# ==========================================================================
  # Building
  # ==========================================================================
  
  src := $(obj)

  PHONY := __build

  __build:

  # Init all relevant variables used in kbuild files so
  # 1) they have correct type
  # 2) they do not inherit any value from the environment
  obj-y :=
  obj-m :=
  lib-y :=
  lib-m :=
  always :=
  targets :=
  subdir-y :=
  subdir-m :=
  EXTRA_AFLAGS   :=
  EXTRA_CFLAGS   :=
  EXTRA_CPPFLAGS :=
  EXTRA_LDFLAGS  :=

  asflags-y  :=
  ccflags-y  :=
  cppflags-y :=
  ldflags-y  :=

  subdir-asflags-y :=
  subdir-ccflags-y :=

  # Read auto.conf if it exists, otherwise ignore

  -include include/config/auto.conf

  include scripts/Kbuild.include

  # For backward compatibility check that these variables do not change

  save-cflags := $(CFLAGS)

  # The filename Kbuild has precedence over Makefile

  kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))

  kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
  include $(kbuild-file)
  
  # If the save-* variables changed error out
  ifeq ($(KBUILD_NOPEDANTIC),)
          ifneq ("$(save-cflags)","$(CFLAGS)")

                  $(error CFLAGS was changed in "$(kbuild-file)". Fix it to use ccflags-y)

          endif
  endif

  
  #

  # make W=... settings

  #

  # W=1 - warnings that may be relevant and does not occur too often
  # W=2 - warnings that occur quite often but may still be relevant
  # W=3 - the more obscure warnings, can most likely be ignored
  #
  # $(call cc-option, -W...) handles gcc -W.. options which

  # are not supported by all versions of the compiler
  ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS

  warning-  := $(empty)

  warning-1 := -Wextra -Wunused -Wno-unused-parameter
  warning-1 += -Wmissing-declarations
  warning-1 += -Wmissing-format-attribute
  warning-1 += -Wmissing-prototypes
  warning-1 += -Wold-style-definition
  warning-1 += $(call cc-option, -Wmissing-include-dirs)

  warning-1 += $(call cc-option, -Wunused-but-set-variable)

  
  warning-2 := -Waggregate-return
  warning-2 += -Wcast-align
  warning-2 += -Wdisabled-optimization
  warning-2 += -Wnested-externs
  warning-2 += -Wshadow
  warning-2 += $(call cc-option, -Wlogical-op)
  
  warning-3 := -Wbad-function-cast
  warning-3 += -Wcast-qual
  warning-3 += -Wconversion
  warning-3 += -Wpacked
  warning-3 += -Wpadded
  warning-3 += -Wpointer-arith
  warning-3 += -Wredundant-decls
  warning-3 += -Wswitch-default
  warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
  warning-3 += $(call cc-option, -Wvla)

  warning := $(warning-$(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
  warning += $(warning-$(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
  warning += $(warning-$(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))

  ifeq ("$(strip $(warning))","")

          $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
  endif
  
  KBUILD_CFLAGS += $(warning)

  endif

  include scripts/Makefile.lib
  
  ifdef host-progs
  ifneq ($(hostprogs-y),$(host-progs))
  $(warning kbuild: $(obj)/Makefile - Usage of host-progs is deprecated. Please replace with hostprogs-y!)
  hostprogs-y += $(host-progs)
  endif
  endif

  # Do not include host rules unless needed

  ifneq ($(hostprogs-y)$(hostprogs-m),)
  include scripts/Makefile.host
  endif
  
  ifneq ($(KBUILD_SRC),)
  # Create output directory if not already present
  _dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj))
  
  # Create directories for object files if directory does not exist
  # Needed when obj-y := dir/file.o syntax is used
  _dummy := $(foreach d,$(obj-dirs), $(shell [ -d $(d) ] || mkdir -p $(d)))
  endif

  ifndef obj
  $(warning kbuild: Makefile.build is included improperly)
  endif
  
  # ===========================================================================
  
  ifneq ($(strip $(lib-y) $(lib-m) $(lib-n) $(lib-)),)
  lib-target := $(obj)/lib.a
  endif

  ifneq ($(strip $(obj-y) $(obj-m) $(obj-n) $(obj-) $(subdir-m) $(lib-target)),)

  builtin-target := $(obj)/built-in.o
  endif

  modorder-target := $(obj)/modules.order

  # We keep a list of all modules in $(MODVERDIR)
  
  __build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \

  	 $(if $(KBUILD_MODULES),$(obj-m) $(modorder-target)) \

  	 $(subdir-ym) $(always)
  	@:
  
  # Linus' kernel sanity checking tool
  ifneq ($(KBUILD_CHECKSRC),0)
    ifeq ($(KBUILD_CHECKSRC),2)
      quiet_cmd_force_checksrc = CHECK   $<
            cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $< ;
    else
        quiet_cmd_checksrc     = CHECK   $<
              cmd_checksrc     = $(CHECK) $(CHECKFLAGS) $(c_flags) $< ;
    endif
  endif

  # Do section mismatch analysis for each module/built-in.o
  ifdef CONFIG_DEBUG_SECTION_MISMATCH
    cmd_secanalysis = ; scripts/mod/modpost $@
  endif

  
  # Compile C sources (.c)
  # ---------------------------------------------------------------------------
  
  # Default is built-in, unless we know otherwise

  modkern_cflags =                                          \
  	$(if $(part-of-module),                           \
  		$(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \

  		$(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL))

  quiet_modtag := $(empty)   $(empty)

  $(real-objs-m)        : part-of-module := y
  $(real-objs-m:.o=.i)  : part-of-module := y
  $(real-objs-m:.o=.s)  : part-of-module := y
  $(real-objs-m:.o=.lst): part-of-module := y

  
  $(real-objs-m)        : quiet_modtag := [M]
  $(real-objs-m:.o=.i)  : quiet_modtag := [M]
  $(real-objs-m:.o=.s)  : quiet_modtag := [M]
  $(real-objs-m:.o=.lst): quiet_modtag := [M]
  
  $(obj-m)              : quiet_modtag := [M]
  
  # Default for not multi-part modules

  modname = $(basetarget)

  
  $(multi-objs-m)         : modname = $(modname-multi)
  $(multi-objs-m:.o=.i)   : modname = $(modname-multi)
  $(multi-objs-m:.o=.s)   : modname = $(modname-multi)
  $(multi-objs-m:.o=.lst) : modname = $(modname-multi)
  $(multi-objs-y)         : modname = $(modname-multi)
  $(multi-objs-y:.o=.i)   : modname = $(modname-multi)
  $(multi-objs-y:.o=.s)   : modname = $(modname-multi)
  $(multi-objs-y:.o=.lst) : modname = $(modname-multi)
  
  quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@

  cmd_cc_s_c       = $(CC) $(c_flags) -fverbose-asm -S -o $@ $<

  $(obj)/%.s: $(src)/%.c FORCE

  	$(call if_changed_dep,cc_s_c)
  
  quiet_cmd_cc_i_c = CPP $(quiet_modtag) $@
  cmd_cc_i_c       = $(CPP) $(c_flags)   -o $@ $<

  $(obj)/%.i: $(src)/%.c FORCE

  	$(call if_changed_dep,cc_i_c)

  cmd_gensymtypes =                                                           \

      $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \

      $(GENKSYMS) $(if $(1), -T $(2)) -a $(ARCH)                              \

       $(if $(KBUILD_PRESERVE),-p)                                            \

       -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))

  quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@

  cmd_cc_symtypes_c =                                                         \
      set -e;                                                                 \

      $(call cmd_gensymtypes,true,$@) >/dev/null;                             \

      test -s $@ || rm -f $@

  $(obj)/%.symtypes : $(src)/%.c FORCE

  	$(call cmd,cc_symtypes_c)

  # C (.c) files
  # The C file is compiled and updated dependency information is generated.
  # (See cmd_cc_o_c + relevant part of rule_cc_o_c)
  
  quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
  
  ifndef CONFIG_MODVERSIONS
  cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
  
  else
  # When module versioning is enabled the following steps are executed:

  # o compile a .tmp_<file>.o from <file>.c
  # o if .tmp_<file>.o doesn't contain a __ksymtab version, i.e. does
  #   not export symbols, we just rename .tmp_<file>.o to <file>.o and

  #   are done.
  # o otherwise, we calculate symbol versions using the good old
  #   genksyms on the preprocessed source and postprocess them in a way

  #   that they are usable as a linker script
  # o generate <file>.o from .tmp_<file>.o using the linker to
  #   replace the unresolved symbols __crc_exported_symbol with
  #   the actual value of the checksum generated by genksyms

  cmd_cc_o_c = $(CC) $(c_flags) -c -o $(@D)/.tmp_$(@F) $<

  cmd_modversions =								\
  	if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then		\
  		$(call cmd_gensymtypes,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
  		    > $(@D)/.tmp_$(@F:.o=.ver);					\
  										\
  		$(LD) $(LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F) 			\
  			-T $(@D)/.tmp_$(@F:.o=.ver);				\
  		rm -f $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.ver);		\
  	else									\
  		mv -f $(@D)/.tmp_$(@F) $@;					\

  	fi;
  endif

  ifdef CONFIG_FTRACE_MCOUNT_RECORD

  ifdef BUILD_C_RECORDMCOUNT

  ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
    RECORDMCOUNT_FLAGS = -w
  endif

  # Due to recursion, we must skip empty.o.
  # The empty.o file is created in the make process in order to determine
  #  the target endianness and word size. It is made before all other C
  #  files, including recordmcount.

  sub_cmd_record_mcount =					\
  	if [ $(@) != "scripts/mod/empty.o" ]; then	\

  		$(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";	\

  	fi;

  recordmcount_source := $(srctree)/scripts/recordmcount.c \
  		    $(srctree)/scripts/recordmcount.h

  else

  sub_cmd_record_mcount = set -e ; perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \

  	"$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \

  	"$(if $(CONFIG_64BIT),64,32)" \

  	"$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CFLAGS)" \
  	"$(LD)" "$(NM)" "$(RM)" "$(MV)" \

  	"$(if $(part-of-module),1,0)" "$(@)";

  recordmcount_source := $(srctree)/scripts/recordmcount.pl

  endif

  cmd_record_mcount = 						\
  	if [ "$(findstring -pg,$(_c_flags))" = "-pg" ]; then	\
  		$(sub_cmd_record_mcount)			\
  	fi;

  endif

  define rule_cc_o_c

  	$(call echo-cmd,checksrc) $(cmd_checksrc)			  \
  	$(call echo-cmd,cc_o_c) $(cmd_cc_o_c);				  \

  	$(cmd_modversions)						  \

  	$(call echo-cmd,record_mcount)					  \

  	$(cmd_record_mcount)						  \

  	scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' >    \
  	                                              $(dot-target).tmp;  \

  	rm -f $(depfile);						  \

  	mv -f $(dot-target).tmp $(dot-target).cmd

  endef
  
  # Built-in and composite module parts

  $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE

  	$(call cmd,force_checksrc)
  	$(call if_changed_rule,cc_o_c)
  
  # Single-part modules are special since we need to mark them in $(MODVERDIR)

  $(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE

  	$(call cmd,force_checksrc)
  	$(call if_changed_rule,cc_o_c)
  	@{ echo $(@:.o=.ko); echo $@; } > $(MODVERDIR)/$(@F:.o=.mod)
  
  quiet_cmd_cc_lst_c = MKLST   $@
        cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
  		     $(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
  				     System.map $(OBJDUMP) > $@

  $(obj)/%.lst: $(src)/%.c FORCE

  	$(call if_changed_dep,cc_lst_c)
  
  # Compile assembler sources (.S)
  # ---------------------------------------------------------------------------

  modkern_aflags := $(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL)

  $(real-objs-m)      : modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
  $(real-objs-m:.o=.s): modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)

  
  quiet_cmd_as_s_S = CPP $(quiet_modtag) $@
  cmd_as_s_S       = $(CPP) $(a_flags)   -o $@ $< 

  $(obj)/%.s: $(src)/%.S FORCE

  	$(call if_changed_dep,as_s_S)
  
  quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
  cmd_as_o_S       = $(CC) $(a_flags) -c -o $@ $<

  $(obj)/%.o: $(src)/%.S FORCE

  	$(call if_changed_dep,as_o_S)
  
  targets += $(real-objs-y) $(real-objs-m) $(lib-y)
  targets += $(extra-y) $(MAKECMDGOALS) $(always)
  
  # Linker scripts preprocessor (.lds.S -> .lds)
  # ---------------------------------------------------------------------------
  quiet_cmd_cpp_lds_S = LDS     $@

        cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -C -U$(ARCH) \

  	                     -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<

  $(obj)/%.lds: $(src)/%.lds.S FORCE

  	$(call if_changed_dep,cpp_lds_S)
  
  # Build the compiled-in targets
  # ---------------------------------------------------------------------------
  
  # To build objects in subdirs, we need to descend into the directories
  $(sort $(subdir-obj-y)): $(subdir-ym) ;
  
  #
  # Rule to compile a set of .o files into one .o file
  #
  ifdef builtin-target
  quiet_cmd_link_o_target = LD      $@
  # If the list of objects to link is empty, just create an empty built-in.o
  cmd_link_o_target = $(if $(strip $(obj-y)),\

  		      $(LD) $(ld_flags) -r -o $@ $(filter $(obj-y), $^) \
  		      $(cmd_secanalysis),\

  		      rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS) $@)

  
  $(builtin-target): $(obj-y) FORCE
  	$(call if_changed,link_o_target)
  
  targets += $(builtin-target)
  endif # builtin-target
  
  #

  # Rule to create modules.order file
  #
  # Create commands to either record .ko file or cat modules.order from
  # a subdirectory
  modorder-cmds =						\
  	$(foreach m, $(modorder),			\
  		$(if $(filter %/modules.order, $m),	\
  			cat $m;, echo kernel/$m;))
  
  $(modorder-target): $(subdir-ym) FORCE
  	$(Q)(cat /dev/null; $(modorder-cmds)) > $@
  
  #

  # Rule to compile a set of .o files into one .a file
  #
  ifdef lib-target
  quiet_cmd_link_l_target = AR      $@

  cmd_link_l_target = rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS) $@ $(lib-y)

  
  $(lib-target): $(lib-y) FORCE
  	$(call if_changed,link_l_target)
  
  targets += $(lib-target)
  endif
  
  #
  # Rule to link composite objects
  #
  #  Composite objects are specified in kbuild makefile as follows:
  #    <composite-object>-objs := <list of .o files>
  #  or
  #    <composite-object>-y    := <list of .o files>
  link_multi_deps =                     \
  $(filter $(addprefix $(obj)/,         \
  $($(subst $(obj)/,,$(@:.o=-objs)))    \
  $($(subst $(obj)/,,$(@:.o=-y)))), $^)
   
  quiet_cmd_link_multi-y = LD      $@

  cmd_link_multi-y = $(LD) $(ld_flags) -r -o $@ $(link_multi_deps) $(cmd_secanalysis)

  
  quiet_cmd_link_multi-m = LD [M]  $@

  cmd_link_multi-m = $(cmd_link_multi-y)

  
  # We would rather have a list of rules like
  # 	foo.o: $(foo-objs)
  # but that's not so easy, so we rather make all composite objects depend
  # on the set of all their parts
  $(multi-used-y) : %.o: $(multi-objs-y) FORCE
  	$(call if_changed,link_multi-y)
  
  $(multi-used-m) : %.o: $(multi-objs-m) FORCE
  	$(call if_changed,link_multi-m)
  	@{ echo $(@:.o=.ko); echo $(link_multi_deps); } > $(MODVERDIR)/$(@F:.o=.mod)
  
  targets += $(multi-used-y) $(multi-used-m)
  
  
  # Descending
  # ---------------------------------------------------------------------------

  PHONY += $(subdir-ym)

  $(subdir-ym):
  	$(Q)$(MAKE) $(build)=$@
  
  # Add FORCE to the prequisites of a target to force it to be always rebuilt.
  # ---------------------------------------------------------------------------

  PHONY += FORCE

  
  FORCE:
  
  # Read all saved command lines and dependencies for the $(targets) we
  # may be building above, using $(if_changed{,_dep}). As an
  # optimization, we don't need to read them if the target does not
  # exist, we will rebuild anyway in that case.
  
  targets := $(wildcard $(sort $(targets)))
  cmd_files := $(wildcard $(foreach f,$(targets),$(dir $(f)).$(notdir $(f)).cmd))
  
  ifneq ($(cmd_files),)
    include $(cmd_files)
  endif

  # Declare the contents of the .PHONY variable as phony.  We keep that
  # information in a variable se we can use it in if_changed and friends.
  
  .PHONY: $(PHONY)