linux-kernel - Re: [PATCH 2/5] kbuild: drop $(size_append) from cmd

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Date:   Mon, 10 Jan 2022 12:32:55 +0100
From:   Nicolas Schier <n.schier@....de>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: Re: [PATCH 2/5] kbuild: drop $(size_append) from cmd_zstd

On Mon, Jan 10, 2022 at 03:15:26AM +0900, Masahiro Yamada wrote:
> The appended file size is only used by the decompressors, which some
> architectures support.
> 
> As the comment "zstd22 is used for kernel compression" says, cmd_zstd22
> is used in arch/{mips,s390,x86}/boot/compressed/Makefile.
> 
> On the other hand, there is no good reason to append the file size to
> cmd_zstd since it is used for other purposes.
> 
> Actually cmd_zstd is only used in usr/Makefile, where the appended file
> size is rather harmful.
> 
> The initramfs with its file size appended is considered as corrupted
> data, so commit 65e00e04e5ae ("initramfs: refactor the initramfs build
> rules") added 'override size_append := :' to make it no-op.
> 
> As a conclusion, this $(size_append) should not exist here.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---

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


> 
>  scripts/Makefile.lib | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index d1f865b8c0cb..5366466ea0e4 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -473,7 +473,7 @@ quiet_cmd_xzmisc = XZMISC  $@
>  # be used because it would require zstd to allocate a 128 MB buffer.
>  
>  quiet_cmd_zstd = ZSTD    $@
> -      cmd_zstd = { cat $(real-prereqs) | $(ZSTD) -19; $(size_append); } > $@
> +      cmd_zstd = cat $(real-prereqs) | $(ZSTD) -19 > $@
>  
>  quiet_cmd_zstd22 = ZSTD22  $@
>        cmd_zstd22 = { cat $(real-prereqs) | $(ZSTD) -22 --ultra; $(size_append); } > $@
> -- 
> 2.32.0
>