linux-kernel - Re: [PATCH v2 03/13] kbuild: store the objtool command in *.cmd files

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Date:   Tue, 31 Aug 2021 10:23:10 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH v2 03/13] kbuild: store the objtool command in *.cmd files

On Tue, Aug 31, 2021 at 12:40 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> objtool_dep includes include/config/{ORC_UNWINDER,STACK_VALIDATION}
> so that all the objects are rebuilt when any of CONFIG_ORC_UNWINDER
> and CONFIG_STACK_VALIDATION is toggled.
>
> As you can see in 'objtool_args', there are more CONFIG options
> that affect the objtool command line.
>
> Adding more and more include/config/* is ugly and unmaintainable.
>
> Another issue is that non-standard objects are needlessly rebuilt.
> Objects specified as OBJECT_FILES_NON_STANDARD is not processed by
> objtool, but they are rebuilt anyway when CONFIG_ORC_UNWINDER or
> CONFIG_STACK_VALIDATION is toggled. This is not a big deal, but
> better to fix.
>
> A cleaner and more precise 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@...nel.org>

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>
>  scripts/Makefile.build | 14 +++++---------
>  1 file changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index e78096cd396b..021ae0146913 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:
> @@ -243,7 +243,7 @@ ifndef CONFIG_LTO_CLANG
>  # '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) $(objtool_args) $@)
> +       ; $(objtool) $(objtool_args) $@)
>  objtool_obj = $(if $(patsubst y%,, \
>         $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
>         $(objtool))
> @@ -251,10 +251,8 @@ objtool_obj = $(if $(patsubst y%,, \
>  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)
> +# Rebuild all objects when objtool changes
> +objtool_dep = $(objtool_obj)
>
>  ifdef CONFIG_TRIM_UNUSED_KSYMS
>  cmd_gen_ksymdeps = \
> @@ -269,7 +267,6 @@ 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
> @@ -277,7 +274,6 @@ 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
>
> @@ -365,7 +361,7 @@ $(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
>
> --
> 2.30.2
>


-- 
Thanks,
~Nick Desaulniers