1Exporting kernel headers for use by userspace
   4The "make headers_install" command exports the kernel's header files in a
   5form suitable for use by userspace programs.
   7The linux kernel's exported header files describe the API for user space
   8programs attempting to use kernel services.  These kernel header files are
   9used by the system's C library (such as glibc or uClibc) to define available
  10system calls, as well as constants and structures to be used with these
  11system calls.  The C library's header files include the kernel header files
  12from the "linux" subdirectory.  The system's libc headers are usually
  13installed at the default location /usr/include and the kernel headers in
  14subdirectories under that (most notably /usr/include/linux and
  17Kernel headers are backwards compatible, but not forwards compatible.  This
  18means that a program built against a C library using older kernel headers
  19should run on a newer kernel (although it may not have access to new
  20features), but a program built against newer kernel headers may not work on an
  21older kernel.
  23The "make headers_install" command can be run in the top level directory of the
  24kernel source code (or using a standard out-of-tree build).  It takes two
  25optional arguments:
  27  make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr/include
  29ARCH indicates which architecture to produce headers for, and defaults to the
  30current architecture.  The linux/asm directory of the exported kernel headers
  31is platform-specific, to see a complete list of supported architectures use
  32the command:
  34  ls -d include/asm-* | sed 's/.*-//'
  36INSTALL_HDR_PATH indicates where to install the headers.  It defaults to
  39The command "make headers_install_all" exports headers for all architectures
  40simultaneously.  (This is mostly of interest to distribution maintainers,
  41who create an architecture-independent tarball from the resulting include
  42directory.)  You also can use HDR_ARCH_LIST to specify list of architectures.
  43Remember to provide the appropriate linux/asm directory via "mv" or "ln -s"
  44before building a C library with headers exported this way.
  46The kernel header export infrastructure is maintained by David Woodhouse
  48 kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.