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![Sami Tolvanen](/assets/img/avatar_default.png)
With LTO, LLVM bitcode won't be compiled into native code until modpost_link, or modfinal for modules. This change postpones calls to objtool until after these steps, and moves objtool_args to Makefile.lib, so the arguments can be reused in Makefile.modfinal. As we didn't have objects to process earlier, we use --duplicate when processing vmlinux.o. This change also disables unreachable instruction warnings with LTO to avoid warnings about the int3 padding between functions. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org>
100 lines
3.2 KiB
Makefile
100 lines
3.2 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 and objtool_args
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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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ifdef CONFIG_LTO_CLANG
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# With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to
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# avoid a second slow LTO link
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prelink-ext := .lto
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# ELF processing was skipped earlier because we didn't have native code,
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# so let's now process the prelinked binary before we link the module.
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ifdef CONFIG_STACK_VALIDATION
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ifneq ($(SKIP_STACK_VALIDATION),1)
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cmd_ld_ko_o += \
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$(objtree)/tools/objtool/objtool $(objtool_args) \
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$(@:.ko=$(prelink-ext).o);
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endif # SKIP_STACK_VALIDATION
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endif # CONFIG_STACK_VALIDATION
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endif # CONFIG_LTO_CLANG
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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: %$(prelink-ext).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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