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

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Date:   Mon, 10 Jan 2022 03:15:29 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: [PATCH 5/5] kbuild: add cmd_file_size

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>
---

 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