47 lines
2.2 KiB
Plaintext
47 lines
2.2 KiB
Plaintext
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Exporting kernel headers for use by userspace
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=============================================
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The "make headers_install" command exports the kernel's header files in a
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form suitable for use by userspace programs.
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The linux kernel's exported header files describe the API for user space
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programs attempting to use kernel services. These kernel header files are
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used by the system's C library (such as glibc or uClibc) to define available
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system calls, as well as constants and structures to be used with these
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system calls. The C library's header files include the kernel header files
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from the "linux" subdirectory. The system's libc headers are usually
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installed at the default location /usr/include and the kernel headers in
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subdirectories under that (most notably /usr/include/linux and
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/usr/include/asm).
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Kernel headers are backwards compatible, but not forwards compatible. This
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means that a program built against a C library using older kernel headers
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should run on a newer kernel (although it may not have access to new
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features), but a program built against newer kernel headers may not work on an
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older kernel.
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The "make headers_install" command can be run in the top level directory of the
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kernel source code (or using a standard out-of-tree build). It takes two
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optional arguments:
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make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr/include
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ARCH indicates which architecture to produce headers for, and defaults to the
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current architecture. The linux/asm directory of the exported kernel headers
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is platform-specific, to see a complete list of supported architectures use
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the command:
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ls -d include/asm-* | sed 's/.*-//'
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INSTALL_HDR_PATH indicates where to install the headers. It defaults to
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"./usr/include".
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The command "make headers_install_all" exports headers for all architectures
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simultaneously. (This is mostly of interest to distribution maintainers,
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who create an architecture-independent tarball from the resulting include
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directory.) Remember to provide the appropriate linux/asm directory via "mv"
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or "ln -s" before building a C library with headers exported this way.
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The kernel header export infrastructure is maintained by David Woodhouse
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<dwmw2@infradead.org>.
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