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Commit ab76f3d7 authored by Alain Knaff's avatar Alain Knaff Committed by H. Peter Anvin
Browse files

bzip2/lzma: make internal initramfs compression configurable 



Impact: Avoids silent environment dependency

Make builtin initramfs compression an explicit configurable.  The
previous version would pick a compression based on the binaries which
were installed on the system, which could lead to unexpected results.
It is now explicitly configured, and not having the appropriate
binaries installed on the build host is simply an error.

Signed-off-by: default avatarAlain Knaff <alain@knaff.lu>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent ab59d3b7

usr/Kconfig

+62 −0
Original line number Diff line number Diff line
@@ -71,3 +71,65 @@ config RD_LZMA 
	help

	  Support loading of a lzma encoded initial ramdisk or cpio buffer

	  If unsure, say N.



choice

	prompt "Built-in initramfs compression mode"

	help

	  This setting is only meaningful if the INITRAMFS_SOURCE is

	  set. It decides by which algorithm the INITRAMFS_SOURCE will

	  be compressed.

	  Several compression algorithms are available, which differ

	  in efficiency, compression and decompression speed.

	  Compression speed is only relevant when building a kernel.

	  Decompression speed is relevant at each boot.



	  If you have any problems with bzip2 or lzma compressed

	  initramfs, mail me (Alain Knaff) <alain@knaff.lu>.



	  High compression options are mostly useful for users who

	  are low on disk space (embedded systems), but for whom ram

	  size matters less.



	  If in doubt, select 'gzip'



config INITRAMFS_COMPRESSION_NONE

	bool "None"

	help

	  Do not compress the built-in initramfs at all. This may

	  sound wasteful in space, but, you should be aware that the

	  built-in initramfs will be compressed at a later stage

	  anyways along with the rest of the kernel, on those

	  architectures that support this.

	  However, not compressing the initramfs may lead to slightly

	  higher memory consumption during a short time at boot, while

	  both the cpio image and the unpacked filesystem image will

	  be present in memory simultaneously



config INITRAMFS_COMPRESSION_GZIP

	bool "Gzip"

	depends on RD_GZIP

	help

	  The old and tried gzip compression. Its compression ratio is

	  the poorest among the 3 choices; however its speed (both

	  compression and decompression) is the fastest.



config INITRAMFS_COMPRESSION_BZIP2

	bool "Bzip2"

	depends on RD_BZIP2

	help

	  Its compression ratio and speed is intermediate.

	  Decompression speed is slowest among the three.  The initramfs

	  size is about 10% smaller with bzip2, in comparison to gzip.

	  Bzip2 uses a large amount of memory. For modern kernels you

	  will need at least 8MB RAM or more for booting.



config INITRAMFS_COMPRESSION_LZMA

	bool "LZMA"

	depends on RD_LZMA

	help

	  The most recent compression algorithm.

	  Its ratio is best, decompression speed is between the other

	  two. Compression is slowest.	The initramfs size is about 33%

	  smaller with LZMA in comparison to gzip.



endchoice

usr/Makefile

+6 −12
Original line number Diff line number Diff line
@@ -5,24 +5,18 @@ 
klibcdirs:;

PHONY += klibcdirs



# Find out "preferred" ramdisk compressor. Order of preference is

#  1. bzip2 efficient, and likely to be present

#  2. gzip former default

#  3. lzma

#  4. none



# None of the above

suffix_y                   =



# Lzma, but no gzip nor bzip2

suffix_$(CONFIG_RD_LZMA)   = .lzma

# No compression

suffix_$(CONFIG_INITRAMFS_COMPRESSION_NONE)   =



# Gzip, but no bzip2

suffix_$(CONFIG_RD_GZIP)   = .gz

suffix_$(CONFIG_INITRAMFS_COMPRESSION_GZIP)   = .gz



# Bzip2

suffix_$(CONFIG_RD_BZIP2)  = .bz2

suffix_$(CONFIG_INITRAMFS_COMPRESSION_BZIP2)  = .bz2



# Lzma

suffix_$(CONFIG_INITRAMFS_COMPRESSION_LZMA)   = .lzma



# Generate builtin.o based on initramfs_data.o

obj-$(CONFIG_BLK_DEV_INITRD) := initramfs_data$(suffix_y).o