Makefile.modpost 5.35 KB
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# SPDX-License-Identifier: GPL-2.0
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# ===========================================================================
# Module versions
# ===========================================================================
#
# Stage one of module building created the following:
# a) The individual .o files used for the module
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# b) A <module>.o file which is the .o files above linked together
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# 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
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# 6) final link of the module to a <module.ko> file
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# Step 3 is used to place certain information in the module's ELF
# section, including information such as:
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#   Version magic (see include/linux/vermagic.h for full details)
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#     - 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,
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# where the CRC of each module is retrieved from the Module.symvers file.
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# 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.
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# This is solely useful to speed up test compiles
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PHONY := _modpost
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_modpost: __modpost

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include include/config/auto.conf
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include scripts/Kbuild.include
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# When building external modules load the Kbuild file to retrieve EXTRA_SYMBOLS info
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ifneq ($(KBUILD_EXTMOD),)
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# set src + obj - they may be used when building the .mod.c file
obj := $(KBUILD_EXTMOD)
src := $(obj)

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# Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
include $(if $(wildcard $(KBUILD_EXTMOD)/Kbuild), \
             $(KBUILD_EXTMOD)/Kbuild, $(KBUILD_EXTMOD)/Makefile)
endif

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include scripts/Makefile.lib

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kernelsymfile := $(objtree)/Module.symvers
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modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
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# Step 1), find all modules listed in $(MODVERDIR)/
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MODLISTCMD := find $(MODVERDIR) -name '*.mod' | xargs -r grep -h '\.ko$$' | sort -u
__modules := $(shell $(MODLISTCMD))
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modules   := $(patsubst %.o,%.ko, $(wildcard $(__modules:.ko=.o)))

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# Stop after building .o files if NOFINAL is set. Makes compile tests quicker
_modpost: $(if $(KBUILD_MODPOST_NOFINAL), $(modules:.ko:.o),$(modules))
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# Step 2), invoke modpost
#  Includes step 3,4
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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))      \
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 $(if $(KBUILD_EXTRA_SYMBOLS), $(patsubst %, -e %,$(KBUILD_EXTRA_SYMBOLS))) \
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 $(if $(KBUILD_EXTMOD),-o $(modulesymfile))      \
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 $(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S)      \
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 $(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)  \
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 $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w)
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MODPOST_OPT=$(subst -i,-n,$(filter -i,$(MAKEFLAGS)))

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# We can go over command line length here, so be careful.
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quiet_cmd_modpost = MODPOST $(words $(filter-out vmlinux FORCE, $^)) modules
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      cmd_modpost = $(MODLISTCMD) | sed 's/\.ko$$/.o/' | $(modpost) $(MODPOST_OPT) -s -T -
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PHONY += __modpost
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__modpost: $(modules:.ko=.o) FORCE
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	$(call cmd,modpost) $(wildcard vmlinux)
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quiet_cmd_kernel-mod = MODPOST $@
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      cmd_kernel-mod = $(modpost) $@
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vmlinux.o: FORCE
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	$(call cmd,kernel-mod)

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# Declare generated files as targets for modpost
$(modules:.ko=.mod.c): __modpost ;


# Step 5), compile all *.mod.c files

# modname is set to make c_flags define KBUILD_MODNAME
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modname = $(notdir $(@:.mod.o=))
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quiet_cmd_cc_o_c = CC      $@
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      cmd_cc_o_c = $(CC) $(c_flags) $(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE) \
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		   -c -o $@ $<

$(modules:.ko=.mod.o): %.mod.o: %.mod.c FORCE
	$(call if_changed_dep,cc_o_c)

targets += $(modules:.ko=.mod.o)

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ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)

# Step 6), final link of the modules with optional arch pass after final link
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quiet_cmd_ld_ko_o = LD [M]  $@
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      cmd_ld_ko_o =                                                     \
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	$(LD) -r $(KBUILD_LDFLAGS)                                      \
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                 $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE)             \
                 -o $@ $(filter-out FORCE,$^) ;                         \
	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
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$(modules): %.ko :%.o %.mod.o FORCE
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	+$(call if_changed,ld_ko_o)
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targets += $(modules)


# Add FORCE to the prequisites of a target to force it to be always rebuilt.
# ---------------------------------------------------------------------------

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PHONY += FORCE
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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.

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cmd_files := $(wildcard $(foreach f,$(sort $(targets)),$(dir $(f)).$(notdir $(f)).cmd))
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ifneq ($(cmd_files),)
  include $(cmd_files)
endif
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.PHONY: $(PHONY)