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-rw-r--r--Documentation/kbuild/00-INDEX12
-rw-r--r--Documentation/kbuild/kbuild.txt235
-rw-r--r--Documentation/kbuild/kconfig-language.txt413
-rw-r--r--Documentation/kbuild/kconfig.txt191
-rw-r--r--Documentation/kbuild/makefiles.txt1432
-rw-r--r--Documentation/kbuild/modules.txt541
6 files changed, 0 insertions, 2824 deletions
diff --git a/Documentation/kbuild/00-INDEX b/Documentation/kbuild/00-INDEX
deleted file mode 100644
index e8d2b6d83a3..00000000000
--- a/Documentation/kbuild/00-INDEX
+++ /dev/null
@@ -1,12 +0,0 @@
-00-INDEX
- - this file: info on the kernel build process
-kbuild.txt
- - developer information on kbuild
-kconfig.txt
- - usage help for make *config
-kconfig-language.txt
- - specification of Config Language, the language in Kconfig files
-makefiles.txt
- - developer information for linux kernel makefiles
-modules.txt
- - how to build modules and to install them
diff --git a/Documentation/kbuild/kbuild.txt b/Documentation/kbuild/kbuild.txt
deleted file mode 100644
index 6466704d47b..00000000000
--- a/Documentation/kbuild/kbuild.txt
+++ /dev/null
@@ -1,235 +0,0 @@
-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
---------------------------------------------------
-Additional module specific options to use for $(AS).
-
-AFLAGS_KERNEL
---------------------------------------------------
-Additional 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
---------------------------------------------------
-Additional options for $(CC) when used to compile
-code that is compiled as built-in.
-
-CFLAGS_MODULE
---------------------------------------------------
-Additional module specific options to use for $(CC).
-
-LDFLAGS_MODULE
---------------------------------------------------
-Additional options used for $(LD) when linking modules.
-
-LDFLAGS_vmlinux
---------------------------------------------------
-Additional options passed to final link of vmlinux.
-
-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 value has to
-be a string that can be passed to date -d. 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.
-
-KBUILD_LDS
---------------------------------------------------
-The linker script with full path. Assigned by the top-level Makefile.
-
-KBUILD_VMLINUX_INIT
---------------------------------------------------
-All object files for the init (first) part of vmlinux.
-Files specified with KBUILD_VMLINUX_INIT are linked first.
-
-KBUILD_VMLINUX_MAIN
---------------------------------------------------
-All object files for the main part of vmlinux.
-KBUILD_VMLINUX_INIT and KBUILD_VMLINUX_MAIN together specify
-all the object files used to link vmlinux.
diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
deleted file mode 100644
index a686f9cd69c..00000000000
--- a/Documentation/kbuild/kconfig-language.txt
+++ /dev/null
@@ -1,413 +0,0 @@
-Introduction
-------------
-
-The configuration database is a collection of configuration options
-organized in a tree structure:
-
- +- Code maturity level options
- | +- Prompt for development and/or incomplete code/drivers
- +- General setup
- | +- Networking support
- | +- System V IPC
- | +- BSD Process Accounting
- | +- Sysctl support
- +- Loadable module support
- | +- Enable loadable module support
- | +- Set version information on all module symbols
- | +- Kernel module loader
- +- ...
-
-Every entry has its own dependencies. These dependencies are used
-to determine the visibility of an entry. Any child entry is only
-visible if its parent entry is also visible.
-
-Menu entries
-------------
-
-Most entries define a config option; all other entries help to organize
-them. A single configuration option is defined like this:
-
-config MODVERSIONS
- bool "Set version information on all module symbols"
- depends on MODULES
- help
- Usually, modules have to be recompiled whenever you switch to a new
- kernel. ...
-
-Every line starts with a key word and can be followed by multiple
-arguments. "config" starts a new config entry. The following lines
-define attributes for this config option. Attributes can be the type of
-the config option, input prompt, dependencies, help text and default
-values. A config option can be defined multiple times with the same
-name, but every definition can have only a single input prompt and the
-type must not conflict.
-
-Menu attributes
----------------
-
-A menu entry can have a number of attributes. Not all of them are
-applicable everywhere (see syntax).
-
-- type definition: "bool"/"tristate"/"string"/"hex"/"int"
- Every config option must have a type. There are only two basic types:
- tristate and string; the other types are based on these two. The type
- definition optionally accepts an input prompt, so these two examples
- are equivalent:
-
- bool "Networking support"
- and
- bool
- prompt "Networking support"
-
-- input prompt: "prompt" <prompt> ["if" <expr>]
- Every menu entry can have at most one prompt, which is used to display
- to the user. Optionally dependencies only for this prompt can be added
- with "if".
-
-- default value: "default" <expr> ["if" <expr>]
- A config option can have any number of default values. If multiple
- default values are visible, only the first defined one is active.
- Default values are not limited to the menu entry where they are
- defined. This means the default can be defined somewhere else or be
- overridden by an earlier definition.
- The default value is only assigned to the config symbol if no other
- value was set by the user (via the input prompt above). If an input
- prompt is visible the default value is presented to the user and can
- be overridden by him.
- Optionally, dependencies only for this default value can be added with
- "if".
-
-- type definition + default value:
- "def_bool"/"def_tristate" <expr> ["if" <expr>]
- This is a shorthand notation for a type definition plus a value.
- Optionally dependencies for this default value can be added with "if".
-
-- dependencies: "depends on" <expr>
- This defines a dependency for this menu entry. If multiple
- dependencies are defined, they are connected with '&&'. Dependencies
- are applied to all other options within this menu entry (which also
- accept an "if" expression), so these two examples are equivalent:
-
- bool "foo" if BAR
- default y if BAR
- and
- depends on BAR
- bool "foo"
- default y
-
-- reverse dependencies: "select" <symbol> ["if" <expr>]
- While normal dependencies reduce the upper limit of a symbol (see
- below), reverse dependencies can be used to force a lower limit of
- another symbol. The value of the current menu symbol is used as the
- minimal value <symbol> can be set to. If <symbol> is selected multiple
- times, the limit is set to the largest selection.
- Reverse dependencies can only be used with boolean or tristate
- symbols.
- Note:
- select should be used with care. select will force
- a symbol to a value without visiting the dependencies.
- By abusing select you are able to select a symbol FOO even
- if FOO depends on BAR that is not set.
- In general use select only for non-visible symbols
- (no prompts anywhere) and for symbols with no dependencies.
- That will limit the usefulness but on the other hand avoid
- the illegal configurations all over.
-
-- limiting menu display: "visible if" <expr>
- This attribute is only applicable to menu blocks, if the condition is
- false, the menu block is not displayed to the user (the symbols
- contained there can still be selected by other symbols, though). It is
- similar to a conditional "prompt" attribute for individual menu
- entries. Default value of "visible" is true.
-
-- numerical ranges: "range" <symbol> <symbol> ["if" <expr>]
- This allows to limit the range of possible input values for int
- and hex symbols. The user can only input a value which is larger than
- or equal to the first symbol and smaller than or equal to the second
- symbol.
-
-- help text: "help" or "---help---"
- This defines a help text. The end of the help text is determined by
- the indentation level, this means it ends at the first line which has
- a smaller indentation than the first line of the help text.
- "---help---" and "help" do not differ in behaviour, "---help---" is
- used to help visually separate configuration logic from help within
- the file as an aid to developers.
-
-- misc options: "option" <symbol>[=<value>]
- Various less common options can be defined via this option syntax,
- which can modify the behaviour of the menu entry and its config
- symbol. These options are currently possible:
-
- - "defconfig_list"
- This declares a list of default entries which can be used when
- looking for the default configuration (which is used when the main
- .config doesn't exists yet.)
-
- - "modules"
- This declares the symbol to be used as the MODULES symbol, which
- enables the third modular state for all config symbols.
-
- - "env"=<value>
- This imports the environment variable into Kconfig. It behaves like
- a default, except that the value comes from the environment, this
- also means that the behaviour when mixing it with normal defaults is
- undefined at this point. The symbol is currently not exported back
- to the build environment (if this is desired, it can be done via
- another symbol).
-
-Menu dependencies
------------------
-
-Dependencies define the visibility of a menu entry and can also reduce
-the input range of tristate symbols. The tristate logic used in the
-expressions uses one more state than normal boolean logic to express the
-module state. Dependency expressions have the following syntax:
-
-<expr> ::= <symbol> (1)
- <symbol> '=' <symbol> (2)
- <symbol> '!=' <symbol> (3)
- '(' <expr> ')' (4)
- '!' <expr> (5)
- <expr> '&&' <expr> (6)
- <expr> '||' <expr> (7)
-
-Expressions are listed in decreasing order of precedence.
-
-(1) Convert the symbol into an expression. Boolean and tristate symbols
- are simply converted into the respective expression values. All
- other symbol types result in 'n'.
-(2) If the values of both symbols are equal, it returns 'y',
- otherwise 'n'.
-(3) If the values of both symbols are equal, it returns 'n',
- otherwise 'y'.
-(4) Returns the value of the expression. Used to override precedence.
-(5) Returns the result of (2-/expr/).
-(6) Returns the result of min(/expr/, /expr/).
-(7) Returns the result of max(/expr/, /expr/).
-
-An expression can have a value of 'n', 'm' or 'y' (or 0, 1, 2
-respectively for calculations). A menu entry becomes visible when its
-expression evaluates to 'm' or 'y'.
-
-There are two types of symbols: constant and non-constant symbols.
-Non-constant symbols are the most common ones and are defined with the
-'config' statement. Non-constant symbols consist entirely of alphanumeric
-characters or underscores.
-Constant symbols are only part of expressions. Constant symbols are
-always surrounded by single or double quotes. Within the quote, any
-other character is allowed and the quotes can be escaped using '\'.
-
-Menu structure
---------------
-
-The position of a menu entry in the tree is determined in two ways. First
-it can be specified explicitly:
-
-menu "Network device support"
- depends on NET
-
-config NETDEVICES
- ...
-
-endmenu
-
-All entries within the "menu" ... "endmenu" block become a submenu of
-"Network device support". All subentries inherit the dependencies from
-the menu entry, e.g. this means the dependency "NET" is added to the
-dependency list of the config option NETDEVICES.
-
-The other way to generate the menu structure is done by analyzing the
-dependencies. If a menu entry somehow depends on the previous entry, it
-can be made a submenu of it. First, the previous (parent) symbol must
-be part of the dependency list and then one of these two conditions
-must be true:
-- the child entry must become invisible, if the parent is set to 'n'
-- the child entry must only be visible, if the parent is visible
-
-config MODULES
- bool "Enable loadable module support"
-
-config MODVERSIONS
- bool "Set version information on all module symbols"
- depends on MODULES
-
-comment "module support disabled"
- depends on !MODULES
-
-MODVERSIONS directly depends on MODULES, this means it's only visible if
-MODULES is different from 'n'. The comment on the other hand is always
-visible when MODULES is visible (the (empty) dependency of MODULES is
-also part of the comment dependencies).
-
-
-Kconfig syntax
---------------
-
-The configuration file describes a series of menu entries, where every
-line starts with a keyword (except help texts). The following keywords
-end a menu entry:
-- config
-- menuconfig
-- choice/endchoice
-- comment
-- menu/endmenu
-- if/endif
-- source
-The first five also start the definition of a menu entry.
-
-config:
-
- "config" <symbol>
- <config options>
-
-This defines a config symbol <symbol> and accepts any of above
-attributes as options.
-
-menuconfig:
- "menuconfig" <symbol>
- <config options>
-
-This is similar to the simple config entry above, but it also gives a
-hint to front ends, that all suboptions should be displayed as a
-separate list of options.
-
-choices:
-
- "choice" [symbol]
- <choice options>
- <choice block>
- "endchoice"
-
-This defines a choice group and accepts any of the above attributes as
-options. A choice can only be of type bool or tristate, while a boolean
-choice only allows a single config entry to be selected, a tristate
-choice also allows any number of config entries to be set to 'm'. This
-can be used if multiple drivers for a single hardware exists and only a
-single driver can be compiled/loaded into the kernel, but all drivers
-can be compiled as modules.
-A choice accepts another option "optional", which allows to set the
-choice to 'n' and no entry needs to be selected.
-If no [symbol] is associated with a choice, then you can not have multiple
-definitions of that choice. If a [symbol] is associated to the choice,
-then you may define the same choice (ie. with the same entries) in another
-place.
-
-comment:
-
- "comment" <prompt>
- <comment options>
-
-This defines a comment which is displayed to the user during the
-configuration process and is also echoed to the output files. The only
-possible options are dependencies.
-
-menu:
-
- "menu" <prompt>
- <menu options>
- <menu block>
- "endmenu"
-
-This defines a menu block, see "Menu structure" above for more
-information. The only possible options are dependencies and "visible"
-attributes.
-
-if:
-
- "if" <expr>
- <if block>
- "endif"
-
-This defines an if block. The dependency expression <expr> is appended
-to all enclosed menu entries.
-
-source:
-
- "source" <prompt>
-
-This reads the specified configuration file. This file is always parsed.
-
-mainmenu:
-
- "mainmenu" <prompt>
-
-This sets the config program's title bar if the config program chooses
-to use it. It should be placed at the top of the configuration, before any
-other statement.
-
-
-Kconfig hints
--------------
-This is a collection of Kconfig tips, most of which aren't obvious at
-first glance and most of which have become idioms in several Kconfig
-files.
-
-Adding common features and make the usage configurable
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-It is a common idiom to implement a feature/functionality that are
-relevant for some architectures but not all.
-The recommended way to do so is to use a config variable named HAVE_*
-that is defined in a common Kconfig file and selected by the relevant
-architectures.
-An example is the generic IOMAP functionality.
-
-We would in lib/Kconfig see:
-
-# Generic IOMAP is used to ...
-config HAVE_GENERIC_IOMAP
-
-config GENERIC_IOMAP
- depends on HAVE_GENERIC_IOMAP && FOO
-
-And in lib/Makefile we would see:
-obj-$(CONFIG_GENERIC_IOMAP) += iomap.o
-
-For each architecture using the generic IOMAP functionality we would see:
-
-config X86
- select ...
- select HAVE_GENERIC_IOMAP
- select ...
-
-Note: we use the existing config option and avoid creating a new
-config variable to select HAVE_GENERIC_IOMAP.
-
-Note: the use of the internal config variable HAVE_GENERIC_IOMAP, it is
-introduced to overcome the limitation of select which will force a
-config option to 'y' no matter the dependencies.
-The dependencies are moved to the symbol GENERIC_IOMAP and we avoid the
-situation where select forces a symbol equals to 'y'.
-
-Build as module only
-~~~~~~~~~~~~~~~~~~~~
-To restrict a component build to module-only, qualify its config symbol
-with "depends on m". E.g.:
-
-config FOO
- depends on BAR && m
-
-limits FOO to module (=m) or disabled (=n).
-
-Kconfig symbol existence
-~~~~~~~~~~~~~~~~~~~~~~~~
-The following two methods produce the same kconfig symbol dependencies
-but differ greatly in kconfig symbol existence (production) in the
-generated config file.
-
-case 1:
-
-config FOO
- tristate "about foo"
- depends on BAR
-
-vs. case 2:
-
-if BAR
-config FOO
- tristate "about foo"
-endif
-
-In case 1, the symbol FOO will always exist in the config file (given
-no other dependencies). In case 2, the symbol FOO will only exist in
-the config file if BAR is enabled.
diff --git a/Documentation/kbuild/kconfig.txt b/Documentation/kbuild/kconfig.txt
deleted file mode 100644
index a09f1a6a830..00000000000
--- a/Documentation/kbuild/kconfig.txt
+++ /dev/null
@@ -1,191 +0,0 @@
-This file contains some assistance for using "make *config".
-
-Use "make help" to list all of the possible configuration targets.
-
-The xconfig ('qconf') and menuconfig ('mconf') programs also
-have embedded help text. Be sure to check it for navigation,
-search, and other general help text.
-
-======================================================================
-General
---------------------------------------------------
-
-New kernel releases often introduce new config symbols. Often more
-important, new kernel releases may rename config symbols. When
-this happens, using a previously working .config file and running
-"make oldconfig" won't necessarily produce a working new kernel
-for you, so you may find that you need to see what NEW kernel
-symbols have been introduced.
-
-To see a list of new config symbols when using "make oldconfig", use
-
- cp user/some/old.config .config
- yes "" | make oldconfig >conf.new
-
-and the config program will list as (NEW) any new symbols that have
-unknown values. Of course, the .config file is also updated with
-new (default) values, so you can use:
-
- grep "(NEW)" conf.new
-
-to see the new config symbols or you can use diffconfig to see the
-differences between the previous and new .config files:
-
- scripts/diffconfig .config.old .config | less
-
-______________________________________________________________________
-Environment variables for '*config'
-
-KCONFIG_CONFIG
---------------------------------------------------
-This environment variable can be used to specify a default kernel config
-file name to override the default name of ".config".
-
-KCONFIG_OVERWRITECONFIG
---------------------------------------------------
-If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
-break symlinks when .config is a symlink to somewhere else.
-
-______________________________________________________________________
-Environment variables for '{allyes/allmod/allno/rand}config'
-
-KCONFIG_ALLCONFIG
---------------------------------------------------
-(partially based on lkml email from/by Rob Landley, re: miniconfig)
---------------------------------------------------
-The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also
-use the environment variable KCONFIG_ALLCONFIG as a flag or a filename
-that contains config symbols that the user requires to be set to a
-specific value. If KCONFIG_ALLCONFIG is used without a filename where
-KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", "make *config"
-checks for a file named "all{yes/mod/no/def/random}.config"
-(corresponding to the *config command that was used) for symbol values
-that are to be forced. If this file is not found, it checks for a
-file named "all.config" to contain forced values.
-
-This enables you to create "miniature" config (miniconfig) or custom
-config files containing just the config symbols that you are interested
-in. Then the kernel config system generates the full .config file,
-including symbols of your miniconfig file.
-
-This 'KCONFIG_ALLCONFIG' file is a config file which contains
-(usually a subset of all) preset config symbols. These variable
-settings are still subject to normal dependency checks.
-
-Examples:
- KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
-or
- KCONFIG_ALLCONFIG=mini.config make allnoconfig
-or
- make KCONFIG_ALLCONFIG=mini.config allnoconfig
-
-These examples will disable most options (allnoconfig) but enable or
-disable the options that are explicitly listed in the specified
-mini-config files.
-
-______________________________________________________________________
-Environment variables for 'silentoldconfig'
-
-KCONFIG_NOSILENTUPDATE
---------------------------------------------------
-If this variable has a non-blank value, it prevents silent kernel
-config updates (requires explicit updates).
-
-KCONFIG_AUTOCONFIG
---------------------------------------------------
-This environment variable can be set to specify the path & name of the
-"auto.conf" file. Its default value is "include/config/auto.conf".
-
-KCONFIG_TRISTATE
---------------------------------------------------
-This environment variable can be set to specify the path & name of the
-"tristate.conf" file. Its default value is "include/config/tristate.conf".
-
-KCONFIG_AUTOHEADER
---------------------------------------------------
-This environment variable can be set to specify the path & name of the
-"autoconf.h" (header) file.
-Its default value is "include/generated/autoconf.h".
-
-
-======================================================================
-menuconfig
---------------------------------------------------
-
-SEARCHING for CONFIG symbols
-
-Searching in menuconfig:
-
- The Search function searches for kernel configuration symbol
- names, so you have to know something close to what you are
- looking for.
-
- Example:
- /hotplug
- This lists all config symbols that contain "hotplug",
- e.g., HOTPLUG, HOTPLUG_CPU, MEMORY_HOTPLUG.
-
- For search help, enter / followed TAB-TAB-TAB (to highlight
- <Help>) and Enter. This will tell you that you can also use
- regular expressions (regexes) in the search string, so if you
- are not interested in MEMORY_HOTPLUG, you could try
-
- /^hotplug
-
-______________________________________________________________________
-User interface options for 'menuconfig'
-
-MENUCONFIG_COLOR
---------------------------------------------------
-It is possible to select different color themes using the variable
-MENUCONFIG_COLOR. To select a theme use:
-
- make MENUCONFIG_COLOR=<theme> menuconfig
-
-Available themes are:
- mono => selects colors suitable for monochrome displays
- blackbg => selects a color scheme with black background
- classic => theme with blue background. The classic look
- bluetitle => a LCD friendly version of classic. (default)
-
-MENUCONFIG_MODE
---------------------------------------------------
-This mode shows all sub-menus in one large tree.
-
-Example:
- make MENUCONFIG_MODE=single_menu menuconfig
-
-
-======================================================================
-xconfig
---------------------------------------------------
-
-Searching in xconfig:
-
- The Search function searches for kernel configuration symbol
- names, so you have to know something close to what you are
- looking for.
-
- Example:
- Ctrl-F hotplug
- or
- Menu: File, Search, hotplug
-
- lists all config symbol entries that contain "hotplug" in
- the symbol name. In this Search dialog, you may change the
- config setting for any of the entries that are not grayed out.
- You can also enter a different search string without having
- to return to the main menu.
-
-
-======================================================================
-gconfig
---------------------------------------------------
-
-Searching in gconfig:
-
- None (gconfig isn't maintained as well as xconfig or menuconfig);
- however, gconfig does have a few more viewing choices than
- xconfig does.
-
-###
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
deleted file mode 100644
index ab0a984530d..00000000000
--- a/Documentation/kbuild/makefiles.txt
+++ /dev/null
@@ -1,1432 +0,0 @@
-Linux Kernel Makefiles
-
-This document describes the Linux kernel Makefiles.
-
-=== Table of Contents
-
- === 1 Overview
- === 2 Who does what
- === 3 The kbuild files
- --- 3.1 Goal definitions
- --- 3.2 Built-in object goals - obj-y
- --- 3.3 Loadable module goals - obj-m
- --- 3.4 Objects which export symbols
- --- 3.5 Library file goals - lib-y
- --- 3.6 Descending down in directories
- --- 3.7 Compilation flags
- --- 3.8 Command line dependency
- --- 3.9 Dependency tracking
- --- 3.10 Special Rules
- --- 3.11 $(CC) support functions
- --- 3.12 $(LD) support functions
-
- === 4 Host Program support
- --- 4.1 Simple Host Program
- --- 4.2 Composite Host Programs
- --- 4.3 Defining shared libraries
- --- 4.4 Using C++ for host programs
- --- 4.5 Controlling compiler options for host programs
- --- 4.6 When host programs are actually built
- --- 4.7 Using hostprogs-$(CONFIG_FOO)
-
- === 5 Kbuild clean infrastructure
-
- === 6 Architecture Makefiles
- --- 6.1 Set variables to tweak the build to the architecture
- --- 6.2 Add prerequisites to archheaders:
- --- 6.3 Add prerequisites to archprepare:
- --- 6.4 List directories to visit when descending
- --- 6.5 Architecture-specific boot images
- --- 6.6 Building non-kbuild targets
- --- 6.7 Commands useful for building a boot image
- --- 6.8 Custom kbuild commands
- --- 6.9 Preprocessing linker scripts
- --- 6.10 Generic header files
-
- === 7 Kbuild syntax for exported headers
- --- 7.1 header-y
- --- 7.2 objhdr-y
- --- 7.3 destination-y
- --- 7.4 generic-y
-
- === 8 Kbuild Variables
- === 9 Makefile language
- === 10 Credits
- === 11 TODO
-
-=== 1 Overview
-
-The Makefiles have five parts:
-
- Makefile the top Makefile.
- .config the kernel configuration file.
- arch/$(ARCH)/Makefile the arch Makefile.
- scripts/Makefile.* common rules etc. for all kbuild Makefiles.
- kbuild Makefiles there are about 500 of these.
-
-The top Makefile reads the .config file, which comes from the kernel
-configuration process.
-
-The top Makefile is responsible for building two major products: vmlinux
-(the resident kernel image) and modules (any module files).
-It builds these goals by recursively descending into the subdirectories of
-the kernel source tree.
-The list of subdirectories which are visited depends upon the kernel
-configuration. The top Makefile textually includes an arch Makefile
-with the name arch/$(ARCH)/Makefile. The arch Makefile supplies
-architecture-specific information to the top Makefile.
-
-Each subdirectory has a kbuild Makefile which carries out the commands
-passed down from above. The kbuild Makefile uses information from the
-.config file to construct various file lists used by kbuild to build
-any built-in or modular targets.
-
-scripts/Makefile.* contains all the definitions/rules etc. that
-are used to build the kernel based on the kbuild makefiles.
-
-
-=== 2 Who does what
-
-People have four different relationships with the kernel Makefiles.
-
-*Users* are people who build kernels. These people type commands such as
-"make menuconfig" or "make". They usually do not read or edit
-any kernel Makefiles (or any other source files).
-
-*Normal developers* are people who work on features such as device
-drivers, file systems, and network protocols. These people need to
-maintain the kbuild Makefiles for the subsystem they are
-working on. In order to do this effectively, they need some overall
-knowledge about the kernel Makefiles, plus detailed knowledge about the
-public interface for kbuild.
-
-*Arch developers* are people who work on an entire architecture, such
-as sparc or ia64. Arch developers need to know about the arch Makefile
-as well as kbuild Makefiles.
-
-*Kbuild developers* are people who work on the kernel build system itself.
-These people need to know about all aspects of the kernel Makefiles.
-
-This document is aimed towards normal developers and arch developers.
-
-
-=== 3 The kbuild files
-
-Most Makefiles within the kernel are kbuild Makefiles that use the
-kbuild infrastructure. This chapter introduces the syntax used in the
-kbuild makefiles.
-The preferred name for the kbuild files are 'Makefile' but 'Kbuild' can
-be used and if both a 'Makefile' and a 'Kbuild' file exists, then the 'Kbuild'
-file will be used.
-
-Section 3.1 "Goal definitions" is a quick intro, further chapters provide
-more details, with real examples.
-
---- 3.1 Goal definitions
-
- Goal definitions are the main part (heart) of the kbuild Makefile.
- These lines define the files to be built, any special compilation
- options, and any subdirectories to be entered recursively.
-
- The most simple kbuild makefile contains one line:
-
- Example:
- obj-y += foo.o
-
- This tells kbuild that there is one object in that directory, named
- foo.o. foo.o will be built from foo.c or foo.S.
-
- If foo.o shall be built as a module, the variable obj-m is used.
- Therefore the following pattern is often used:
-
- Example:
- obj-$(CONFIG_FOO) += foo.o
-
- $(CONFIG_FOO) evaluates to either y (for built-in) or m (for module).
- If CONFIG_FOO is neither y nor m, then the file will not be compiled
- nor linked.
-
---- 3.2 Built-in object goals - obj-y
-
- The kbuild Makefile specifies object files for vmlinux
- in the $(obj-y) lists. These lists depend on the kernel
- configuration.
-
- Kbuild compiles all the $(obj-y) files. It then calls
- "$(LD) -r" to merge these files into one built-in.o file.
- built-in.o is later linked into vmlinux by the parent Makefile.
-
- The order of files in $(obj-y) is significant. Duplicates in
- the lists are allowed: the first instance will be linked into
- built-in.o and succeeding instances will be ignored.
-
- Link order is significant, because certain functions
- (module_init() / __initcall) will be called during boot in the
- order they appear. So keep in mind that changing the link
- order may e.g. change the order in which your SCSI
- controllers are detected, and thus your disks are renumbered.
-
- Example:
- #drivers/isdn/i4l/Makefile
- # Makefile for the kernel ISDN subsystem and device drivers.
- # Each configuration option enables a list of files.
- obj-$(CONFIG_ISDN_I4L) += isdn.o
- obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
-
---- 3.3 Loadable module goals - obj-m
-
- $(obj-m) specify object files which are built as loadable
- kernel modules.
-
- A module may be built from one source file or several source
- files. In the case of one source file, the kbuild makefile
- simply adds the file to $(obj-m).
-
- Example:
- #drivers/isdn/i4l/Makefile
- obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
-
- Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm'
-
- If a kernel module is built from several source files, you specify
- that you want to build a module in the same way as above; however,
- kbuild needs to know which object files you want to build your
- module from, so you have to tell it by setting a $(<module_name>-y)
- variable.
-
- Example:
- #drivers/isdn/i4l/Makefile
- obj-$(CONFIG_ISDN_I4L) += isdn.o
- isdn-y := isdn_net_lib.o isdn_v110.o isdn_common.o
-
- In this example, the module name will be isdn.o. Kbuild will
- compile the objects listed in $(isdn-y) and then run
- "$(LD) -r" on the list of these files to generate isdn.o.
-
- Due to kbuild recognizing $(<module_name>-y) for composite objects,
- you can use the value of a CONFIG_ symbol to optionally include an
- object file as part of a composite object.
-
- Example:
- #fs/ext2/Makefile
- obj-$(CONFIG_EXT2_FS) += ext2.o
- ext2-y := balloc.o dir.o file.o ialloc.o inode.o ioctl.o \
- namei.o super.o symlink.o
- ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o xattr_user.o \
- xattr_trusted.o
-
- In this example, xattr.o, xattr_user.o and xattr_trusted.o are only
- part of the composite object ext2.o if $(CONFIG_EXT2_FS_XATTR)
- evaluates to 'y'.
-
- Note: Of course, when you are building objects into the kernel,
- the syntax above will also work. So, if you have CONFIG_EXT2_FS=y,
- kbuild will build an ext2.o file for you out of the individual
- parts and then link this into built-in.o, as you would expect.
-
---- 3.4 Objects which export symbols
-
- No special notation is required in the makefiles for
- modules exporting symbols.
-
---- 3.5 Library file goals - lib-y
-
- Objects listed with obj-* are used for modules, or
- combined in a built-in.o for that specific directory.
- There is also the possibility to list objects that will
- be included in a library, lib.a.
- All objects listed with lib-y are combined in a single
- library for that directory.
- Objects that are listed in obj-y and additionally listed in
- lib-y will not be included in the library, since they will
- be accessible anyway.
- For consistency, objects listed in lib-m will be included in lib.a.
-
- Note that the same kbuild makefile may list files to be built-in
- and to be part of a library. Therefore the same directory
- may contain both a built-in.o and a lib.a file.
-
- Example:
- #arch/x86/lib/Makefile
- lib-y := delay.o
-
- This will create a library lib.a based on delay.o. For kbuild to
- actually recognize that there is a lib.a being built, the directory
- shall be listed in libs-y.
- See also "6.4 List directories to visit when descending".
-
- Use of lib-y is normally restricted to lib/ and arch/*/lib.
-
---- 3.6 Descending down in directories
-
- A Makefile is only responsible for building objects in its own
- directory. Files in subdirectories should be taken care of by
- Makefiles in these subdirs. The build system will automatically
- invoke make recursively in subdirectories, provided you let it know of
- them.
-
- To do so, obj-y and obj-m are used.
- ext2 lives in a separate directory, and the Makefile present in fs/
- tells kbuild to descend down using the following assignment.
-
- Example:
- #fs/Makefile
- obj-$(CONFIG_EXT2_FS) += ext2/
-
- If CONFIG_EXT2_FS is set to either 'y' (built-in) or 'm' (modular)
- the corresponding obj- variable will be set, and kbuild will descend
- down in the ext2 directory.
- Kbuild only uses this information to decide that it needs to visit
- the directory, it is the Makefile in the subdirectory that
- specifies what is modules and what is built-in.
-
- It is good practice to use a CONFIG_ variable when assigning directory
- names. This allows kbuild to totally skip the directory if the
- corresponding CONFIG_ option is neither 'y' nor 'm'.
-
---- 3.7 Compilation flags
-
- ccflags-y, asflags-y and ldflags-y
- These three flags apply only to the kbuild makefile in which they
- are assigned. They are used for all the normal cc, as and ld
- invocations happening during a recursive build.
- Note: Flags with the same behaviour were previously named:
- EXTRA_CFLAGS, EXTRA_AFLAGS and EXTRA_LDFLAGS.
- They are still supported but their usage is deprecated.
-
- ccflags-y specifies options for compiling with $(CC).
-
- Example:
- # drivers/acpi/Makefile
- ccflags-y := -Os
- ccflags-$(CONFIG_ACPI_DEBUG) += -DACPI_DEBUG_OUTPUT
-
- This variable is necessary because the top Makefile owns the
- variable $(KBUILD_CFLAGS) and uses it for compilation flags for the
- entire tree.
-
- asflags-y specifies options for assembling with $(AS).
-
- Example:
- #arch/sparc/kernel/Makefile
- asflags-y := -ansi
-
- ldflags-y specifies options for linking with $(LD).
-
- Example:
- #arch/cris/boot/compressed/Makefile
- ldflags-y += -T $(srctree)/$(src)/decompress_$(arch-y).lds
-
- subdir-ccflags-y, subdir-asflags-y
- The two flags listed above are similar to ccflags-y and asflags-y.
- The difference is that the subdir- variants have effect for the kbuild
- file where they are present and all subdirectories.
- Options specified using subdir-* are added to the commandline before
- the options specified using the non-subdir variants.
-
- Example:
- subdir-ccflags-y := -Werror
-
- CFLAGS_$@, AFLAGS_$@
-
- CFLAGS_$@ and AFLAGS_$@ only apply to commands in current
- kbuild makefile.
-
- $(CFLAGS_$@) specifies per-file options for $(CC). The $@
- part has a literal value which specifies the file that it is for.
-
- Example:
- # drivers/scsi/Makefile
- CFLAGS_aha152x.o = -DAHA152X_STAT -DAUTOCONF
- CFLAGS_gdth.o = # -DDEBUG_GDTH=2 -D__SERIAL__ -D__COM2__ \
- -DGDTH_STATISTICS
-
- These two lines specify compilation flags for aha152x.o and gdth.o.
-
- $(AFLAGS_$@) is a similar feature for source files in assembly
- languages.
-
- Example:
- # arch/arm/kernel/Makefile
- AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
- AFLAGS_crunch-bits.o := -Wa,-mcpu=ep9312
- AFLAGS_iwmmxt.o := -Wa,-mcpu=iwmmxt
-
-
---- 3.9 Dependency tracking
-
- Kbuild tracks dependencies on the following:
- 1) All prerequisite files (both *.c and *.h)
- 2) CONFIG_ options used in all prerequisite files
- 3) Command-line used to compile target
-
- Thus, if you change an option to $(CC) all affected files will
- be re-compiled.
-
---- 3.10 Special Rules
-
- Special rules are used when the kbuild infrastructure does
- not provide the required support. A typical example is
- header files generated during the build process.
- Another example are the architecture-specific Makefiles which
- need special rules to prepare boot images etc.
-
- Special rules are written as normal Make rules.
- Kbuild is not executing in the directory where the Makefile is
- located, so all special rules shall provide a relative
- path to prerequisite files and target files.
-
- Two variables are used when defining special rules:
-
- $(src)
- $(src) is a relative path which points to the directory
- where the Makefile is located. Always use $(src) when
- referring to files located in the src tree.
-
- $(obj)
- $(obj) is a relative path which points to the directory
- where the target is saved. Always use $(obj) when
- referring to generated files.
-
- Example:
- #drivers/scsi/Makefile
- $(obj)/53c8xx_d.h: $(src)/53c7,8xx.scr $(src)/script_asm.pl
- $(CPP) -DCHIP=810 - < $< | ... $(src)/script_asm.pl
-
- This is a special rule, following the normal syntax
- required by make.
- The target file depends on two prerequisite files. References
- to the target file are prefixed with $(obj), references
- to prerequisites are referenced with $(src) (because they are not
- generated files).
-
- $(kecho)
- echoing information to user in a rule is often a good practice
- but when execution "make -s" one does not expect to see any output
- except for warnings/errors.
- To support this kbuild define $(kecho) which will echo out the
- text following $(kecho) to stdout except if "make -s" is used.
-
- Example:
- #arch/blackfin/boot/Makefile
- $(obj)/vmImage: $(obj)/vmlinux.gz
- $(call if_changed,uimage)
- @$(kecho) 'Kernel: $@ is ready'
-
-
---- 3.11 $(CC) support functions
-
- The kernel may be built with several different versions of
- $(CC), each supporting a unique set of features and options.
- kbuild provide basic support to check for valid options for $(CC).
- $(CC) is usually the gcc compiler, but other alternatives are
- available.
-
- as-option
- as-option is used to check if $(CC) -- when used to compile
- assembler (*.S) files -- supports the given option. An optional
- second option may be specified if the first option is not supported.
-
- Example:
- #arch/sh/Makefile
- cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),)
-
- In the above example, cflags-y will be assigned the option
- -Wa$(comma)-isa=$(isa-y) if it is supported by $(CC).
- The second argument is optional, and if supplied will be used
- if first argument is not supported.
-
- cc-ldoption
- cc-ldoption is used to check if $(CC) when used to link object files
- supports the given option. An optional second option may be
- specified if first option are not supported.
-
- Example:
- #arch/x86/kernel/Makefile
- vsyscall-flags += $(call cc-ldoption, -Wl$(comma)--hash-style=sysv)
-
- In the above example, vsyscall-flags will be assigned the option
- -Wl$(comma)--hash-style=sysv if it is supported by $(CC).
- The second argument is optional, and if supplied will be used
- if first argument is not supported.
-
- as-instr
- as-instr checks if the assembler reports a specific instruction
- and then outputs either option1 or option2
- C escapes are supported in the test instruction
- Note: as-instr-option uses KBUILD_AFLAGS for $(AS) options
-
- cc-option
- cc-option is used to check if $(CC) supports a given option, and not
- supported to use an optional second option.
-
- Example:
- #arch/x86/Makefile
- cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
-
- In the above example, cflags-y will be assigned the option
- -march=pentium-mmx if supported by $(CC), otherwise -march=i586.
- The second argument to cc-option is optional, and if omitted,
- cflags-y will be assigned no value if first option is not supported.
- Note: cc-option uses KBUILD_CFLAGS for $(CC) options
-
- cc-option-yn
- cc-option-yn is used to check if gcc supports a given option
- and return 'y' if supported, otherwise 'n'.
-
- Example:
- #arch/ppc/Makefile
- biarch := $(call cc-option-yn, -m32)
- aflags-$(biarch) += -a32
- cflags-$(biarch) += -m32
-
- In the above example, $(biarch) is set to y if $(CC) supports the -m32
- option. When $(biarch) equals 'y', the expanded variables $(aflags-y)
- and $(cflags-y) will be assigned the values -a32 and -m32,
- respectively.
- Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options
-
- cc-option-align
- gcc versions >= 3.0 changed the type of options used to specify
- alignment of functions, loops etc. $(cc-option-align), when used
- as prefix to the align options, will select the right prefix:
- gcc < 3.00
- cc-option-align = -malign
- gcc >= 3.00
- cc-option-align = -falign
-
- Example:
- KBUILD_CFLAGS += $(cc-option-align)-functions=4
-
- In the above example, the option -falign-functions=4 is used for
- gcc >= 3.00. For gcc < 3.00, -malign-functions=4 is used.
- Note: cc-option-align uses KBUILD_CFLAGS for $(CC) options
-
- cc-disable-warning
- cc-disable-warning checks if gcc supports a given warning and returns
- the commandline switch to disable it. This special function is needed,
- because gcc 4.4 and later accept any unknown -Wno-* option and only
- warn about it if there is another warning in the source file.
-
- Example:
- KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
-
- In the above example, -Wno-unused-but-set-variable will be added to
- KBUILD_CFLAGS only if gcc really accepts it.
-
- cc-version
- cc-version returns a numerical version of the $(CC) compiler version.
- The format is <major><minor> where both are two digits. So for example
- gcc 3.41 would return 0341.
- cc-version is useful when a specific $(CC) version is faulty in one
- area, for example -mregparm=3 was broken in some gcc versions
- even though the option was accepted by gcc.
-
- Example:
- #arch/x86/Makefile
- cflags-y += $(shell \
- if [ $(call cc-version) -ge 0300 ] ; then \
- echo "-mregparm=3"; fi ;)
-
- In the above example, -mregparm=3 is only used for gcc version greater
- than or equal to gcc 3.0.
-
- cc-ifversion
- cc-ifversion tests the version of $(CC) and equals last argument if
- version expression is true.
-
- Example:
- #fs/reiserfs/Makefile
- ccflags-y := $(call cc-ifversion, -lt, 0402, -O1)
-
- In this example, ccflags-y will be assigned the value -O1 if the
- $(CC) version is less than 4.2.
- cc-ifversion takes all the shell operators:
- -eq, -ne, -lt, -le, -gt, and -ge
- The third parameter may be a text as in this example, but it may also
- be an expanded variable or a macro.
-
- cc-fullversion
- cc-fullversion is useful when the exact version of gcc is needed.
- One typical use-case is when a specific GCC version is broken.
- cc-fullversion points out a more specific version than cc-version does.
-
- Example:
- #arch/powerpc/Makefile
- $(Q)if test "$(call cc-fullversion)" = "040200" ; then \
- echo -n '*** GCC-4.2.0 cannot compile the 64-bit powerpc ' ; \
- false ; \
- fi
-
- In this example for a specific GCC version the build will error out explaining
- to the user why it stops.
-
- cc-cross-prefix
- cc-cross-prefix is used to check if there exists a $(CC) in path with
- one of the listed prefixes. The first prefix where there exist a
- prefix$(CC) in the PATH is returned - and if no prefix$(CC) is found
- then nothing is returned.
- Additional prefixes are separated by a single space in the
- call of cc-cross-prefix.
- This functionality is useful for architecture Makefiles that try
- to set CROSS_COMPILE to well-known values but may have several
- values to select between.
- It is recommended only to try to set CROSS_COMPILE if it is a cross
- build (host arch is different from target arch). And if CROSS_COMPILE
- is already set then leave it with the old value.
-
- Example:
- #arch/m68k/Makefile
- ifneq ($(SUBARCH),$(ARCH))
- ifeq ($(CROSS_COMPILE),)
- CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu-)
- endif
- endif
-
---- 3.12 $(LD) support functions
-
- ld-option
- ld-option is used to check if $(LD) supports the supplied option.
- ld-option takes two options as arguments.
- The second argument is an optional option that can be used if the
- first option is not supported by $(LD).
-
- Example:
- #Makefile
- LDFLAGS_vmlinux += $(call really-ld-option, -X)
-
-
-=== 4 Host Program support
-
-Kbuild supports building executables on the host for use during the
-compilation stage.
-Two steps are required in order to use a host executable.
-
-The first step is to tell kbuild that a host program exists. This is
-done utilising the variable hostprogs-y.
-
-The second step is to add an explicit dependency to the executable.
-This can be done in two ways. Either add the dependency in a rule,
-or utilise the variable $(always).
-Both possibilities are described in the following.
-
---- 4.1 Simple Host Program
-
- In some cases there is a need to compile and run a program on the
- computer where the build is running.
- The following line tells kbuild that the program bin2hex shall be
- built on the build host.
-
- Example:
- hostprogs-y := bin2hex
-
- Kbuild assumes in the above example that bin2hex is made from a single
- c-source file named bin2hex.c located in the same directory as
- the Makefile.
-
---- 4.2 Composite Host Programs
-
- Host programs can be made up based on composite objects.
- The syntax used to define composite objects for host programs is
- similar to the syntax used for kernel objects.
- $(<executable>-objs) lists all objects used to link the final
- executable.
-
- Example:
- #scripts/lxdialog/Makefile
- hostprogs-y := lxdialog
- lxdialog-objs := checklist.o lxdialog.o
-
- Objects with extension .o are compiled from the corresponding .c
- files. In the above example, checklist.c is compiled to checklist.o
- and lxdialog.c is compiled to lxdialog.o.
- Finally, the two .o files are linked to the executable, lxdialog.
- Note: The syntax <executable>-y is not permitted for host-programs.
-
---- 4.3 Defining shared libraries
-
- Objects with extension .so are considered shared libraries, and
- will be compiled as position independent objects.
- Kbuild provides support for shared libraries, but the usage
- shall be restricted.
- In the following example the libkconfig.so shared library is used
- to link the executable conf.
-
- Example:
- #scripts/kconfig/Makefile
- hostprogs-y := conf
- conf-objs := conf.o libkconfig.so
- libkconfig-objs := expr.o type.o
-
- Shared libraries always require a corresponding -objs line, and
- in the example above the shared library libkconfig is composed by
- the two objects expr.o and type.o.
- expr.o and type.o will be built as position independent code and
- linked as a shared library libkconfig.so. C++ is not supported for
- shared libraries.
-
---- 4.4 Using C++ for host programs
-
- kbuild offers support for host programs written in C++. This was
- introduced solely to support kconfig, and is not recommended
- for general use.
-
- Example:
- #scripts/kconfig/Makefile
- hostprogs-y := qconf
- qconf-cxxobjs := qconf.o
-
- In the example above the executable is composed of the C++ file
- qconf.cc - identified by $(qconf-cxxobjs).
-
- If qconf is composed by a mixture of .c and .cc files, then an
- additional line can be used to identify this.
-
- Example:
- #scripts/kconfig/Makefile
- hostprogs-y := qconf
- qconf-cxxobjs := qconf.o
- qconf-objs := check.o
-
---- 4.5 Controlling compiler options for host programs
-
- When compiling host programs, it is possible to set specific flags.
- The programs will always be compiled utilising $(HOSTCC) passed
- the options specified in $(HOSTCFLAGS).
- To set flags that will take effect for all host programs created
- in that Makefile, use the variable HOST_EXTRACFLAGS.
-
- Example:
- #scripts/lxdialog/Makefile
- HOST_EXTRACFLAGS += -I/usr/include/ncurses
-
- To set specific flags for a single file the following construction
- is used:
-
- Example:
- #arch/ppc64/boot/Makefile
- HOSTCFLAGS_piggyback.o := -DKERNELBASE=$(KERNELBASE)
-
- It is also possible to specify additional options to the linker.
-
- Example:
- #scripts/kconfig/Makefile
- HOSTLOADLIBES_qconf := -L$(QTDIR)/lib
-
- When linking qconf, it will be passed the extra option
- "-L$(QTDIR)/lib".
-
---- 4.6 When host programs are actually built
-
- Kbuild will only build host-programs when they are referenced
- as a prerequisite.
- This is possible in two ways:
-
- (1) List the prerequisite explicitly in a special rule.
-
- Example:
- #drivers/pci/Makefile
- hostprogs-y := gen-devlist
- $(obj)/devlist.h: $(src)/pci.ids $(obj)/gen-devlist
- ( cd $(obj); ./gen-devlist ) < $<
-
- The target $(obj)/devlist.h will not be built before
- $(obj)/gen-devlist is updated. Note that references to
- the host programs in special rules must be prefixed with $(obj).
-
- (2) Use $(always)
- When there is no suitable special rule, and the host program
- shall be built when a makefile is entered, the $(always)
- variable shall be used.
-
- Example:
- #scripts/lxdialog/Makefile
- hostprogs-y := lxdialog
- always := $(hostprogs-y)
-
- This will tell kbuild to build lxdialog even if not referenced in
- any rule.
-
---- 4.7 Using hostprogs-$(CONFIG_FOO)
-
- A typical pattern in a Kbuild file looks like this:
-
- Example:
- #scripts/Makefile
- hostprogs-$(CONFIG_KALLSYMS) += kallsyms
-
- Kbuild knows about both 'y' for built-in and 'm' for module.
- So if a config symbol evaluate to 'm', kbuild will still build
- the binary. In other words, Kbuild handles hostprogs-m exactly
- like hostprogs-y. But only hostprogs-y is recommended to be used
- when no CONFIG symbols are involved.
-
-=== 5 Kbuild clean infrastructure
-
-"make clean" deletes most generated files in the obj tree where the kernel
-is compiled. This includes generated files such as host programs.
-Kbuild knows targets listed in $(hostprogs-y), $(hostprogs-m), $(always),
-$(extra-y) and $(targets). They are all deleted during "make clean".
-Files matching the patterns "*.[oas]", "*.ko", plus some additional files
-generated by kbuild are deleted all over the kernel src tree when
-"make clean" is executed.
-
-Additional files can be specified in kbuild makefiles by use of $(clean-files).
-
- Example:
- #drivers/pci/Makefile
- clean-files := devlist.h classlist.h
-
-When executing "make clean", the two files "devlist.h classlist.h" will
-be deleted. Kbuild will assume files to be in same relative directory as the
-Makefile except if an absolute path is specified (path starting with '/').
-
-To delete a directory hierarchy use:
-
- Example:
- #scripts/package/Makefile
- clean-dirs := $(objtree)/debian/
-
-This will delete the directory debian, including all subdirectories.
-Kbuild will assume the directories to be in the same relative path as the
-Makefile if no absolute path is specified (path does not start with '/').
-
-To exclude certain files from make clean, use the $(no-clean-files) variable.
-This is only a special case used in the top level Kbuild file:
-
- Example:
- #Kbuild
- no-clean-files := $(bounds-file) $(offsets-file)
-
-Usually kbuild descends down in subdirectories due to "obj-* := dir/",
-but in the architecture makefiles where the kbuild infrastructure
-is not sufficient this sometimes needs to be explicit.
-
- Example:
- #arch/x86/boot/Makefile
- subdir- := compressed/
-
-The above assignment instructs kbuild to descend down in the
-directory compressed/ when "make clean" is executed.
-
-To support the clean infrastructure in the Makefiles that builds the
-final bootimage there is an optional target named archclean:
-
- Example:
- #arch/x86/Makefile
- archclean:
- $(Q)$(MAKE) $(clean)=arch/x86/boot
-
-When "make clean" is executed, make will descend down in arch/x86/boot,
-and clean as usual. The Makefile located in arch/x86/boot/ may use
-the subdir- trick to descend further down.
-
-Note 1: arch/$(ARCH)/Makefile cannot use "subdir-", because that file is
-included in the top level makefile, and the kbuild infrastructure
-is not operational at that point.
-
-Note 2: All directories listed in core-y, libs-y, drivers-y and net-y will
-be visited during "make clean".
-
-=== 6 Architecture Makefiles
-
-The top level Makefile sets up the environment and does the preparation,
-before starting to descend down in the individual directories.
-The top level makefile contains the generic part, whereas
-arch/$(ARCH)/Makefile contains what is required to set up kbuild
-for said architecture.
-To do so, arch/$(ARCH)/Makefile sets up a number of variables and defines
-a few targets.
-
-When kbuild executes, the following steps are followed (roughly):
-1) Configuration of the kernel => produce .config
-2) Store kernel version in include/linux/version.h
-3) Symlink include/asm to include/asm-$(ARCH)
-4) Updating all other prerequisites to the target prepare:
- - Additional prerequisites are specified in arch/$(ARCH)/Makefile
-5) Recursively descend down in all directories listed in
- init-* core* drivers-* net-* libs-* and build all targets.
- - The values of the above variables are expanded in arch/$(ARCH)/Makefile.
-6) All object files are then linked and the resulting file vmlinux is
- located at the root of the obj tree.
- The very first objects linked are listed in head-y, assigned by
- arch/$(ARCH)/Makefile.
-7) Finally, the architecture-specific part does any required post processing
- and builds the final bootimage.
- - This includes building boot records
- - Preparing initrd images and the like
-
-
---- 6.1 Set variables to tweak the build to the architecture
-
- LDFLAGS Generic $(LD) options
-
- Flags used for all invocations of the linker.
- Often specifying the emulation is sufficient.
-
- Example:
- #arch/s390/Makefile
- LDFLAGS := -m elf_s390
- Note: ldflags-y can be used to further customise
- the flags used. See chapter 3.7.
-
- LDFLAGS_MODULE Options for $(LD) when linking modules
-
- LDFLAGS_MODULE is used to set specific flags for $(LD) when
- linking the .ko files used for modules.
- Default is "-r", for relocatable output.
-
- LDFLAGS_vmlinux Options for $(LD) when linking vmlinux
-
- LDFLAGS_vmlinux is used to specify additional flags to pass to
- the linker when linking the final vmlinux image.
- LDFLAGS_vmlinux uses the LDFLAGS_$@ support.
-
- Example:
- #arch/x86/Makefile
- LDFLAGS_vmlinux := -e stext
-
- OBJCOPYFLAGS objcopy flags
-
- When $(call if_changed,objcopy) is used to translate a .o file,
- the flags specified in OBJCOPYFLAGS will be used.
- $(call if_changed,objcopy) is often used to generate raw binaries on
- vmlinux.
-
- Example:
- #arch/s390/Makefile
- OBJCOPYFLAGS := -O binary
-
- #arch/s390/boot/Makefile
- $(obj)/image: vmlinux FORCE
- $(call if_changed,objcopy)
-
- In this example, the binary $(obj)/image is a binary version of
- vmlinux. The usage of $(call if_changed,xxx) will be described later.
-
- KBUILD_AFLAGS $(AS) assembler flags
-
- Default value - see top level Makefile
- Append or modify as required per architecture.
-
- Example:
- #arch/sparc64/Makefile
- KBUILD_AFLAGS += -m64 -mcpu=ultrasparc
-
- KBUILD_CFLAGS $(CC) compiler flags
-
- Default value - see top level Makefile
- Append or modify as required per architecture.
-
- Often, the KBUILD_CFLAGS variable depends on the configuration.
-
- Example:
- #arch/x86/Makefile
- cflags-$(CONFIG_M386) += -march=i386
- KBUILD_CFLAGS += $(cflags-y)
-
- Many arch Makefiles dynamically run the target C compiler to
- probe supported options:
-
- #arch/x86/Makefile
-
- ...
- cflags-$(CONFIG_MPENTIUMII) += $(call cc-option,\
- -march=pentium2,-march=i686)
- ...
- # Disable unit-at-a-time mode ...
- KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time)
- ...
-
-
- The first example utilises the trick that a config option expands
- to 'y' when selected.
-
- KBUILD_AFLAGS_KERNEL $(AS) options specific for built-in
-
- $(KBUILD_AFLAGS_KERNEL) contains extra C compiler flags used to compile
- resident kernel code.
-
- KBUILD_AFLAGS_MODULE Options for $(AS) when building modules
-
- $(KBUILD_AFLAGS_MODULE) is used to add arch specific options that
- are used for $(AS).
- From commandline AFLAGS_MODULE shall be used (see kbuild.txt).
-
- KBUILD_CFLAGS_KERNEL $(CC) options specific for built-in
-
- $(KBUILD_CFLAGS_KERNEL) contains extra C compiler flags used to compile
- resident kernel code.
-
- KBUILD_CFLAGS_MODULE Options for $(CC) when building modules
-
- $(KBUILD_CFLAGS_MODULE) is used to add arch specific options that
- are used for $(CC).
- From commandline CFLAGS_MODULE shall be used (see kbuild.txt).
-
- KBUILD_LDFLAGS_MODULE Options for $(LD) when linking modules
-
- $(KBUILD_LDFLAGS_MODULE) is used to add arch specific options
- used when linking modules. This is often a linker script.
- From commandline LDFLAGS_MODULE shall be used (see kbuild.txt).
-
- KBUILD_ARFLAGS Options for $(AR) when creating archives
-
- $(KBUILD_ARFLAGS) set by the top level Makefile to "D" (deterministic
- mode) if this option is supported by $(AR).
-
---- 6.2 Add prerequisites to archheaders:
-
- The archheaders: rule is used to generate header files that
- may be installed into user space by "make header_install" or
- "make headers_install_all". In order to support
- "make headers_install_all", this target has to be able to run
- on an unconfigured tree, or a tree configured for another
- architecture.
-
- It is run before "make archprepare" when run on the
- architecture itself.
-
-
---- 6.3 Add prerequisites to archprepare:
-
- The archprepare: rule is used to list prerequisites that need to be
- built before starting to descend down in the subdirectories.
- This is usually used for header files containing assembler constants.
-
- Example:
- #arch/arm/Makefile
- archprepare: maketools
-
- In this example, the file target maketools will be processed
- before descending down in the subdirectories.
- See also chapter XXX-TODO that describe how kbuild supports
- generating offset header files.
-
-
---- 6.4 List directories to visit when descending
-
- An arch Makefile cooperates with the top Makefile to define variables
- which specify how to build the vmlinux file. Note that there is no
- corresponding arch-specific section for modules; the module-building
- machinery is all architecture-independent.
-
-
- head-y, init-y, core-y, libs-y, drivers-y, net-y
-
- $(head-y) lists objects to be linked first in vmlinux.
- $(libs-y) lists directories where a lib.a archive can be located.
- The rest list directories where a built-in.o object file can be
- located.
-
- $(init-y) objects will be located after $(head-y).
- Then the rest follows in this order:
- $(core-y), $(libs-y), $(drivers-y) and $(net-y).
-
- The top level Makefile defines values for all generic directories,
- and arch/$(ARCH)/Makefile only adds architecture-specific directories.
-
- Example:
- #arch/sparc64/Makefile
- core-y += arch/sparc64/kernel/
- libs-y += arch/sparc64/prom/ arch/sparc64/lib/
- drivers-$(CONFIG_OPROFILE) += arch/sparc64/oprofile/
-
-
---- 6.5 Architecture-specific boot images
-
- An arch Makefile specifies goals that take the vmlinux file, compress
- it, wrap it in bootstrapping code, and copy the resulting files
- somewhere. This includes various kinds of installation commands.
- The actual goals are not standardized across architectures.
-
- It is common to locate any additional processing in a boot/
- directory below arch/$(ARCH)/.
-
- Kbuild does not provide any smart way to support building a
- target specified in boot/. Therefore arch/$(ARCH)/Makefile shall
- call make manually to build a target in boot/.
-
- The recommended approach is to include shortcuts in
- arch/$(ARCH)/Makefile, and use the full path when calling down
- into the arch/$(ARCH)/boot/Makefile.
-
- Example:
- #arch/x86/Makefile
- boot := arch/x86/boot
- bzImage: vmlinux
- $(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
-
- "$(Q)$(MAKE) $(build)=<dir>" is the recommended way to invoke
- make in a subdirectory.
-
- There are no rules for naming architecture-specific targets,
- but executing "make help" will list all relevant targets.
- To support this, $(archhelp) must be defined.
-
- Example:
- #arch/x86/Makefile
- define archhelp
- echo '* bzImage - Image (arch/$(ARCH)/boot/bzImage)'
- endif
-
- When make is executed without arguments, the first goal encountered
- will be built. In the top level Makefile the first goal present
- is all:.
- An architecture shall always, per default, build a bootable image.
- In "make help", the default goal is highlighted with a '*'.
- Add a new prerequisite to all: to select a default goal different
- from vmlinux.
-
- Example:
- #arch/x86/Makefile
- all: bzImage
-
- When "make" is executed without arguments, bzImage will be built.
-
---- 6.6 Building non-kbuild targets
-
- extra-y
-
- extra-y specify additional targets created in the current
- directory, in addition to any targets specified by obj-*.
-
- Listing all targets in extra-y is required for two purposes:
- 1) Enable kbuild to check changes in command lines
- - When $(call if_changed,xxx) is used
- 2) kbuild knows what files to delete during "make clean"
-
- Example:
- #arch/x86/kernel/Makefile
- extra-y := head.o init_task.o
-
- In this example, extra-y is used to list object files that
- shall be built, but shall not be linked as part of built-in.o.
-
-
---- 6.7 Commands useful for building a boot image
-
- Kbuild provides a few macros that are useful when building a
- boot image.
-
- if_changed
-
- if_changed is the infrastructure used for the following commands.
-
- Usage:
- target: source(s) FORCE
- $(call if_changed,ld/objcopy/gzip)
-
- When the rule is evaluated, it is checked to see if any files
- need an update, or the command line has changed since the last
- invocation. The latter will force a rebuild if any options
- to the executable have changed.
- Any target that utilises if_changed must be listed in $(targets),
- otherwise the command line check will fail, and the target will
- always be built.
- Assignments to $(targets) are without $(obj)/ prefix.
- if_changed may be used in conjunction with custom commands as
- defined in 6.8 "Custom kbuild commands".
-
- Note: It is a typical mistake to forget the FORCE prerequisite.
- Another common pitfall is that whitespace is sometimes
- significant; for instance, the below will fail (note the extra space
- after the comma):
- target: source(s) FORCE
- #WRONG!# $(call if_changed, ld/objcopy/gzip)
-
- ld
- Link target. Often, LDFLAGS_$@ is used to set specific options to ld.
-
- objcopy
- Copy binary. Uses OBJCOPYFLAGS usually specified in
- arch/$(ARCH)/Makefile.
- OBJCOPYFLAGS_$@ may be used to set additional options.
-
- gzip
- Compress target. Use maximum compression to compress target.
-
- Example:
- #arch/x86/boot/Makefile
- LDFLAGS_bootsect := -Ttext 0x0 -s --oformat binary
- LDFLAGS_setup := -Ttext 0x0 -s --oformat binary -e begtext
-
- targets += setup setup.o bootsect bootsect.o
- $(obj)/setup $(obj)/bootsect: %: %.o FORCE
- $(call if_changed,ld)
-
- In this example, there are two possible targets, requiring different
- options to the linker. The linker options are specified using the
- LDFLAGS_$@ syntax - one for each potential target.
- $(targets) are assigned all potential targets, by which kbuild knows
- the targets and will:
- 1) check for commandline changes
- 2) delete target during make clean
-
- The ": %: %.o" part of the prerequisite is a shorthand that
- free us from listing the setup.o and bootsect.o files.
- Note: It is a common mistake to forget the "target :=" assignment,
- resulting in the target file being recompiled for no
- obvious reason.
-
- dtc
- Create flattend device tree blob object suitable for linking
- into vmlinux. Device tree blobs linked into vmlinux are placed
- in an init section in the image. Platform code *must* copy the
- blob to non-init memory prior to calling unflatten_device_tree().
-
- Example:
- #arch/x86/platform/ce4100/Makefile
- clean-files := *dtb.S
-
- DTC_FLAGS := -p 1024
- obj-y += foo.dtb.o
-
- $(obj)/%.dtb: $(src)/%.dts
- $(call cmd,dtc)
-
---- 6.8 Custom kbuild commands
-
- When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand
- of a command is normally displayed.
- To enable this behaviour for custom commands kbuild requires
- two variables to be set:
- quiet_cmd_<command> - what shall be echoed
- cmd_<command> - the command to execute
-
- Example:
- #
- quiet_cmd_image = BUILD $@
- cmd_image = $(obj)/tools/build $(BUILDFLAGS) \
- $(obj)/vmlinux.bin > $@
-
- targets += bzImage
- $(obj)/bzImage: $(obj)/vmlinux.bin $(obj)/tools/build FORCE
- $(call if_changed,image)
- @echo 'Kernel: $@ is ready'
-
- When updating the $(obj)/bzImage target, the line
-
- BUILD arch/x86/boot/bzImage
-
- will be displayed with "make KBUILD_VERBOSE=0".
-
-
---- 6.9 Preprocessing linker scripts
-
- When the vmlinux image is built, the linker script
- arch/$(ARCH)/kernel/vmlinux.lds is used.
- The script is a preprocessed variant of the file vmlinux.lds.S
- located in the same directory.
- kbuild knows .lds files and includes a rule *lds.S -> *lds.
-
- Example:
- #arch/x86/kernel/Makefile
- always := vmlinux.lds
-
- #Makefile
- export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH)
-
- The assignment to $(always) is used to tell kbuild to build the
- target vmlinux.lds.
- The assignment to $(CPPFLAGS_vmlinux.lds) tells kbuild to use the
- specified options when building the target vmlinux.lds.
-
- When building the *.lds target, kbuild uses the variables:
- KBUILD_CPPFLAGS : Set in top-level Makefile
- cppflags-y : May be set in the kbuild makefile
- CPPFLAGS_$(@F) : Target specific flags.
- Note that the full filename is used in this
- assignment.
-
- The kbuild infrastructure for *lds file are used in several
- architecture-specific files.
-
---- 6.10 Generic header files
-
- The directory include/asm-generic contains the header files
- that may be shared between individual architectures.
- The recommended approach how to use a generic header file is
- to list the file in the Kbuild file.
- See "7.4 generic-y" for further info on syntax etc.
-
-=== 7 Kbuild syntax for exported headers
-
-The kernel include a set of headers that is exported to userspace.
-Many headers can be exported as-is but other headers require a
-minimal pre-processing before they are ready for user-space.
-The pre-processing does:
-- drop kernel specific annotations
-- drop include of compiler.h
-- drop all sections that are kernel internal (guarded by ifdef __KERNEL__)
-
-Each relevant directory contains a file name "Kbuild" which specifies the
-headers to be exported.
-See subsequent chapter for the syntax of the Kbuild file.
-
- --- 7.1 header-y
-
- header-y specify header files to be exported.
-
- Example:
- #include/linux/Kbuild
- header-y += usb/
- header-y += aio_abi.h
-
- The convention is to list one file per line and
- preferably in alphabetic order.
-
- header-y also specify which subdirectories to visit.
- A subdirectory is identified by a trailing '/' which
- can be seen in the example above for the usb subdirectory.
-
- Subdirectories are visited before their parent directories.
-
- --- 7.2 objhdr-y
-
- objhdr-y specifies generated files to be exported.
- Generated files are special as they need to be looked
- up in another directory when doing 'make O=...' builds.
-
- Example:
- #include/linux/Kbuild
- objhdr-y += version.h
-
- --- 7.3 destination-y
-
- When an architecture have a set of exported headers that needs to be
- exported to a different directory destination-y is used.
- destination-y specify the destination directory for all exported
- headers in the file where it is present.
-
- Example:
- #arch/xtensa/platforms/s6105/include/platform/Kbuild
- destination-y := include/linux
-
- In the example above all exported headers in the Kbuild file
- will be located in the directory "include/linux" when exported.
-
- --- 7.4 generic-y
-
- If an architecture uses a verbatim copy of a header from
- include/asm-generic then this is listed in the file
- arch/$(ARCH)/include/asm/Kbuild like this:
-
- Example:
- #arch/x86/include/asm/Kbuild
- generic-y += termios.h
- generic-y += rtc.h
-
- During the prepare phase of the build a wrapper include
- file is generated in the directory:
-
- arch/$(ARCH)/include/generated/asm
-
- When a header is exported where the architecture uses
- the generic header a similar wrapper is generated as part
- of the set of exported headers in the directory:
-
- usr/include/asm
-
- The generated wrapper will in both cases look like the following:
-
- Example: termios.h
- #include <asm-generic/termios.h>
-
-=== 8 Kbuild Variables
-
-The top Makefile exports the following variables:
-
- VERSION, PATCHLEVEL, SUBLEVEL, EXTRAVERSION
-
- These variables define the current kernel version. A few arch
- Makefiles actually use these values directly; they should use
- $(KERNELRELEASE) instead.
-
- $(VERSION), $(PATCHLEVEL), and $(SUBLEVEL) define the basic
- three-part version number, such as "2", "4", and "0". These three
- values are always numeric.
-
- $(EXTRAVERSION) defines an even tinier sublevel for pre-patches
- or additional patches. It is usually some non-numeric string
- such as "-pre4", and is often blank.
-
- KERNELRELEASE
-
- $(KERNELRELEASE) is a single string such as "2.4.0-pre4", suitable
- for constructing installation directory names or showing in
- version strings. Some arch Makefiles use it for this purpose.
-
- ARCH
-
- This variable defines the target architecture, such as "i386",
- "arm", or "sparc". Some kbuild Makefiles test $(ARCH) to
- determine which files to compile.
-
- By default, the top Makefile sets $(ARCH) to be the same as the
- host system architecture. For a cross build, a user may
- override the value of $(ARCH) on the command line:
-
- make ARCH=m68k ...
-
-
- INSTALL_PATH
-
- This variable defines a place for the arch Makefiles to install
- the resident kernel image and System.map file.
- Use this for architecture-specific install targets.
-
- INSTALL_MOD_PATH, MODLIB
-
- $(INSTALL_MOD_PATH) specifies a prefix to $(MODLIB) for module
- installation. This variable is not defined in the Makefile but
- may be passed in by the user if desired.
-
- $(MODLIB) specifies the directory for module installation.
- The top Makefile defines $(MODLIB) to
- $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE). The user may
- override this value on the command line if desired.
-
- INSTALL_MOD_STRIP
-
- If this variable is specified, 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 option(s) to the strip
- command.
-
-
-=== 9 Makefile language
-
-The kernel Makefiles are designed to be run with GNU Make. The Makefiles
-use only the documented features of GNU Make, but they do use many
-GNU extensions.
-
-GNU Make supports elementary list-processing functions. The kernel
-Makefiles use a novel style of list building and manipulation with few
-"if" statements.
-
-GNU Make has two assignment operators, ":=" and "=". ":=" performs
-immediate evaluation of the right-hand side and stores an actual string
-into the left-hand side. "=" is like a formula definition; it stores the
-right-hand side in an unevaluated form and then evaluates this form each
-time the left-hand side is used.
-
-There are some cases where "=" is appropriate. Usually, though, ":="
-is the right choice.
-
-=== 10 Credits
-
-Original version made by Michael Elizabeth Chastain, <mailto:mec@shout.net>
-Updates by Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de>
-Updates by Sam Ravnborg <sam@ravnborg.org>
-Language QA by Jan Engelhardt <jengelh@gmx.de>
-
-=== 11 TODO
-
-- Describe how kbuild supports shipped files with _shipped.
-- Generating offset header files.
-- Add more variables to section 7?
-
-
-
diff --git a/Documentation/kbuild/modules.txt b/Documentation/kbuild/modules.txt
deleted file mode 100644
index 3fb39e0116b..00000000000
--- a/Documentation/kbuild/modules.txt
+++ /dev/null
@@ -1,541 +0,0 @@
-Building External Modules
-
-This document describes how to build an out-of-tree kernel module.
-
-=== Table of Contents
-
- === 1 Introduction
- === 2 How to Build External Modules
- --- 2.1 Command Syntax
- --- 2.2 Options
- --- 2.3 Targets
- --- 2.4 Building Separate Files
- === 3. Creating a Kbuild File for an External Module
- --- 3.1 Shared Makefile
- --- 3.2 Separate Kbuild file and Makefile
- --- 3.3 Binary Blobs
- --- 3.4 Building Multiple Modules
- === 4. Include Files
- --- 4.1 Kernel Includes
- --- 4.2 Single Subdirectory
- --- 4.3 Several Subdirectories
- === 5. Module Installation
- --- 5.1 INSTALL_MOD_PATH
- --- 5.2 INSTALL_MOD_DIR
- === 6. Module Versioning
- --- 6.1 Symbols From the Kernel (vmlinux + modules)
- --- 6.2 Symbols and External Modules
- --- 6.3 Symbols From Another External Module
- === 7. Tips & Tricks
- --- 7.1 Testing for CONFIG_FOO_BAR
-
-
-
-=== 1. Introduction
-
-"kbuild" is the build system used by the Linux kernel. Modules must use
-kbuild to stay compatible with changes in the build infrastructure and
-to pick up the right flags to "gcc." Functionality for building modules
-both in-tree and out-of-tree is provided. The method for building
-either is similar, and all modules are initially developed and built
-out-of-tree.
-
-Covered in this document is information aimed at developers interested
-in building out-of-tree (or "external") modules. The author of an
-external module should supply a makefile that hides most of the
-complexity, so one only has to type "make" to build the module. This is
-easily accomplished, and a complete example will be presented in
-section 3.
-
-
-=== 2. How to Build External Modules
-
-To build external modules, you must have a prebuilt kernel available
-that contains the configuration and header files used in the build.
-Also, the kernel must have been built with modules enabled. If you are
-using a distribution kernel, there will be a package for the kernel you
-are running provided by your distribution.
-
-An alternative is to use the "make" target "modules_prepare." This will
-make sure the kernel contains the information required. The target
-exists solely as a simple way to prepare a kernel source tree for
-building external modules.
-
-NOTE: "modules_prepare" will not build Module.symvers even if
-CONFIG_MODVERSIONS is set; therefore, a full kernel build needs to be
-executed to make module versioning work.
-
---- 2.1 Command Syntax
-
- The command to build an external module is:
-
- $ make -C <path_to_kernel_src> M=$PWD
-
- The kbuild system knows that an external module is being built
- due to the "M=<dir>" option given in the command.
-
- To build against the running kernel use:
-
- $ make -C /lib/modules/`uname -r`/build M=$PWD
-
- Then to install the module(s) just built, add the target
- "modules_install" to the command:
-
- $ make -C /lib/modules/`uname -r`/build M=$PWD modules_install
-
---- 2.2 Options
-
- ($KDIR refers to the path of the kernel source directory.)
-
- make -C $KDIR M=$PWD
-
- -C $KDIR
- The directory where the kernel source is located.
- "make" will actually change to the specified directory
- when executing and will change back when finished.
-
- M=$PWD
- Informs kbuild that an external module is being built.
- The value given to "M" is the absolute path of the
- directory where the external module (kbuild file) is
- located.
-
---- 2.3 Targets
-
- When building an external module, only a subset of the "make"
- targets are available.
-
- make -C $KDIR M=$PWD [target]
-
- The default will build the module(s) located in the current
- directory, so a target does not need to be specified. All
- output files will also be generated in this directory. No
- attempts are made to update the kernel source, and it is a
- precondition that a successful "make" has been executed for the
- kernel.
-
- modules
- The default target for external modules. It has the
- same functionality as if no target was specified. See
- description above.
-
- modules_install
- Install the external module(s). The default location is
- /lib/modules/<kernel_release>/extra/, but a prefix may
- be added with INSTALL_MOD_PATH (discussed in section 5).
-
- clean
- Remove all generated files in the module directory only.
-
- help
- List the available targets for external modules.
-
---- 2.4 Building Separate Files
-
- It is possible to build single files that are part of a module.
- This works equally well for the kernel, a module, and even for
- external modules.
-
- Example (The module foo.ko, consist of bar.o and baz.o):
- make -C $KDIR M=$PWD bar.lst
- make -C $KDIR M=$PWD baz.o
- make -C $KDIR M=$PWD foo.ko
- make -C $KDIR M=$PWD /
-
-
-=== 3. Creating a Kbuild File for an External Module
-
-In the last section we saw the command to build a module for the
-running kernel. The module is not actually built, however, because a
-build file is required. Contained in this file will be the name of
-the module(s) being built, along with the list of requisite source
-files. The file may be as simple as a single line:
-
- obj-m := <module_name>.o
-
-The kbuild system will build <module_name>.o from <module_name>.c,
-and, after linking, will result in the kernel module <module_name>.ko.
-The above line can be put in either a "Kbuild" file or a "Makefile."
-When the module is built from multiple sources, an additional line is
-needed listing the files:
-
- <module_name>-y := <src1>.o <src2>.o ...
-
-NOTE: Further documentation describing the syntax used by kbuild is
-located in Documentation/kbuild/makefiles.txt.
-
-The examples below demonstrate how to create a build file for the
-module 8123.ko, which is built from the following files:
-
- 8123_if.c
- 8123_if.h
- 8123_pci.c
- 8123_bin.o_shipped <= Binary blob
-
---- 3.1 Shared Makefile
-
- An external module always includes a wrapper makefile that
- supports building the module using "make" with no arguments.
- This target is not used by kbuild; it is only for convenience.
- Additional functionality, such as test targets, can be included
- but should be filtered out from kbuild due to possible name
- clashes.
-
- Example 1:
- --> filename: Makefile
- ifneq ($(KERNELRELEASE),)
- # kbuild part of makefile
- obj-m := 8123.o
- 8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
- else
- # normal makefile
- KDIR ?= /lib/modules/`uname -r`/build
-
- default:
- $(MAKE) -C $(KDIR) M=$$PWD
-
- # Module specific targets
- genbin:
- echo "X" > 8123_bin.o_shipped
-
- endif
-
- The check for KERNELRELEASE is used to separate the two parts
- of the makefile. In the example, kbuild will only see the two
- assignments, whereas "make" will see everything except these
- two assignments. This is due to two passes made on the file:
- the first pass is by the "make" instance run on the command
- line; the second pass is by the kbuild system, which is
- initiated by the parameterized "make" in the default target.
-
---- 3.2 Separate Kbuild File and Makefile
-
- In newer versions of the kernel, kbuild will first look for a
- file named "Kbuild," and only if that is not found, will it
- then look for a makefile. Utilizing a "Kbuild" file allows us
- to split up the makefile from example 1 into two files:
-
- Example 2:
- --> filename: Kbuild
- obj-m := 8123.o
- 8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
- --> filename: Makefile
- KDIR ?= /lib/modules/`uname -r`/build
-
- default:
- $(MAKE) -C $(KDIR) M=$$PWD
-
- # Module specific targets
- genbin:
- echo "X" > 8123_bin.o_shipped
-
- The split in example 2 is questionable due to the simplicity of
- each file; however, some external modules use makefiles
- consisting of several hundred lines, and here it really pays
- off to separate the kbuild part from the rest.
-
- The next example shows a backward compatible version.
-
- Example 3:
- --> filename: Kbuild
- obj-m := 8123.o
- 8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
- --> filename: Makefile
- ifneq ($(KERNELRELEASE),)
- # kbuild part of makefile
- include Kbuild
-
- else
- # normal makefile
- KDIR ?= /lib/modules/`uname -r`/build
-
- default:
- $(MAKE) -C $(KDIR) M=$$PWD
-
- # Module specific targets
- genbin:
- echo "X" > 8123_bin.o_shipped
-
- endif
-
- Here the "Kbuild" file is included from the makefile. This
- allows an older version of kbuild, which only knows of
- makefiles, to be used when the "make" and kbuild parts are
- split into separate files.
-
---- 3.3 Binary Blobs
-
- Some external modules need to include an object file as a blob.
- kbuild has support for this, but requires the blob file to be
- named <filename>_shipped. When the kbuild rules kick in, a copy
- of <filename>_shipped is created with _shipped stripped off,
- giving us <filename>. This shortened filename can be used in
- the assignment to the module.
-
- Throughout this section, 8123_bin.o_shipped has been used to
- build the kernel module 8123.ko; it has been included as
- 8123_bin.o.
-
- 8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
- Although there is no distinction between the ordinary source
- files and the binary file, kbuild will pick up different rules
- when creating the object file for the module.
-
---- 3.4 Building Multiple Modules
-
- kbuild supports building multiple modules with a single build
- file. For example, if you wanted to build two modules, foo.ko
- and bar.ko, the kbuild lines would be:
-
- obj-m := foo.o bar.o
- foo-y := <foo_srcs>
- bar-y := <bar_srcs>
-
- It is that simple!
-
-
-=== 4. Include Files
-
-Within the kernel, header files are kept in standard locations
-according to the following rule:
-
- * If the header file only describes the internal interface of a
- module, then the file is placed in the same directory as the
- source files.
- * If the header file describes an interface used by other parts
- of the kernel that are located in different directories, then
- the file is placed in include/linux/.
-
- NOTE: There are two notable exceptions to this rule: larger
- subsystems have their own directory under include/, such as
- include/scsi; and architecture specific headers are located
- under arch/$(ARCH)/include/.
-
---- 4.1 Kernel Includes
-
- To include a header file located under include/linux/, simply
- use:
-
- #include <linux/module.h>
-
- kbuild will add options to "gcc" so the relevant directories
- are searched.
-
---- 4.2 Single Subdirectory
-
- External modules tend to place header files in a separate
- include/ directory where their source is located, although this
- is not the usual kernel style. To inform kbuild of the
- directory, use either ccflags-y or CFLAGS_<filename>.o.
-
- Using the example from section 3, if we moved 8123_if.h to a
- subdirectory named include, the resulting kbuild file would
- look like:
-
- --> filename: Kbuild
- obj-m := 8123.o
-
- ccflags-y := -Iinclude
- 8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
- Note that in the assignment there is no space between -I and
- the path. This is a limitation of kbuild: there must be no
- space present.
-
---- 4.3 Several Subdirectories
-
- kbuild can handle files that are spread over several directories.
- Consider the following example:
-
- .
- |__ src
- | |__ complex_main.c
- | |__ hal
- | |__ hardwareif.c
- | |__ include
- | |__ hardwareif.h
- |__ include
- |__ complex.h
-
- To build the module complex.ko, we then need the following
- kbuild file:
-
- --> filename: Kbuild
- obj-m := complex.o
- complex-y := src/complex_main.o
- complex-y += src/hal/hardwareif.o
-
- ccflags-y := -I$(src)/include
- ccflags-y += -I$(src)/src/hal/include
-
- As you can see, kbuild knows how to handle object files located
- in other directories. The trick is to specify the directory
- relative to the kbuild file's location. That being said, this
- is NOT recommended practice.
-
- For the header files, kbuild must be explicitly told where to
- look. When kbuild executes, the current directory is always the
- root of the kernel tree (the argument to "-C") and therefore an
- absolute path is needed. $(src) provides the absolute path by
- pointing to the directory where the currently executing kbuild
- file is located.
-
-
-=== 5. Module Installation
-
-Modules which are included in the kernel are installed in the
-directory:
-
- /lib/modules/$(KERNELRELEASE)/kernel/
-
-And external modules are installed in:
-
- /lib/modules/$(KERNELRELEASE)/extra/
-
---- 5.1 INSTALL_MOD_PATH
-
- Above are the default directories but as always some level of
- customization is possible. A prefix can be added to the
- installation path using the variable INSTALL_MOD_PATH:
-
- $ make INSTALL_MOD_PATH=/frodo modules_install
- => Install dir: /frodo/lib/modules/$(KERNELRELEASE)/kernel/
-
- INSTALL_MOD_PATH may be set as an ordinary shell variable or,
- as shown above, can be specified on the command line when
- calling "make." This has effect when installing both in-tree
- and out-of-tree modules.
-
---- 5.2 INSTALL_MOD_DIR
-
- External modules are by default installed to a directory under
- /lib/modules/$(KERNELRELEASE)/extra/, but you may wish to
- locate modules for a specific functionality in a separate
- directory. For this purpose, use INSTALL_MOD_DIR to specify an
- alternative name to "extra."
-
- $ make INSTALL_MOD_DIR=gandalf -C $KDIR \
- M=$PWD modules_install
- => Install dir: /lib/modules/$(KERNELRELEASE)/gandalf/
-
-
-=== 6. Module Versioning
-
-Module versioning is enabled by the CONFIG_MODVERSIONS tag, and is used
-as a simple ABI consistency check. A CRC value of the full prototype
-for an exported symbol is created. When a module is loaded/used, the
-CRC values contained in the kernel are compared with similar values in
-the module; if they are not equal, the kernel refuses to load the
-module.
-
-Module.symvers contains a list of all exported symbols from a kernel
-build.
-
---- 6.1 Symbols From the Kernel (vmlinux + modules)
-
- During a kernel build, a file named Module.symvers will be
- generated. Module.symvers contains all exported symbols from
- the kernel and compiled modules. For each symbol, the
- corresponding CRC value is also stored.
-
- The syntax of the Module.symvers file is:
- <CRC> <Symbol> <module>
-
- 0x2d036834 scsi_remove_host drivers/scsi/scsi_mod
-
- For a kernel build without CONFIG_MODVERSIONS enabled, the CRC
- would read 0x00000000.
-
- Module.symvers serves two purposes:
- 1) It lists all exported symbols from vmlinux and all modules.
- 2) It lists the CRC if CONFIG_MODVERSIONS is enabled.
-
---- 6.2 Symbols and External Modules
-
- When building an external module, the build system needs access
- to the symbols from the kernel to check if all external symbols
- are defined. This is done in the MODPOST step. modpost obtains
- the symbols by reading Module.symvers from the kernel source
- tree. If a Module.symvers file is present in the directory
- where the external module is being built, this file will be
- read too. During the MODPOST step, a new Module.symvers file
- will be written containing all exported symbols that were not
- defined in the kernel.
-
---- 6.3 Symbols From Another External Module
-
- Sometimes, an external module uses exported symbols from
- another external module. kbuild needs to have full knowledge of
- all symbols to avoid spitting out warnings about undefined
- symbols. Three solutions exist for this situation.
-
- NOTE: The method with a top-level kbuild file is recommended
- but may be impractical in certain situations.
-
- Use a top-level kbuild file
- If you have two modules, foo.ko and bar.ko, where
- foo.ko needs symbols from bar.ko, you can use a
- common top-level kbuild file so both modules are
- compiled in the same build. Consider the following
- directory layout:
-
- ./foo/ <= contains foo.ko
- ./bar/ <= contains bar.ko
-
- The top-level kbuild file would then look like:
-
- #./Kbuild (or ./Makefile):
- obj-y := foo/ bar/
-
- And executing
-
- $ make -C $KDIR M=$PWD
-
- will then do the expected and compile both modules with
- full knowledge of symbols from either module.
-
- Use an extra Module.symvers file
- When an external module is built, a Module.symvers file
- is generated containing all exported symbols which are
- not defined in the kernel. To get access to symbols
- from bar.ko, copy the Module.symvers file from the
- compilation of bar.ko to the directory where foo.ko is
- built. During the module build, kbuild will read the
- Module.symvers file in the directory of the external
- module, and when the build is finished, a new
- Module.symvers file is created containing the sum of
- all symbols defined and not part of the kernel.
-
- Use "make" variable KBUILD_EXTRA_SYMBOLS
- If it is impractical to copy Module.symvers from
- another module, you can assign a space separated list
- of files to KBUILD_EXTRA_SYMBOLS in your build file.
- These files will be loaded by modpost during the
- initialization of its symbol tables.
-
-
-=== 7. Tips & Tricks
-
---- 7.1 Testing for CONFIG_FOO_BAR
-
- Modules often need to check for certain CONFIG_ options to
- decide if a specific feature is included in the module. In
- kbuild this is done by referencing the CONFIG_ variable
- directly.
-
- #fs/ext2/Makefile
- obj-$(CONFIG_EXT2_FS) += ext2.o
-
- ext2-y := balloc.o bitmap.o dir.o
- ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o
-
- External modules have traditionally used "grep" to check for
- specific CONFIG_ settings directly in .config. This usage is
- broken. As introduced before, external modules should use
- kbuild for building and can therefore use the same methods as
- in-tree modules when testing for CONFIG_ definitions.
-