linux/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)/
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)