[PATCH 03/13] kbuild: detect objtool changes correctly and remove .SECONDEXPANSION

Masahiro Yamada
2021-08-19T00:58:22Z

This reverts commit 8852c5524029 ("kbuild: Fix objtool dependency for
'OBJECT_FILES_NON_STANDARD_<obj> := n'"), and fix the dependency in a
cleaner way.

Using .SECONDEXPANSION is expensive since Makefile.build is parsed
twice every time, and the escaping dollars makes the code unreadable.

Adding include/config/* as dependency is not maintainable either because
objtool_args is dependent on more CONFIG options.

A better fix is to include the objtool command in *.cmd files so any
command change is naturally detected by if_change.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

scripts/Makefile.build | 28 ++++++++++------------------
1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 31154e44c251..3e4cd1439cd4 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -155,7 +155,7 @@ $(obj)/%.ll: $(src)/%.c FORCE
# (See cmd_cc_o_c + relevant part of rule_cc_o_c)

quiet_cmd_cc_o_c = CC $(quiet_modtag) $@
- cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
+ cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $< $(cmd_objtool)

ifdef CONFIG_MODVERSIONS
# When module versioning is enabled the following steps are executed:
@@ -223,6 +223,8 @@ endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT

ifdef CONFIG_STACK_VALIDATION

+objtool := $(objtree)/tools/objtool/objtool
+
# Objtool arguments are also needed for modfinal with LTO, so we define
# then here to avoid duplication.
objtool_args = \
@@ -237,26 +239,19 @@ objtool_args = \

ifndef CONFIG_LTO_CLANG

-__objtool_obj := $(objtree)/tools/objtool/objtool
-
# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
# 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
cmd_objtool = $(if $(patsubst y%,, \
$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
- $(__objtool_obj) $(objtool_args) $@)
-objtool_obj = $(if $(patsubst y%,, \
- $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
- $(__objtool_obj))
+ ; $(objtool) $(objtool_args) $@)
+
+# Rebuild all objects when objtool is updated
+objtool_dep = $(objtool)

endif # CONFIG_LTO_CLANG
endif # CONFIG_STACK_VALIDATION

-# Rebuild all objects when objtool changes, or is enabled/disabled.
-objtool_dep = $(objtool_obj) \
- $(wildcard include/config/ORC_UNWINDER \
- include/config/STACK_VALIDATION)
-
ifdef CONFIG_TRIM_UNUSED_KSYMS
cmd_gen_ksymdeps = \
$(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
@@ -270,7 +265,6 @@ define rule_cc_o_c
$(call cmd,gen_ksymdeps)
$(call cmd,checksrc)
$(call cmd,checkdoc)
- $(call cmd,objtool)
$(call cmd,modversions_c)
$(call cmd,record_mcount)
endef
@@ -278,13 +272,11 @@ endef
define rule_as_o_S
$(call cmd_and_fixdep,as_o_S)
$(call cmd,gen_ksymdeps)
- $(call cmd,objtool)
$(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) $(objtool_dep) FORCE
$(call if_changed_rule,cc_o_c)
$(call cmd,force_checksrc)

@@ -367,7 +359,7 @@ $(obj)/%.s: $(src)/%.S FORCE
$(call if_changed_dep,cpp_s_S)

quiet_cmd_as_o_S = AS $(quiet_modtag) $@
- cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
+ cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $< $(cmd_objtool)

ifdef CONFIG_ASM_MODVERSIONS

@@ -386,7 +378,7 @@ cmd_modversions_S = \
fi
endif

-$(obj)/%.o: $(src)/%.S $$(objtool_dep) FORCE
+$(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
$(call if_changed_rule,as_o_S)

targets += $(filter-out $(subdir-builtin), $(real-obj-y))
--
2.30.2