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

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Date:   Wed, 6 Apr 2022 11:13:18 -0700
From:   Jeff Johnson <quic_jjohnson@...cinc.com>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        <linux-kbuild@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH 7/7] kbuild: read *.mod to get objects passed to $(LD) or
 $(AR)

On 4/6/2022 8:30 AM, Masahiro Yamada 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.
> 
> 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)
>   

Looks like this also addresses the out-of-tree issue described in 
<https://lore.kernel.org/linux-kbuild/1610500731-30960-2-git-send-email-jjohnson@codeaurora.org/>

:)

/jeff