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kbuild: rename cmd_{bzip2,lzma,lzo,lz4,xzkern,zstd22}

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GZIP-compressed files end with 4 byte data that represents the size
of the original input. The decompressors (the self-extracting kernel)
exploit it to know the vmlinux size beforehand. To mimic the GZIP's
trailer, Kbuild provides cmd_{bzip2,lzma,lzo,lz4,xzkern,zstd22}.
Unfortunately these macros are used everywhere despite the appended
size data is only useful for the decompressors.

There is no guarantee that such hand-crafted trailers are safely ignored.
In fact, the kernel refuses compressed initramdfs with the garbage data.
That is why usr/Makefile overrides size_append to make it no-op.

To limit the use of such broken compressed files, this commit renames
the existing macros as follows:

  cmd_bzip2   --> cmd_bzip2_with_size
  cmd_lzma    --> cmd_lzma_with_size
  cmd_lzo     --> cmd_lzo_with_size
  cmd_lz4     --> cmd_lz4_with_size
  cmd_xzkern  --> cmd_xzkern_with_size
  cmd_zstd22  --> cmd_zstd22_with_size

To keep the decompressors working, I updated the following Makefiles
accordingly:

  arch/arm/boot/compressed/Makefile
  arch/h8300/boot/compressed/Makefile
  arch/mips/boot/compressed/Makefile
  arch/parisc/boot/compressed/Makefile
  arch/s390/boot/compressed/Makefile
  arch/sh/boot/compressed/Makefile
  arch/x86/boot/compressed/Makefile

I reused the current macro names for the normal usecases; they produce
the compressed data in the proper format.

I did not touch the following:

  arch/arc/boot/Makefile
  arch/arm64/boot/Makefile
  arch/csky/boot/Makefile
  arch/mips/boot/Makefile
  arch/riscv/boot/Makefile
  arch/sh/boot/Makefile
  kernel/Makefile

This means those Makefiles will stop appending the size data.

I dropped the 'override size_append' hack from usr/Makefile.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
This commit is contained in:
Masahiro Yamada
2022-01-10 03:15:27 +09:00
parent 64d8aaa4ef
commit 7ce7e984ab
9 changed files with 58 additions and 43 deletions
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5
usr/Makefile
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@@ -3,11 +3,6 @@
# kbuild file for usr/ - including initramfs image
#
# cmd_bzip2, cmd_lzma, cmd_lzo, cmd_lz4 from scripts/Makefile.lib appends the
# size at the end of the compressed file, which unfortunately does not work
# with unpack_to_rootfs(). Make size_append no-op.
override size_append := :
compress-y := shipped
compress-$(CONFIG_INITRAMFS_COMPRESSION_GZIP) := gzip
compress-$(CONFIG_INITRAMFS_COMPRESSION_BZIP2) := bzip2