FreeBSD/Linux Kernel Cross Reference
sys/scripts/Makefile.modpost

     # ===========================================================================
     # 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)/
    __modules := $(sort $(shell grep -h '\.ko$$' /dev/null $(wildcard $(MODVERDIR)/*.mod)))
    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))
    
    ifneq ($(KBUILD_BUILDHOST),$(ARCH))
            cross_build := 1
    endif
    
    # 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) \
     $(if $(cross_build),-c)
    
    quiet_cmd_modpost = MODPOST $(words $(filter-out vmlinux FORCE, $^)) modules
          cmd_modpost = $(modpost) -s
    
    PHONY += __modpost
    __modpost: $(modules:.ko=.o) FORCE
            $(call cmd,modpost) $(wildcard vmlinux) $(filter-out FORCE,$^)
    
    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)

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