu/bsd module.
MACH_KERNEL_PRIVATE: If defined, enclosed code is visible exclusively within the xnu/osfmk module.
XNU_KERNEL_PRIVATE: If defined, enclosed code is visible exclusively within xnu.
KERNEL : If defined, enclosed code is available within xnu and kernel extensions and is not visible in user level header files. Only the header files installed in following paths will have the code - $(DSTROOT)/System/Library/Frameworks/Kernel.framework/Headers $(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders