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e732b538f4
In some modes of operation, Kbuild allows to build modules without having
vmlinux image around. In such case, generation of module BTF is impossible.
This patch changes the behavior to emit a warning about impossibility of
generating kernel module BTF, instead of breaking the build. This is especially
important for out-of-tree external module builds.
In vmlinux-less mode:
$ make clean
$ make modules_prepare
$ touch drivers/acpi/button.c
$ make M=drivers/acpi
...
CC [M] drivers/acpi/button.o
MODPOST drivers/acpi/Module.symvers
LD [M] drivers/acpi/button.ko
BTF [M] drivers/acpi/button.ko
Skipping BTF generation for drivers/acpi/button.ko due to unavailability of vmlinux
...
$ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1
... empty ...
Now with normal build:
$ make all
...
LD [M] drivers/acpi/button.ko
BTF [M] drivers/acpi/button.ko
...
$ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1
[60] .BTF PROGBITS 0000000000000000 00029310
000000000000ab3f 0000000000000000 0 0 1
Fixes: 5f9ae91f7c ("kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it")
Reported-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Link: https://lore.kernel.org/bpf/20201121070829.2612884-1-andrii@kernel.org
80 lines
2.7 KiB
Makefile
80 lines
2.7 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0-only
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# ===========================================================================
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# Module final link
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# ===========================================================================
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PHONY := __modfinal
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__modfinal:
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include include/config/auto.conf
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include $(srctree)/scripts/Kbuild.include
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# for c_flags
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include $(srctree)/scripts/Makefile.lib
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# find all modules listed in modules.order
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modules := $(sort $(shell cat $(MODORDER)))
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__modfinal: $(modules)
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@:
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# modname and part-of-module are set to make c_flags define proper module flags
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modname = $(notdir $(@:.mod.o=))
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part-of-module = y
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quiet_cmd_cc_o_c = CC [M] $@
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cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
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%.mod.o: %.mod.c FORCE
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$(call if_changed_dep,cc_o_c)
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ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
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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) \
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-T scripts/module.lds -o $@ $(filter %.o, $^); \
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$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
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quiet_cmd_btf_ko = BTF [M] $@
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cmd_btf_ko = \
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if [ -f vmlinux ]; then \
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LLVM_OBJCOPY=$(OBJCOPY) $(PAHOLE) -J --btf_base vmlinux $@; \
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else \
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printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \
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fi;
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# Same as newer-prereqs, but allows to exclude specified extra dependencies
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newer_prereqs_except = $(filter-out $(PHONY) $(1),$?)
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# Same as if_changed, but allows to exclude specified extra dependencies
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if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \
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$(cmd); \
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printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
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# Re-generate module BTFs if either module's .ko or vmlinux changed
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$(modules): %.ko: %.o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE
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+$(call if_changed_except,ld_ko_o,vmlinux)
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ifdef CONFIG_DEBUG_INFO_BTF_MODULES
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+$(if $(newer-prereqs),$(call cmd,btf_ko))
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endif
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targets += $(modules) $(modules:.ko=.mod.o)
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# Add FORCE to the prequisites of a target to force it to be always rebuilt.
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# ---------------------------------------------------------------------------
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PHONY += FORCE
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FORCE:
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# Read all saved command lines and dependencies for the $(targets) we
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# may be building above, using $(if_changed{,_dep}). As an
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# optimization, we don't need to read them if the target does not
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# exist, we will rebuild anyway in that case.
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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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