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| -rw-r--r-- | Documentation/make/headers_install.txt | 46 |
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diff --git a/Documentation/make/headers_install.txt b/Documentation/make/headers_install.txt new file mode 100644 index 000000000000..f2481cabffcb --- /dev/null +++ b/Documentation/make/headers_install.txt @@ -0,0 +1,46 @@ +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>. |