# ==========================================================================
  # 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  :=

  # Read .config if it exist, otherwise ignore

  -include include/config/auto.conf

  include scripts/Kbuild.include

  # The filename Kbuild has precedence over Makefile

  kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
  include $(if $(wildcard $(kbuild-dir)/Kbuild), $(kbuild-dir)/Kbuild, $(kbuild-dir)/Makefile)

  
  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 unles 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
  
  
  ifdef EXTRA_TARGETS
  $(warning kbuild: $(obj)/Makefile - Usage of EXTRA_TARGETS is obsolete in 2.6. Please fix!)
  endif
  
  ifdef build-targets
  $(warning kbuild: $(obj)/Makefile - Usage of build-targets is obsolete in 2.6. Please fix!)
  endif
  
  ifdef export-objs
  $(warning kbuild: $(obj)/Makefile - Usage of export-objs is obsolete in 2.6. Please fix!)
  endif
  
  ifdef O_TARGET
  $(warning kbuild: $(obj)/Makefile - Usage of O_TARGET := $(O_TARGET) is obsolete in 2.6. Please fix!)
  endif
  
  ifdef L_TARGET
  $(error kbuild: $(obj)/Makefile - Use of L_TARGET is replaced by lib-y in 2.6. Please fix!)
  endif
  
  ifdef list-multi
  $(warning kbuild: $(obj)/Makefile - list-multi := $(list-multi) is obsolete in 2.6. Please fix!)
  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-) $(lib-target)),)
  builtin-target := $(obj)/built-in.o
  endif
  
  # We keep a list of all modules in $(MODVERDIR)
  
  __build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \
  	 $(if $(KBUILD_MODULES),$(obj-m)) \
  	 $(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
  
  
  # Compile C sources (.c)
  # ---------------------------------------------------------------------------
  
  # Default is built-in, unless we know otherwise
  modkern_cflags := $(CFLAGS_KERNEL)
  quiet_modtag := $(empty)   $(empty)
  
  $(real-objs-m)        : modkern_cflags := $(CFLAGS_MODULE)
  $(real-objs-m:.o=.i)  : modkern_cflags := $(CFLAGS_MODULE)
  $(real-objs-m:.o=.s)  : modkern_cflags := $(CFLAGS_MODULE)
  $(real-objs-m:.o=.lst): modkern_cflags := $(CFLAGS_MODULE)
  
  $(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)

  quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
  cmd_cc_symtypes_c	   = \
  		$(CPP) -D__GENKSYMS__ $(c_flags) $<			\
  		| $(GENKSYMS) -T $@ >/dev/null;				\
  		test -s $@ || rm -f $@

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

  	$(call if_changed_dep,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	\
  		$(CPP) -D__GENKSYMS__ $(c_flags) $<			\

  		| $(GENKSYMS) $(if $(KBUILD_SYMTYPES),			\
  			      -T $(@D)/$(@F:.o=.symtypes)) -a $(ARCH)	\

  		> $(@D)/.tmp_$(@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
  
  define rule_cc_o_c

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

  	$(cmd_modversions)						  \

  	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 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 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 := $(AFLAGS_KERNEL)
  
  $(real-objs-m)      : modkern_aflags := $(AFLAGS_MODULE)
  $(real-objs-m:.o=.s): modkern_aflags := $(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) -D__ASSEMBLY__ -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), $^),\
  		      rm -f $@; $(AR) rcs $@)
  
  $(builtin-target): $(obj-y) FORCE
  	$(call if_changed,link_o_target)
  
  targets += $(builtin-target)
  endif # builtin-target
  
  #
  # 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) $(EXTRA_ARFLAGS) rcs $@ $(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)
  
  quiet_cmd_link_multi-m = LD [M]  $@
  cmd_link_multi-m = $(LD) $(ld_flags) $(LDFLAGS_MODULE) -o $@ $(link_multi_deps)
  
  # 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)