# ===========================================================================
  # Module versions
  # ===========================================================================
  #
  # Stage one of module building created the following:
  # a) The individual .o files used for the module
  # b) A <module>.o file which is the .o files above linked together
  # c) A <module>.mod file in $(MODVERDIR)/, listing the name of the
  #    the preliminary <module>.o file, plus all .o files
  
  # Stage 2 is handled by this file and does the following
  # 1) Find all modules from the files listed in $(MODVERDIR)/
  # 2) modpost is then used to
  # 3)  create one <module>.mod.c file pr. module
  # 4)  create one Module.symvers file with CRC for all exported symbols
  # 5) compile all <module>.mod.c files
  # 6) final link of the module to a <module.ko> file
  
  # Step 3 is used to place certain information in the module's ELF
  # section, including information such as:
  #   Version magic (see include/linux/vermagic.h for full details)
  #     - Kernel release
  #     - SMP is CONFIG_SMP
  #     - PREEMPT is CONFIG_PREEMPT
  #     - GCC Version
  #   Module info
  #     - Module version (MODULE_VERSION)
  #     - Module alias'es (MODULE_ALIAS)
  #     - Module license (MODULE_LICENSE)
  #     - See include/linux/module.h for more details
  
  # Step 4 is solely used to allow module versioning in external modules,
  # where the CRC of each module is retrieved from the Module.symvers file.
  
  # KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined
  # symbols in the final module linking stage
  # KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
  # This is solely useful to speed up test compiles
  PHONY := _modpost
  _modpost: __modpost
  
  include include/config/auto.conf
  include scripts/Kbuild.include
  
  # When building external modules load the Kbuild file to retrieve EXTRA_SYMBOLS info
  ifneq ($(KBUILD_EXTMOD),)
  
  # set src + obj - they may be used when building the .mod.c file
  obj := $(KBUILD_EXTMOD)
  src := $(obj)
  
  # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
  include $(if $(wildcard $(KBUILD_EXTMOD)/Kbuild), \
               $(KBUILD_EXTMOD)/Kbuild, $(KBUILD_EXTMOD)/Makefile)
  endif
  
  include scripts/Makefile.lib
  
  kernelsymfile := $(objtree)/Module.symvers
  modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
  
  # Step 1), find all modules listed in $(MODVERDIR)/
  MODLISTCMD := find $(MODVERDIR) -name '*.mod' | xargs -r grep -h '\.ko$$' | sort -u
  __modules := $(shell $(MODLISTCMD))
  modules   := $(patsubst %.o,%.ko, $(wildcard $(__modules:.ko=.o)))
  
  # Stop after building .o files if NOFINAL is set. Makes compile tests quicker
  _modpost: $(if $(KBUILD_MODPOST_NOFINAL), $(modules:.ko:.o),$(modules))
  
  # Step 2), invoke modpost
  #  Includes step 3,4
  modpost = scripts/mod/modpost                    \
   $(if $(CONFIG_MODVERSIONS),-m)                  \
   $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a,)       \
   $(if $(KBUILD_EXTMOD),-i,-o) $(kernelsymfile)   \
   $(if $(KBUILD_EXTMOD),-I $(modulesymfile))      \
   $(if $(KBUILD_EXTRA_SYMBOLS), $(patsubst %, -e %,$(KBUILD_EXTRA_SYMBOLS))) \
   $(if $(KBUILD_EXTMOD),-o $(modulesymfile))      \
   $(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S)      \
   $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w)
  
  MODPOST_OPT=$(subst -i,-n,$(filter -i,$(MAKEFLAGS)))
  
  # We can go over command line length here, so be careful.
  quiet_cmd_modpost = MODPOST $(words $(filter-out vmlinux FORCE, $^)) modules
        cmd_modpost = $(MODLISTCMD) | sed 's/\.ko$$/.o/' | $(modpost) $(MODPOST_OPT) -s -T -
  
  PHONY += __modpost
  __modpost: $(modules:.ko=.o) FORCE
  	$(call cmd,modpost) $(wildcard vmlinux)
  
  quiet_cmd_kernel-mod = MODPOST $@
        cmd_kernel-mod = $(modpost) $@
  
  vmlinux.o: FORCE
  	$(call cmd,kernel-mod)
  
  # Declare generated files as targets for modpost
  $(symverfile):         __modpost ;
  $(modules:.ko=.mod.c): __modpost ;
  
  
  # Step 5), compile all *.mod.c files
  
  # modname is set to make c_flags define KBUILD_MODNAME
  modname = $(notdir $(@:.mod.o=))
  
  quiet_cmd_cc_o_c = CC      $@
        cmd_cc_o_c = $(CC) $(c_flags) $(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE) \
  		   -c -o $@ $<
  
  $(modules:.ko=.mod.o): %.mod.o: %.mod.c FORCE
  	$(call if_changed_dep,cc_o_c)
  
  targets += $(modules:.ko=.mod.o)
  
  # Step 6), final link of the modules
  quiet_cmd_ld_ko_o = LD [M]  $@
        cmd_ld_ko_o = $(LD) -r $(LDFLAGS)                                 \
                               $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
                               -o $@ $(filter-out FORCE,$^)
  
  $(modules): %.ko :%.o %.mod.o FORCE
  	$(call if_changed,ld_ko_o)
  
  targets += $(modules)
  
  
  # 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)