linux-kernel - Re: [PATCH 7/7] kbuild: read *.mod to get objects passed to $(LD) or $(AR)

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Message-ID: <CAKwvOdkjPcLvv-AnG+JnP+k_eGd-sZoDwjZuVf6nkp5LyxWXtA@mail.gmail.com>
Date:   Thu, 7 Apr 2022 11:01:17 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michal Marek <michal.lkml@...kovi.net>
Subject: Re: [PATCH 7/7] kbuild: read *.mod to get objects passed to $(LD) or $(AR)

On Wed, Apr 6, 2022 at 8:31 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> ld and ar support @file, which command-line options are read from.
>
> Now that *.mod lists the member objects in the correct order, without
> duplication, it is ready to be passed to ld and ar.
>
> By using the @file syntax, people will not be worried about the pitfall
> described in the NOTE.

Clever! Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  scripts/Makefile.build | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 3da731cf6978..f6a506318795 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -450,22 +450,18 @@ quiet_cmd_ar_lib = AR      $@
>  $(obj)/lib.a: $(lib-y) FORCE
>         $(call if_changed,ar_lib)
>
> -# NOTE:
> -# Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
> -# module is turned into a multi object module, $^ will contain header file
> -# dependencies recorded in the .*.cmd file.
>  ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
>  quiet_cmd_link_multi-m = AR [M]  $@
>  cmd_link_multi-m =                                             \
>         $(cmd_update_lto_symversions);                          \
>         rm -f $@;                                               \
> -       $(AR) cDPrsT $@ $(filter %.o,$^)
> +       $(AR) cDPrsT $@ @$(patsubst %.o,%.mod,$@)
>  else
>  quiet_cmd_link_multi-m = LD [M]  $@
> -      cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
> +      cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ @$(patsubst %.o,%.mod,$@)
>  endif
>
> -$(multi-obj-m): FORCE
> +$(multi-obj-m): %.o: %.mod FORCE
>         $(call if_changed,link_multi-m)
>  $(call multi_depend, $(multi-obj-m), .o, -objs -y -m)
>
> --
> 2.32.0
>


-- 
Thanks,
~Nick Desaulniers