Merge tag 'kbuild-v5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

/linux

/vmlinux

/vmlinux.32

/vmlinux.symvers

/vmlinux-gdb.py

/vmlinuz

/System.map

vmlinux.aout

vmlinux.bin.all

vmlinux.lds

vmlinux.symvers

vmlinuz

voffset.h

vsyscall.lds

	   --- 4.4 Controlling compiler options for host programs

	   --- 4.5 When host programs are actually built

	=== 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

	   --- 6.11 Post-link pass

	=== 7 Kbuild syntax for exported headers

		--- 7.1 no-export-headers

		--- 7.2 generic-y

		--- 7.3 generated-y

		--- 7.4 mandatory-y

	=== 8 Kbuild Variables

	=== 9 Makefile language

	=== 10 Credits

	=== 11 TODO

	=== 5 Userspace Program support

	   --- 5.1 Simple Userspace Program

	   --- 5.2 Composite Userspace Programs

	   --- 5.3 Controlling compiler options for userspace programs

	   --- 5.4 When userspace programs are actually built

	=== 6 Kbuild clean infrastructure

	=== 7 Architecture Makefiles

	   --- 7.1 Set variables to tweak the build to the architecture

	   --- 7.2 Add prerequisites to archheaders:

	   --- 7.3 Add prerequisites to archprepare:

	   --- 7.4 List directories to visit when descending

	   --- 7.5 Architecture-specific boot images

	   --- 7.6 Building non-kbuild targets

	   --- 7.7 Commands useful for building a boot image

	   --- 7.8 Custom kbuild commands

	   --- 7.9 Preprocessing linker scripts

	   --- 7.10 Generic header files

	   --- 7.11 Post-link pass

	=== 8 Kbuild syntax for exported headers

		--- 8.1 no-export-headers

		--- 8.2 generic-y

		--- 8.3 generated-y

		--- 8.4 mandatory-y

	=== 9 Kbuild Variables

	=== 10 Makefile language

	=== 11 Credits

	=== 12 TODO

1 Overview

==========

	This will tell kbuild to build lxdialog even if not referenced in

	any rule.

5 Kbuild clean infrastructure

5 Userspace Program support

===========================

Just like host programs, Kbuild also supports building userspace executables

for the target architecture (i.e. the same architecture as you are building

the kernel for).

The syntax is quite similar. The difference is to use "userprogs" instead of

"hostprogs".

5.1 Simple Userspace Program

----------------------------

	The following line tells kbuild that the program bpf-direct shall be

	built for the target architecture.

	Example::

		userprogs := bpf-direct

	Kbuild assumes in the above example that bpf-direct is made from a

	single C source file named bpf-direct.c located in the same directory

	as the Makefile.

5.2 Composite Userspace Programs

--------------------------------

	Userspace programs can be made up based on composite objects.

	The syntax used to define composite objects for userspace programs is

	similar to the syntax used for kernel objects.

	$(<executable>-objs) lists all objects used to link the final

	executable.

	Example::

		#samples/seccomp/Makefile

		userprogs      := bpf-fancy

		bpf-fancy-objs := bpf-fancy.o bpf-helper.o

	Objects with extension .o are compiled from the corresponding .c

	files. In the above example, bpf-fancy.c is compiled to bpf-fancy.o

	and bpf-helper.c is compiled to bpf-helper.o.

	Finally, the two .o files are linked to the executable, bpf-fancy.

	Note: The syntax <executable>-y is not permitted for userspace programs.

5.3 Controlling compiler options for userspace programs

-------------------------------------------------------

	When compiling userspace programs, it is possible to set specific flags.

	The programs will always be compiled utilising $(CC) passed

	the options specified in $(KBUILD_USERCFLAGS).

	To set flags that will take effect for all userspace programs created

	in that Makefile, use the variable userccflags.

	Example::

		# samples/seccomp/Makefile

		userccflags += -I usr/include

	To set specific flags for a single file the following construction

	is used:

	Example::

		bpf-helper-userccflags += -I user/include

	It is also possible to specify additional options to the linker.

	Example::

		# net/bpfilter/Makefile

		bpfilter_umh-userldflags += -static

	When linking bpfilter_umh, it will be passed the extra option -static.

5.4 When userspace programs are actually built

----------------------------------------------

	Same as "When host programs are actually built".

6 Kbuild clean infrastructure

=============================

"make clean" deletes most generated files in the obj tree where the kernel

Note 2: All directories listed in core-y, libs-y, drivers-y and net-y will

be visited during "make clean".

6 Architecture Makefiles

7 Architecture Makefiles

========================

The top level Makefile sets up the environment and does the preparation,

   - Preparing initrd images and the like

6.1 Set variables to tweak the build to the architecture

7.1 Set variables to tweak the build to the architecture

--------------------------------------------------------

    LDFLAGS

    KBUILD_LDFLAGS

	Generic $(LD) options

	Flags used for all invocations of the linker.

	Example::

		#arch/s390/Makefile

		LDFLAGS         := -m elf_s390

		KBUILD_LDFLAGS         := -m elf_s390

	Note: ldflags-y can be used to further customise

	the flags used. See chapter 3.7.

	KBUILD_VMLINUX_LIBS together specify all the object files used to

	link vmlinux.

6.2 Add prerequisites to archheaders

7.2 Add prerequisites to archheaders

------------------------------------

	The archheaders: rule is used to generate header files that

	architecture itself.

6.3 Add prerequisites to archprepare

7.3 Add prerequisites to archprepare

------------------------------------

	The archprepare: rule is used to list prerequisites that need to be

	generating offset header files.

6.4 List directories to visit when descending

7.4 List directories to visit when descending

---------------------------------------------

	An arch Makefile cooperates with the top Makefile to define variables

		drivers-$(CONFIG_OPROFILE)  += arch/sparc64/oprofile/

6.5 Architecture-specific boot images

7.5 Architecture-specific boot images

-------------------------------------

	An arch Makefile specifies goals that take the vmlinux file, compress

	When "make" is executed without arguments, bzImage will be built.

6.6 Building non-kbuild targets

7.6 Building non-kbuild targets

-------------------------------

    extra-y

	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.a.

6.7 Commands useful for building a boot image

7.7 Commands useful for building a boot image

---------------------------------------------

    Kbuild provides a few macros that are useful when building a

		targets += $(dtb-y)

		DTC_FLAGS ?= -p 1024

6.8 Custom kbuild commands

7.8 Custom kbuild commands

--------------------------

	When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand

	will be displayed with "make KBUILD_VERBOSE=0".

6.9 Preprocessing linker scripts

7.9 Preprocessing linker scripts

--------------------------------

	When the vmlinux image is built, the linker script

	The kbuild infrastructure for `*lds` files is used in several

	architecture-specific files.

6.10 Generic header files

7.10 Generic header files

-------------------------

	The directory include/asm-generic contains the header files

	to list the file in the Kbuild file.

	See "7.2 generic-y" for further info on syntax etc.

6.11 Post-link pass

7.11 Post-link pass

-------------------

	If the file arch/xxx/Makefile.postlink exists, this makefile

	For example, powerpc uses this to check relocation sanity of

	the linked vmlinux file.

7 Kbuild syntax for exported headers

8 Kbuild syntax for exported headers

------------------------------------

The kernel includes a set of headers that is exported to userspace.

arch/<arch>/include/asm/ to list asm files coming from asm-generic.

See subsequent chapter for the syntax of the Kbuild file.

7.1 no-export-headers

8.1 no-export-headers

---------------------

	no-export-headers is essentially used by include/uapi/linux/Kbuild to

	avoid exporting specific headers (e.g. kvm.h) on architectures that do

	not support it. It should be avoided as much as possible.

7.2 generic-y

8.2 generic-y

-------------

	If an architecture uses a verbatim copy of a header from

			#include <asm-generic/termios.h>

7.3 generated-y

8.3 generated-y

---------------

	If an architecture generates other header files alongside generic-y

			#arch/x86/include/asm/Kbuild

			generated-y += syscalls_32.h

7.4 mandatory-y

8.4 mandatory-y

---------------

	mandatory-y is essentially used by include/(uapi/)asm-generic/Kbuild

	in arch/$(ARCH)/include/(uapi/)/asm, Kbuild will automatically generate

	a wrapper of the asm-generic one.

8 Kbuild Variables

9 Kbuild Variables

==================

The top Makefile exports the following variables:

	command.

9 Makefile language

===================

10 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

There are some cases where "=" is appropriate.  Usually, though, ":="

is the right choice.

10 Credits

11 Credits

==========

- Original version made by Michael Elizabeth Chastain, <mailto:mec@shout.net>

- Updates by Sam Ravnborg <sam@ravnborg.org>

- Language QA by Jan Engelhardt <jengelh@gmx.de>

11 TODO

12 TODO

=======

- Describe how kbuild supports shipped files with _shipped.

		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 add a top-level kbuild file,

		you can assign a space separated list

#

mainmenu "Linux/$(ARCH) $(KERNELVERSION) Kernel Configuration"

comment "Compiler: $(CC_VERSION_TEXT)"

source "scripts/Kconfig.include"

source "init/Kconfig"