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kbuild: detect objtool update without using .SECONDEXPANSION 

Redo commit 8852c55240 ("kbuild: Fix objtool dependency for
'OBJECT_FILES_NON_STANDARD_<obj> := n'") to add the objtool
dependency in a cleaner way.

Using .SECONDEXPANSION ends up with unreadable code due to escaped
dollars. Also, it is not efficient because the second half of
Makefile.build is parsed twice every time.

Append the objtool dependency to the *.cmd files at the build time.

This is what fixdep and gen_ksymdeps.sh already do. So, following the
same pattern seems a natural solution.

This allows us to drop $$(objtool_dep) entirely.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
This commit is contained in:
Masahiro Yamada 2021-08-31 16:39:56 +09:00
parent 918a6b7f68
commit ef62588c2c
1 changed files with 5 additions and 7 deletions
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12
scripts/Makefile.build
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@ -246,14 +246,11 @@ objtool-enabled = $(if $(filter-out y%, \
$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
objtool_obj = $(if $(objtool-enabled), $(objtool))
cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
endif # CONFIG_LTO_CLANG
endif # CONFIG_STACK_VALIDATION
# Rebuild all objects when objtool changes
objtool_dep = $(objtool_obj)
ifdef CONFIG_TRIM_UNUSED_KSYMS
cmd_gen_ksymdeps = \
$(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
@ -267,6 +264,7 @@ define rule_cc_o_c
$(call cmd,gen_ksymdeps)
$(call cmd,checksrc)
$(call cmd,checkdoc)
$(call cmd,gen_objtooldep)
$(call cmd,modversions_c)
$(call cmd,record_mcount)
endef
@ -274,12 +272,12 @@ endef
define rule_as_o_S
$(call cmd_and_fixdep,as_o_S)
$(call cmd,gen_ksymdeps)
$(call cmd,gen_objtooldep)
$(call cmd,modversions_S)
endef
# Built-in and composite module parts
.SECONDEXPANSION:
$(obj)/%.o: $(src)/%.c $(recordmcount_source) $$(objtool_dep) FORCE
$(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
$(call if_changed_rule,cc_o_c)
$(call cmd,force_checksrc)
@ -380,7 +378,7 @@ cmd_modversions_S = \
fi
endif
$(obj)/%.o: $(src)/%.S $$(objtool_dep) FORCE
$(obj)/%.o: $(src)/%.S FORCE
$(call if_changed_rule,as_o_S)
targets += $(filter-out $(subdir-builtin), $(real-obj-y))