13b25489b6
Currently, Kbuild always operates in the output directory of the kernel,
even when building external modules. This increases the risk of external
module Makefiles attempting to write to the kernel directory.
This commit switches the working directory to the external module
directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
some build artifacts.
The command for building external modules maintains backward
compatibility, but Makefiles that rely on working in the kernel
directory may break. In such cases, $(objtree) and $(srctree) should
be used to refer to the output and source directories of the kernel.
The appearance of the build log will change as follows:
[Before]
$ make -C /path/to/my/linux M=/path/to/my/externel/module
make: Entering directory '/path/to/my/linux'
CC [M] /path/to/my/externel/module/helloworld.o
MODPOST /path/to/my/externel/module/Module.symvers
CC [M] /path/to/my/externel/module/helloworld.mod.o
CC [M] /path/to/my/externel/module/.module-common.o
LD [M] /path/to/my/externel/module/helloworld.ko
make: Leaving directory '/path/to/my/linux'
[After]
$ make -C /path/to/my/linux M=/path/to/my/externel/module
make: Entering directory '/path/to/my/linux'
make[1]: Entering directory '/path/to/my/externel/module'
CC [M] helloworld.o
MODPOST Module.symvers
CC [M] helloworld.mod.o
CC [M] .module-common.o
LD [M] helloworld.ko
make[1]: Leaving directory '/path/to/my/externel/module'
make: Leaving directory '/path/to/my/linux'
Printing "Entering directory" twice is cumbersome. This will be
addressed later.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
155 lines
4.8 KiB
Text
155 lines
4.8 KiB
Text
# SPDX-License-Identifier: GPL-2.0
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# ===========================================================================
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# Module versions
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# ===========================================================================
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#
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# Stage one of module building created the following:
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# 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, listing the name of the preliminary <module>.o file,
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# plus all .o files
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# d) modules.order, which lists all the modules
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# Stage 2 is handled by this file and does the following
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# 1) Find all modules listed in modules.order
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# 2) modpost is then used to
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# 3) create one <module>.mod.c file per module
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# 4) create one Module.symvers file with CRC for all exported symbols
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# Step 3 is used to place certain information in the module's ELF
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# 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
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# - SMP is CONFIG_SMP
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# - PREEMPT is CONFIG_PREEMPT[_RT]
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# - GCC Version
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# Module info
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# - Module version (MODULE_VERSION)
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# - Module alias'es (MODULE_ALIAS)
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# - Module license (MODULE_LICENSE)
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# - See include/linux/module.h for more details
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# 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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PHONY := __modpost
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__modpost:
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include $(objtree)/include/config/auto.conf
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include $(srctree)/scripts/Kbuild.include
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MODPOST = $(objtree)/scripts/mod/modpost
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modpost-args = \
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$(if $(CONFIG_MODULES),-M) \
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$(if $(CONFIG_MODVERSIONS),-m) \
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$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \
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$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E) \
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$(if $(KBUILD_MODPOST_WARN),-w) \
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$(if $(KBUILD_NSDEPS),-d $(MODULES_NSDEPS)) \
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$(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N) \
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$(if $(findstring 1, $(KBUILD_EXTRA_WARN)),-W) \
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-o $@
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modpost-deps := $(MODPOST)
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# 'make -i -k' ignores compile errors, and builds as many modules as possible.
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ifneq ($(findstring i,$(filter-out --%,$(MAKEFLAGS))),)
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modpost-args += -n
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endif
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# Read out modules.order to pass in modpost.
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# Otherwise, allmodconfig would fail with "Argument list too long".
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ifdef KBUILD_MODULES
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modpost-args += -T $(MODORDER)
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modpost-deps += $(MODORDER)
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endif
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ifeq ($(KBUILD_EXTMOD),)
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# Generate the list of in-tree objects in vmlinux
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# ---------------------------------------------------------------------------
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# This is used to retrieve symbol versions generated by genksyms.
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ifdef CONFIG_MODVERSIONS
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vmlinux.symvers Module.symvers: .vmlinux.objs
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endif
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# Ignore libgcc.a
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# Some architectures do '$(CC) --print-libgcc-file-name' to borrow libgcc.a
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# from the toolchain, but there is no EXPORT_SYMBOL in it.
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quiet_cmd_vmlinux_objs = GEN $@
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cmd_vmlinux_objs = \
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for f in $(real-prereqs); do \
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case $${f} in \
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*libgcc.a) ;; \
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*) $(AR) t $${f} ;; \
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esac \
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done > $@
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targets += .vmlinux.objs
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.vmlinux.objs: vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE
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$(call if_changed,vmlinux_objs)
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ifdef CONFIG_TRIM_UNUSED_KSYMS
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ksym-wl := $(CONFIG_UNUSED_KSYMS_WHITELIST)
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ksym-wl := $(if $(filter-out /%, $(ksym-wl)),$(if $(wildcard $(ksym-wl)),,$(srctree)/))$(ksym-wl)
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modpost-args += -t $(addprefix -u , $(ksym-wl))
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modpost-deps += $(ksym-wl)
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endif
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ifeq ($(wildcard vmlinux.o),)
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missing-input := vmlinux.o
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output-symdump := modules-only.symvers
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else
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modpost-args += vmlinux.o
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modpost-deps += vmlinux.o
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output-symdump := $(if $(KBUILD_MODULES), Module.symvers, vmlinux.symvers)
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endif
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else
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# set src + obj - they may be used in the modules's Makefile
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obj := .
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src := $(srcroot)
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# Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
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include $(kbuild-file)
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output-symdump := Module.symvers
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ifeq ($(wildcard $(objtree)/Module.symvers),)
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missing-input := $(objtree)/Module.symvers
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else
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modpost-args += -i $(objtree)/Module.symvers
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modpost-deps += $(objtree)/Module.symvers
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endif
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modpost-args += -e $(addprefix -i , $(KBUILD_EXTRA_SYMBOLS))
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endif # ($(KBUILD_EXTMOD),)
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quiet_cmd_modpost = MODPOST $@
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cmd_modpost = \
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$(if $(missing-input), \
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echo >&2 "WARNING: $(missing-input) is missing."; \
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echo >&2 " Modules may not have dependencies or modversions."; \
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echo >&2 " You may get many unresolved symbol errors."; \
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echo >&2 " You can set KBUILD_MODPOST_WARN=1 to turn errors into warning"; \
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echo >&2 " if you want to proceed at your own risk.";) \
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$(MODPOST) $(modpost-args)
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targets += $(output-symdump)
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$(output-symdump): $(modpost-deps) FORCE
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$(call if_changed,modpost)
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__modpost: $(output-symdump)
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PHONY += FORCE
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FORCE:
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existing-targets := $(wildcard $(sort $(targets)))
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-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
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.PHONY: $(PHONY)
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