linux-kernel - Re: [PATCH 5/5] kbuild: add cmd_file

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Date:   Mon, 10 Jan 2022 12:33:40 +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 5/5] kbuild: add cmd_file_size

On Mon, Jan 10, 2022 at 03:15:29AM +0900, Masahiro Yamada wrote:
> Some architectures support self-extracting kernel, which embeds the
> compressed vmlinux.
> 
> It has 4 byte data at the end so the decompressor can know the vmlinux
> size beforehand.
> 
> GZIP natively has it in the trailer, but for the other compression
> algorithms, the hand-crafted trailer is added.
> 
> It is unneeded to generate such _corrupted_ compressed files because
> it is possible to pass the size data separately.
> 
> For example, the assembly code:
> 
>      .incbin "compressed-vmlinux-with-size-data-appended"
> 
> can be transformed to:
> 
>      .incbin "compressed-vmlinux"
>      .incbin "size-data"
> 
> My hope is, after some reworks of the decompressors, the macros
> cmd_{bzip2,lzma,lzo,lz4,xzkern,zstd22} will go away.
> 
> This new macro, cmd_file_size, will be useful to generate a separate
> size-data file.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---

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

> 
>  scripts/Makefile.lib | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 4207a72d429f..05ca77706f6b 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -394,6 +394,9 @@ printf "%08x\n" $$dec_size |						\
>  	}								\
>  )
>  
> +quiet_cmd_file_size = GEN     $@
> +      cmd_file_size = $(size_append) > $@
> +
>  quiet_cmd_bzip2 = BZIP2   $@
>        cmd_bzip2 = cat $(real-prereqs) | $(KBZIP2) -9 > $@
>  
> -- 
> 2.32.0
>