47 lines
2.2 KiB
Text
47 lines
2.2 KiB
Text
|
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
|
||
|
|
/usr/include/asm).
|
||
|
|
|
||
|
|
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
|
||
|
|
older kernel.
|
||
|
|
|
||
|
|
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
|
||
|
|
optional arguments:
|
||
|
|
|
||
|
|
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
|
||
|
|
the command:
|
||
|
|
|
||
|
|
ls -d include/asm-* | sed 's/.*-//'
|
||
|
|
|
||
|
|
INSTALL_HDR_PATH indicates where to install the headers. It defaults to
|
||
|
|
"./usr/include".
|
||
|
|
|
||
|
|
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.) 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
|
||
|
|
<dwmw2@infradead.org>.
|