Documentation/kbuild/kbuild.txt - maze/linux - Git at Google

 Output files

 modules.order
 --------------------------------------------------
 This file records the order in which modules appear in Makefiles. This
 is used by modprobe to deterministically resolve aliases that match
 multiple modules.

 modules.builtin
 --------------------------------------------------
 This file lists all modules that are built into the kernel. This is used
 by modprobe to not fail when trying to load something builtin.


 Environment variables

 KCPPFLAGS
 --------------------------------------------------
 Additional options to pass when preprocessing. The preprocessing options
 will be used in all cases where kbuild does preprocessing including
 building C files and assembler files.

 KAFLAGS
 --------------------------------------------------
 Additional options to the assembler (for built-in and modules).

 AFLAGS_MODULE
 --------------------------------------------------
 Addtional module specific options to use for $(AS).

 AFLAGS_KERNEL
 --------------------------------------------------
 Addtional options for $(AS) when used for assembler
 code for code that is compiled as built-in.

 KCFLAGS
 --------------------------------------------------
 Additional options to the C compiler (for built-in and modules).

 CFLAGS_KERNEL
 --------------------------------------------------
 Addtional options for $(CC) when used to compile
 code that is compiled as built-in.

 CFLAGS_MODULE
 --------------------------------------------------
 Addtional module specific options to use for $(CC).

 LDFLAGS_MODULE
 --------------------------------------------------
 Additional options used for $(LD) when linking modules.

 KBUILD_VERBOSE
 --------------------------------------------------
 Set the kbuild verbosity. Can be assigned same values as "V=...".
 See make help for the full list.
 Setting "V=..." takes precedence over KBUILD_VERBOSE.

 KBUILD_EXTMOD
 --------------------------------------------------
 Set the directory to look for the kernel source when building external
 modules.
 The directory can be specified in several ways:
 1) Use "M=..." on the command line
 2) Environment variable KBUILD_EXTMOD
 3) Environment variable SUBDIRS
 The possibilities are listed in the order they take precedence.
 Using "M=..." will always override the others.

 KBUILD_OUTPUT
 --------------------------------------------------
 Specify the output directory when building the kernel.
 The output directory can also be specified using "O=...".
 Setting "O=..." takes precedence over KBUILD_OUTPUT.

 KBUILD_DEBARCH
 --------------------------------------------------
 For the deb-pkg target, allows overriding the normal heuristics deployed by
 deb-pkg. Normally deb-pkg attempts to guess the right architecture based on
 the UTS_MACHINE variable, and on some architectures also the kernel config.
 The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian
 architecture.

 ARCH
 --------------------------------------------------
 Set ARCH to the architecture to be built.
 In most cases the name of the architecture is the same as the
 directory name found in the arch/ directory.
 But some architectures such as x86 and sparc have aliases.
 x86: i386 for 32 bit, x86_64 for 64 bit
 sparc: sparc for 32 bit, sparc64 for 64 bit

 CROSS_COMPILE
 --------------------------------------------------
 Specify an optional fixed part of the binutils filename.
 CROSS_COMPILE can be a part of the filename or the full path.

 CROSS_COMPILE is also used for ccache in some setups.

 CF
 --------------------------------------------------
 Additional options for sparse.
 CF is often used on the command-line like this:

     make CF=-Wbitwise C=2

 INSTALL_PATH
 --------------------------------------------------
 INSTALL_PATH specifies where to place the updated kernel and system map
 images. Default is /boot, but you can set it to other values.

 INSTALLKERNEL
 --------------------------------------------------
 Install script called when using "make install".
 The default name is "installkernel".

 The script will be called with the following arguments:
     $1 - kernel version
     $2 - kernel image file
     $3 - kernel map file
     $4 - default install path (use root directory if blank)

 The implementation of "make install" is architecture specific
 and it may differ from the above.

 INSTALLKERNEL is provided to enable the possibility to
 specify a custom installer when cross compiling a kernel.

 MODLIB
 --------------------------------------------------
 Specify where to install modules.
 The default value is:

      $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)

 The value can be overridden in which case the default value is ignored.

 INSTALL_MOD_PATH
 --------------------------------------------------
 INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
 relocations required by build roots.  This is not defined in the
 makefile but the argument can be passed to make if needed.

 INSTALL_MOD_STRIP
 --------------------------------------------------
 INSTALL_MOD_STRIP, if defined, will cause modules to be
 stripped after they are installed.  If INSTALL_MOD_STRIP is '1', then
 the default option --strip-debug will be used.  Otherwise,
 INSTALL_MOD_STRIP value will be used as the options to the strip command.

 INSTALL_FW_PATH
 --------------------------------------------------
 INSTALL_FW_PATH specifies where to install the firmware blobs.
 The default value is:

     $(INSTALL_MOD_PATH)/lib/firmware

 The value can be overridden in which case the default value is ignored.

 INSTALL_HDR_PATH
 --------------------------------------------------
 INSTALL_HDR_PATH specifies where to install user space headers when
 executing "make headers_*".
 The default value is:

     $(objtree)/usr

 $(objtree) is the directory where output files are saved.
 The output directory is often set using "O=..." on the commandline.

 The value can be overridden in which case the default value is ignored.

 KBUILD_MODPOST_WARN
 --------------------------------------------------
 KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined
 symbols in the final module linking stage. It changes such errors
 into warnings.

 KBUILD_MODPOST_NOFINAL
 --------------------------------------------------
 KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
 This is solely useful to speed up test compiles.

 KBUILD_EXTRA_SYMBOLS
 --------------------------------------------------
 For modules that use symbols from other modules.
 See more details in modules.txt.

 ALLSOURCE_ARCHS
 --------------------------------------------------
 For tags/TAGS/cscope targets, you can specify more than one arch
 to be included in the databases, separated by blank space. E.g.:

     $ make ALLSOURCE_ARCHS="x86 mips arm" tags

 To get all available archs you can also specify all. E.g.:

     $ make ALLSOURCE_ARCHS=all tags

 KBUILD_ENABLE_EXTRA_GCC_CHECKS
 --------------------------------------------------
 If enabled over the make command line with "W=1", it turns on additional
 gcc -W... options for more extensive build-time checking.

 KBUILD_BUILD_TIMESTAMP
 --------------------------------------------------
 Setting this to a date string overrides the timestamp used in the
 UTS_VERSION definition (uname -v in the running kernel). The default value
 is the output of the date command at one point during build.

 KBUILD_BUILD_USER, KBUILD_BUILD_HOST
 --------------------------------------------------
 These two variables allow to override the user@host string displayed during
 boot and in /proc/version. The default value is the output of the commands
 whoami and host, respectively.
	Output files

	modules.order
	--------------------------------------------------
	This file records the order in which modules appear in Makefiles. This
	is used by modprobe to deterministically resolve aliases that match
	multiple modules.

	modules.builtin
	--------------------------------------------------
	This file lists all modules that are built into the kernel. This is used
	by modprobe to not fail when trying to load something builtin.


	Environment variables

	KCPPFLAGS
	--------------------------------------------------
	Additional options to pass when preprocessing. The preprocessing options
	will be used in all cases where kbuild does preprocessing including
	building C files and assembler files.

	KAFLAGS
	--------------------------------------------------
	Additional options to the assembler (for built-in and modules).

	AFLAGS_MODULE
	--------------------------------------------------
	Addtional module specific options to use for $(AS).

	AFLAGS_KERNEL
	--------------------------------------------------
	Addtional options for $(AS) when used for assembler
	code for code that is compiled as built-in.

	KCFLAGS
	--------------------------------------------------
	Additional options to the C compiler (for built-in and modules).

	CFLAGS_KERNEL
	--------------------------------------------------
	Addtional options for $(CC) when used to compile
	code that is compiled as built-in.

	CFLAGS_MODULE
	--------------------------------------------------
	Addtional module specific options to use for $(CC).

	LDFLAGS_MODULE
	--------------------------------------------------
	Additional options used for $(LD) when linking modules.

	KBUILD_VERBOSE
	--------------------------------------------------
	Set the kbuild verbosity. Can be assigned same values as "V=...".
	See make help for the full list.
	Setting "V=..." takes precedence over KBUILD_VERBOSE.

	KBUILD_EXTMOD
	--------------------------------------------------
	Set the directory to look for the kernel source when building external
	modules.
	The directory can be specified in several ways:
	1) Use "M=..." on the command line
	2) Environment variable KBUILD_EXTMOD
	3) Environment variable SUBDIRS
	The possibilities are listed in the order they take precedence.
	Using "M=..." will always override the others.

	KBUILD_OUTPUT
	--------------------------------------------------
	Specify the output directory when building the kernel.
	The output directory can also be specified using "O=...".
	Setting "O=..." takes precedence over KBUILD_OUTPUT.

	KBUILD_DEBARCH
	--------------------------------------------------
	For the deb-pkg target, allows overriding the normal heuristics deployed by
	deb-pkg. Normally deb-pkg attempts to guess the right architecture based on
	the UTS_MACHINE variable, and on some architectures also the kernel config.
	The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian
	architecture.

	ARCH
	--------------------------------------------------
	Set ARCH to the architecture to be built.
	In most cases the name of the architecture is the same as the
	directory name found in the arch/ directory.
	But some architectures such as x86 and sparc have aliases.
	x86: i386 for 32 bit, x86_64 for 64 bit
	sparc: sparc for 32 bit, sparc64 for 64 bit

	CROSS_COMPILE
	--------------------------------------------------
	Specify an optional fixed part of the binutils filename.
	CROSS_COMPILE can be a part of the filename or the full path.

	CROSS_COMPILE is also used for ccache in some setups.

	CF
	--------------------------------------------------
	Additional options for sparse.
	CF is often used on the command-line like this:

	make CF=-Wbitwise C=2

	INSTALL_PATH
	--------------------------------------------------
	INSTALL_PATH specifies where to place the updated kernel and system map
	images. Default is /boot, but you can set it to other values.

	INSTALLKERNEL
	--------------------------------------------------
	Install script called when using "make install".
	The default name is "installkernel".

	The script will be called with the following arguments:
	$1 - kernel version
	$2 - kernel image file
	$3 - kernel map file
	$4 - default install path (use root directory if blank)

	The implementation of "make install" is architecture specific
	and it may differ from the above.

	INSTALLKERNEL is provided to enable the possibility to
	specify a custom installer when cross compiling a kernel.

	MODLIB
	--------------------------------------------------
	Specify where to install modules.
	The default value is:

	$(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)

	The value can be overridden in which case the default value is ignored.

	INSTALL_MOD_PATH
	--------------------------------------------------
	INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
	relocations required by build roots. This is not defined in the
	makefile but the argument can be passed to make if needed.

	INSTALL_MOD_STRIP
	--------------------------------------------------
	INSTALL_MOD_STRIP, if defined, will cause modules to be
	stripped after they are installed. If INSTALL_MOD_STRIP is '1', then
	the default option --strip-debug will be used. Otherwise,
	INSTALL_MOD_STRIP value will be used as the options to the strip command.

	INSTALL_FW_PATH
	--------------------------------------------------
	INSTALL_FW_PATH specifies where to install the firmware blobs.
	The default value is:

	$(INSTALL_MOD_PATH)/lib/firmware

	The value can be overridden in which case the default value is ignored.

	INSTALL_HDR_PATH
	--------------------------------------------------
	INSTALL_HDR_PATH specifies where to install user space headers when
	executing "make headers_*".
	The default value is:

	$(objtree)/usr

	$(objtree) is the directory where output files are saved.
	The output directory is often set using "O=..." on the commandline.

	The value can be overridden in which case the default value is ignored.

	KBUILD_MODPOST_WARN
	--------------------------------------------------
	KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined
	symbols in the final module linking stage. It changes such errors
	into warnings.

	KBUILD_MODPOST_NOFINAL
	--------------------------------------------------
	KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
	This is solely useful to speed up test compiles.

	KBUILD_EXTRA_SYMBOLS
	--------------------------------------------------
	For modules that use symbols from other modules.
	See more details in modules.txt.

	ALLSOURCE_ARCHS
	--------------------------------------------------
	For tags/TAGS/cscope targets, you can specify more than one arch
	to be included in the databases, separated by blank space. E.g.:

	$ make ALLSOURCE_ARCHS="x86 mips arm" tags

	To get all available archs you can also specify all. E.g.:

	$ make ALLSOURCE_ARCHS=all tags

	KBUILD_ENABLE_EXTRA_GCC_CHECKS
	--------------------------------------------------
	If enabled over the make command line with "W=1", it turns on additional
	gcc -W... options for more extensive build-time checking.

	KBUILD_BUILD_TIMESTAMP
	--------------------------------------------------
	Setting this to a date string overrides the timestamp used in the
	UTS_VERSION definition (uname -v in the running kernel). The default value
	is the output of the date command at one point during build.

	KBUILD_BUILD_USER, KBUILD_BUILD_HOST
	--------------------------------------------------
	These two variables allow to override the user@host string displayed during
	boot and in /proc/version. The default value is the output of the commands
	whoami and host, respectively.