Re: [PATCH 2/5] kbuild: detect objtool changes correctly without .SECONDEXPANSION
From: Masahiro Yamada <masahiroy@kernel.org>
Date: 2021-08-31 01:44:51
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On Sat, Aug 28, 2021 at 6:51 PM Masahiro Yamada [off-list ref] wrote:
This reverts commit 8852c5524029 ("kbuild: Fix objtool dependency for
'OBJECT_FILES_NON_STANDARD_<obj> := n'"), and fixes the dependency in
a cleaner, more precise 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.
Also, include the md5sum of objtool into *.cmd files so any change in
the objtool executable will result in rebuilding all objects that depend
on objtool.After more consideration, I decided not to do this. (I retract 2/5, 4/5, 5/5 from this series). I came up with a cleaner patch set. I will send it later.
quoted hunk ↗ jump to hunk
This allows us to drop $(objtool_deps) entirely. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- Makefile | 3 ++- scripts/Makefile.build | 26 +++++++++----------------- scripts/link-vmlinux.sh | 3 ++- 3 files changed, 13 insertions(+), 19 deletions(-)diff --git a/Makefile b/Makefile index 829bd339ffdc..3ef3685b7e4a 100644 --- a/Makefile +++ b/Makefile@@ -1858,7 +1858,8 @@ descend: $(build-dirs) $(build-dirs): prepare $(Q)$(MAKE) $(build)=$@ \ single-build=$(if $(filter-out $@/, $(filter $@/%, $(KBUILD_SINGLE_TARGETS))),1) \ - need-builtin=1 need-modorder=1 + need-builtin=1 need-modorder=1 \ + $(if $(CONFIG_STACK_VALIDATION),objtool-md5sum=$(firstword $(shell md5sum tools/objtool/objtool))) clean-dirs := $(addprefix _clean_, $(clean-dirs)) PHONY += $(clean-dirs) cleandiff --git a/scripts/Makefile.build b/scripts/Makefile.build index 3efc984d4c69..8aa6eaa4bf21 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:@@ -226,26 +226,21 @@ endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT ifdef CONFIG_STACK_VALIDATION ifndef CONFIG_LTO_CLANG -__objtool_obj := $(objtree)/tools/objtool/objtool +objtool := $(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 +# +# Record the md5sum of the objtool executable so any change in it results in +# rebuilding objects. 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-md5sum) ; $(objtool) $(objtool_args) $@) 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@@ -259,7 +254,6 @@ 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@@ -267,13 +261,11 @@ 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) $$(objtool_dep) FORCE +$(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE $(call if_changed_rule,cc_o_c) $(call cmd,force_checksrc)@@ -356,7 +348,7 @@ $(obj)/%.s: $(src)/%.S FORCE $(call if_changed_dep,cpp_s_S) quiet_cmd_as_o_S = AS $(quiet_modtag) $@ - cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $< + cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $< $(cmd_objtool) ifdef CONFIG_ASM_MODVERSIONS@@ -375,7 +367,7 @@ cmd_modversions_S = \ fi endif -$(obj)/%.o: $(src)/%.S $$(objtool_dep) FORCE +$(obj)/%.o: $(src)/%.S FORCE $(call if_changed_rule,as_o_S) targets += $(filter-out $(subdir-builtin), $(real-obj-y))diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index d74cee5c4326..58b3a94c934b 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh@@ -335,7 +335,8 @@ else fi; # final build of init/ -${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1 +${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1 \ + ${CONFIG_STACK_VALIDATION:+objtool-md5sum=$(md5sum tools/objtool/objtool | cut -d ' ' -f1)} #link vmlinux.o modpost_link vmlinux.o --2.30.2
-- Best Regards Masahiro Yamada