Makefile.modpost

# SPDX-License-Identifier: GPL-2.0
# ===========================================================================
# 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, listing the name of the preliminary <module>.o file,
#    plus all .o files
# d) modules.order, which lists all the modules

# Stage 2 is handled by this file and does the following
# 1) Find all modules listed in modules.order
# 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

# 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[_RT]
#     - 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_NOFINAL can be set to skip the final link of modules.
# This is solely useful to speed up test compiles

PHONY := __modpost
__modpost:

include include/config/auto.conf
include $(srctree)/scripts/Kbuild.include

# for ld_flags
include $(srctree)/scripts/Makefile.lib

MODPOST = scripts/mod/modpost								\
	$(if $(CONFIG_MODVERSIONS),-m)							\
	$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a)					\
	$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)					\
	-o $@

ifdef MODPOST_VMLINUX

quiet_cmd_modpost = MODPOST $@
      cmd_modpost = $(MODPOST) $<

vmlinux.symvers: vmlinux.o
	$(call cmd,modpost)

__modpost: vmlinux.symvers

else

ifeq ($(KBUILD_EXTMOD),)

input-symdump := vmlinux.symvers
output-symdump := modules-only.symvers

quiet_cmd_cat = GEN     $@
      cmd_cat = cat $(real-prereqs) > $@

ifneq ($(wildcard vmlinux.symvers),)

__modpost: Module.symvers
Module.symvers: vmlinux.symvers modules-only.symvers FORCE
	$(call if_changed,cat)

targets += Module.symvers

endif

else

# set src + obj - they may be used in the modules's Makefile
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)

# modpost option for external modules
MODPOST += -e

input-symdump := Module.symvers $(KBUILD_EXTRA_SYMBOLS)
output-symdump := $(KBUILD_EXTMOD)/Module.symvers

endif

existing-input-symdump := $(wildcard $(input-symdump))

# modpost options for modules (both in-kernel and external)
MODPOST += \
	$(addprefix -i ,$(existing-input-symdump)) \
	$(if $(KBUILD_NSDEPS),-d $(MODULES_NSDEPS)) \
	$(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N)

# 'make -i -k' ignores compile errors, and builds as many modules as possible.
ifneq ($(findstring i,$(filter-out --%,$(MAKEFLAGS))),)
MODPOST += -n
endif

# Clear VPATH to not search for *.symvers in $(srctree). Check only $(objtree).
VPATH :=
$(input-symdump):
	@echo >&2 'WARNING: Symbol version dump "$@" is missing.'
	@echo >&2 '         Modules may not have dependencies or modversions.'
	@echo >&2 '         You may get many unresolved symbol warnings.'

ifdef CONFIG_LTO_CLANG
# With CONFIG_LTO_CLANG, .o files might be LLVM bitcode, so we need to run
# LTO to compile them into native code before running modpost
prelink-ext := .lto

quiet_cmd_cc_lto_link_modules = LTO [M] $@
cmd_cc_lto_link_modules =						\
	$(LD) $(ld_flags) -r -o $@					\
		$(shell [ -s $(@:.lto.o=.o.symversions) ] &&		\
			echo -T $(@:.lto.o=.o.symversions))		\
		--whole-archive $^

%.lto.o: %.o
	$(call if_changed,cc_lto_link_modules)
endif

modules := $(sort $(shell cat $(MODORDER)))

# KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined symbols
ifneq ($(KBUILD_MODPOST_WARN)$(filter-out $(existing-input-symdump), $(input-symdump)),)
MODPOST += -w
endif

# Read out modules.order to pass in modpost.
# Otherwise, allmodconfig would fail with "Argument list too long".
quiet_cmd_modpost = MODPOST $@
      cmd_modpost = sed 's/\.ko$$/$(prelink-ext)\.o/' $< | $(MODPOST) -T -

$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(prelink-ext).o) FORCE
	$(call if_changed,modpost)

targets += $(output-symdump)

__modpost: $(output-symdump)
ifneq ($(KBUILD_MODPOST_NOFINAL),1)
	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modfinal
endif

PHONY += FORCE
FORCE:

existing-targets := $(wildcard $(sort $(targets)))

-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)

endif

.PHONY: $(PHONY)