Re: [PATCH 5/5] kbuild: add cmd_file_size

Nicolas Schier
2022-01-10T11:35:03Z

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@kernel.org>
> ---

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