linux-kernel - Re: [PATCH v2 2/2] kbuild: lto: preserve MAKEFLAGS for module linking

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Message-ID: <CAK7LNATNy6-W+9USiO1pEK1syj1M1fVB1Zda2NuDmPogVp4cmQ@mail.gmail.com>
Date:   Tue, 19 Jul 2022 18:15:40 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Martin Liska <mliska@...e.cz>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v2 2/2] kbuild: lto: preserve MAKEFLAGS for module linking

On Tue, Jul 19, 2022 at 5:41 PM Jiri Slaby <jslaby@...e.cz> wrote:
>
> From: Martin Liska <mliska@...e.cz>
>
> Prefix command in makefile run in order to preserve access to jobserver.
> This is needed for gcc at least.
>
> Fixes this warning:
> lto-wrapper: warning: jobserver is not available: ‘--jobserver-auth=’ is not present in ‘MAKEFLAGS’


What is lto-wrapper ?

>
> Cc: Sedat Dilek <sedat.dilek@...il.com>
> Cc: Masahiro Yamada <masahiroy@...nel.org>
> Cc: Michal Marek <michal.lkml@...kovi.net>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Fixes: 5d45950dfbb1 (kbuild: move vmlinux.o link to scripts/Makefile.vmlinux_o)
> Signed-off-by: Martin Liska <mliska@...e.cz>
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> ---
>
> Notes:
>     [v2] this is new in v2
>
>  scripts/Makefile.build | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index bb63374fb055..493f3c4e8461 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -247,8 +247,8 @@ endef
>
>  # Built-in and composite module parts
>  $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
> -       $(call if_changed_rule,cc_o_c)
> -       $(call cmd,force_checksrc)
> +       +$(call if_changed_rule,cc_o_c)
> +       +$(call cmd,force_checksrc)


cmd_force_checksrc invokes sparse.
How is it related to GCC?




>
>  # To make this rule robust against "Argument list too long" error,
>  # ensure to add $(obj)/ prefix by a shell command.
> @@ -457,7 +457,7 @@ endef
>  $(multi-obj-m): objtool-enabled := $(delay-objtool)
>  $(multi-obj-m): part-of-module := y
>  $(multi-obj-m): %.o: %.mod FORCE
> -       $(call if_changed_rule,ld_multi_m)
> +       +$(call if_changed_rule,ld_multi_m)
>  $(call multi_depend, $(multi-obj-m), .o, -objs -y -m)


cmd_ld_multi_m invokes $(LD) directly.
How is it related to gcc?






>
>  targets := $(filter-out $(PHONY), $(targets))
> --
> 2.37.1
>


-- 
Best Regards
Masahiro Yamada