39ceda5ce1
Pull Kbuild updates from Masahiro Yamada:
- remove headers_{install,check}_all targets
- remove unreasonable 'depends on !UML' from CONFIG_SAMPLES
- re-implement 'make headers_install' more cleanly
- add new header-test-y syntax to compile-test headers
- compile-test exported headers to ensure they are compilable in
user-space
- compile-test headers under include/ to ensure they are self-contained
- remove -Waggregate-return, -Wno-uninitialized, -Wno-unused-value
flags
- add -Werror=unknown-warning-option for Clang
- add 128-bit built-in types support to genksyms
- fix missed rebuild of modules.builtin
- propagate 'No space left on device' error in fixdep to Make
- allow Clang to use its integrated assembler
- improve some coccinelle scripts
- add a new flag KBUILD_ABS_SRCTREE to request Kbuild to use absolute
path for $(srctree).
- do not ignore errors when compression utility is missing
- misc cleanups
* tag 'kbuild-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (49 commits)
kbuild: use -- separater intead of $(filter-out ...) for cc-cross-prefix
kbuild: Inform user to pass ARCH= for make mrproper
kbuild: fix compression errors getting ignored
kbuild: add a flag to force absolute path for srctree
kbuild: replace KBUILD_SRCTREE with boolean building_out_of_srctree
kbuild: remove src and obj from the top Makefile
scripts/tags.sh: remove unused environment variables from comments
scripts/tags.sh: drop SUBARCH support for ARM
kbuild: compile-test kernel headers to ensure they are self-contained
kheaders: include only headers into kheaders_data.tar.xz
kheaders: remove meaningless -R option of 'ls'
kbuild: support header-test-pattern-y
kbuild: do not create wrappers for header-test-y
kbuild: compile-test exported headers to ensure they are self-contained
init/Kconfig: add CONFIG_CC_CAN_LINK
kallsyms: exclude kasan local symbols on s390
kbuild: add more hints about SUBDIRS replacement
coccinelle: api/stream_open: treat all wait_.*() calls as blocking
coccinelle: put_device: Add a cast to an expression for an assignment
coccinelle: put_device: Adjust a message construction
...
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=============================================
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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
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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".
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An 'include' directory is automatically created inside INSTALL_HDR_PATH and
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headers are installed in 'INSTALL_HDR_PATH/include'.
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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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