Based on kernel version 3.9. Page generated on 2013-05-02 23:10 EST.
1 Exporting kernel headers for use by userspace 2 ============================================= 3 4 The "make headers_install" command exports the kernel's header files in a 5 form suitable for use by userspace programs. 6 7 The linux kernel's exported header files describe the API for user space 8 programs attempting to use kernel services. These kernel header files are 9 used by the system's C library (such as glibc or uClibc) to define available 10 system calls, as well as constants and structures to be used with these 11 system calls. The C library's header files include the kernel header files 12 from the "linux" subdirectory. The system's libc headers are usually 13 installed at the default location /usr/include and the kernel headers in 14 subdirectories under that (most notably /usr/include/linux and 15 /usr/include/asm). 16 17 Kernel headers are backwards compatible, but not forwards compatible. This 18 means that a program built against a C library using older kernel headers 19 should run on a newer kernel (although it may not have access to new 20 features), but a program built against newer kernel headers may not work on an 21 older kernel. 22 23 The "make headers_install" command can be run in the top level directory of the 24 kernel source code (or using a standard out-of-tree build). It takes two 25 optional arguments: 26 27 make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr/include 28 29 ARCH indicates which architecture to produce headers for, and defaults to the 30 current architecture. The linux/asm directory of the exported kernel headers 31 is platform-specific, to see a complete list of supported architectures use 32 the command: 33 34 ls -d include/asm-* | sed 's/.*-//' 35 36 INSTALL_HDR_PATH indicates where to install the headers. It defaults to 37 "./usr/include". 38 39 The command "make headers_install_all" exports headers for all architectures 40 simultaneously. (This is mostly of interest to distribution maintainers, 41 who create an architecture-independent tarball from the resulting include 42 directory.) You also can use HDR_ARCH_LIST to specify list of architectures. 43 Remember to provide the appropriate linux/asm directory via "mv" or "ln -s" 44 before building a C library with headers exported this way. 45 46 The kernel header export infrastructure is maintained by David Woodhouse 47 <firstname.lastname@example.org>.