linux-kernel - Re: [PATCH v5 12/12] kbuild: rebuild multi-object modules when objtool is updated

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Date:   Fri, 13 May 2022 13:40:43 +0200
From:   Nicolas Schier <nicolas@...sle.eu>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-modules@...r.kernel.org, llvm@...ts.linux.dev,
        Ard Biesheuvel <ardb@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH v5 12/12] kbuild: rebuild multi-object modules when
 objtool is updated

On Thu, May 12, 2022 at 01:45:14AM +0900, Masahiro Yamada wrote:
> When CONFIG_LTO_CLANG or CONFIG_X86_KERNEL_IBT is enabled, objtool for
> multi-object modules is postponed until the objects are linked together.
> 
> Make sure to re-run objtool and re-link multi-object modules when
> objtool is updated.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
> ---
> 
> (no changes since v4)
> 
> Changes in v4:
>   - New
>     Resent of my previous submission
>     https://lore.kernel.org/linux-kbuild/20210831074004.3195284-11-masahiroy@kernel.org/
> 
>  scripts/Makefile.build | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index f546b5f1f33f..4e6902e099e8 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -404,13 +404,18 @@ $(obj)/modules.order: $(obj-m) FORCE
>  $(obj)/lib.a: $(lib-y) FORCE
>  	$(call if_changed,ar)
>  
> -quiet_cmd_link_multi-m = LD [M]  $@
> -      cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ @$(patsubst %.o,%.mod,$@) $(cmd_objtool)
> +quiet_cmd_ld_multi_m = LD [M]  $@
> +      cmd_ld_multi_m = $(LD) $(ld_flags) -r -o $@ @$(patsubst %.o,%.mod,$@) $(cmd_objtool)
> +
> +define rule_ld_multi_m
> +	$(call cmd_and_savecmd,ld_multi_m)
> +	$(call cmd,gen_objtooldep)
> +endef
>  
>  $(multi-obj-m): objtool-enabled := $(delay-objtool)
>  $(multi-obj-m): part-of-module := y
>  $(multi-obj-m): %.o: %.mod FORCE
> -	$(call if_changed,link_multi-m)
> +	$(call if_changed_rule,ld_multi_m)
>  $(call multi_depend, $(multi-obj-m), .o, -objs -y -m)
>  
>  targets := $(filter-out $(PHONY), $(targets))
> -- 
> 2.32.0
> 

Reviewed-by: Nicolas Schier <n.schier@....de>