linux-kernel - Re: [PATCH 01/13] kbuild: move objtool_args back to scripts/Makefile.build

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Message-ID: <202108181944.C6006C032A@keescook>
Date:   Wed, 18 Aug 2021 19:45:32 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org,
        Sami Tolvanen <samitolvanen@...gle.com>,
        linux-kernel@...r.kernel.org,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH 01/13] kbuild: move objtool_args back to
 scripts/Makefile.build

On Thu, Aug 19, 2021 at 09:57:32AM +0900, Masahiro Yamada wrote:
> Commit b1a1a1a09b46 ("kbuild: lto: postpone objtool") moved objtool_args
> to Makefile.lib, so the arguments can be used in Makefile.modfinal as
> well as Makefile.build.
> 
> With commit 2b1d7fc05467 ("kbuild: Fix TRIM_UNUSED_KSYMS with
> LTO_CLANG"), module LTO linking came back to scripts/Makefile.build
> again.
> 
> So, there is no more reason to keep objtool_args separately in
> scripts/Makefile.lib.
> 
> Get it back to the original place, close to the objtool command.

Ah, yup. Good point. Nice cleanup.

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
> 
>  scripts/Makefile.build | 13 +++++++++++++
>  scripts/Makefile.lib   | 12 ------------
>  2 files changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index ea549579bfb7..31154e44c251 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -222,6 +222,19 @@ cmd_record_mcount = $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)),
>  endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
>  
>  ifdef CONFIG_STACK_VALIDATION
> +
> +# Objtool arguments are also needed for modfinal with LTO, so we define
> +# then here to avoid duplication.
> +objtool_args =								\
> +	$(if $(CONFIG_UNWINDER_ORC),orc generate,check)			\
> +	$(if $(part-of-module), --module,)				\
> +	$(if $(CONFIG_FRAME_POINTER),, --no-fp)				\
> +	$(if $(or $(CONFIG_GCOV_KERNEL),$(CONFIG_LTO_CLANG)),		\
> +		--no-unreachable,)					\
> +	$(if $(CONFIG_RETPOLINE), --retpoline,)				\
> +	$(if $(CONFIG_X86_SMAP), --uaccess,)				\
> +	$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount,)
> +
>  ifndef CONFIG_LTO_CLANG
>  
>  __objtool_obj := $(objtree)/tools/objtool/objtool
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index af1c920a585c..34c4c11c4bc1 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -232,18 +232,6 @@ ifeq ($(CONFIG_LTO_CLANG),y)
>  mod-prelink-ext := .lto
>  endif
>  
> -# Objtool arguments are also needed for modfinal with LTO, so we define
> -# then here to avoid duplication.
> -objtool_args =								\
> -	$(if $(CONFIG_UNWINDER_ORC),orc generate,check)			\
> -	$(if $(part-of-module), --module,)				\
> -	$(if $(CONFIG_FRAME_POINTER),, --no-fp)				\
> -	$(if $(or $(CONFIG_GCOV_KERNEL),$(CONFIG_LTO_CLANG)), 		\
> -		--no-unreachable,)					\
> -	$(if $(CONFIG_RETPOLINE), --retpoline,)				\
> -	$(if $(CONFIG_X86_SMAP), --uaccess,)				\
> -	$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount,)
> -
>  # Useful for describing the dependency of composite objects
>  # Usage:
>  #   $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add)
> -- 
> 2.30.2
> 

-- 
Kees Cook