|Exporting kernel headers for use by userspace
|The "make headers_install" command exports the kernel's header files in a
|form suitable for use by userspace programs.
|The linux kernel's exported header files describe the API for user space
|programs attempting to use kernel services. These kernel header files are
|used by the system's C library (such as glibc or uClibc) to define available
|system calls, as well as constants and structures to be used with these
|system calls. The C library's header files include the kernel header files
|from the "linux" subdirectory. The system's libc headers are usually
|installed at the default location /usr/include and the kernel headers in
|subdirectories under that (most notably /usr/include/linux and
|Kernel headers are backwards compatible, but not forwards compatible. This
|means that a program built against a C library using older kernel headers
|should run on a newer kernel (although it may not have access to new
|features), but a program built against newer kernel headers may not work on an
|The "make headers_install" command can be run in the top level directory of the
|kernel source code (or using a standard out-of-tree build). It takes two
| make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr/include
|ARCH indicates which architecture to produce headers for, and defaults to the
|current architecture. The linux/asm directory of the exported kernel headers
|is platform-specific, to see a complete list of supported architectures use
| ls -d include/asm-* | sed 's/.*-//'
|INSTALL_HDR_PATH indicates where to install the headers. It defaults to
|The command "make headers_install_all" exports headers for all architectures
|simultaneously. (This is mostly of interest to distribution maintainers,
|who create an architecture-independent tarball from the resulting include
|directory.) You also can use HDR_ARCH_LIST to specify list of architectures.
|Remember to provide the appropriate linux/asm directory via "mv" or "ln -s"
|before building a C library with headers exported this way.
|The kernel header export infrastructure is maintained by David Woodhouse