lib: add support for LZO-compressed kernels

This patch series adds generic support for creating and extracting
LZO-compressed kernel images, as well as support for using such images on
the x86 and ARM architectures, and support for creating and using
LZO-compressed initrd and initramfs images.

Russell King said:

: Testing on a Cortex A9 model:
: - lzo decompressor is 65% of the time gzip takes to decompress a kernel
: - lzo kernel is 9% larger than a gzip kernel
:
: which I'm happy to say confirms your figures when comparing the two.
:
: However, when comparing your new gzip code to the old gzip code:
: - new is 99% of the size of the old code
: - new takes 42% of the time to decompress than the old code
:
: What this means is that for a proper comparison, the results get even better:
: - lzo is 7.5% larger than the old gzip'd kernel image
: - lzo takes 28% of the time that the old gzip code took
:
: So the expense seems definitely worth the effort.  The only reason I
: can think of ever using gzip would be if you needed the additional
: compression (eg, because you have limited flash to store the image.)
:
: I would argue that the default for ARM should therefore be LZO.

This patch:

The lzo compressor is worse than gzip at compression, but faster at
extraction.  Here are some figures for an ARM board I'm working on:

Uncompressed size: 3.24Mo
gzip  1.61Mo 0.72s
lzo   1.75Mo 0.48s

So for a compression ratio that is still relatively close to gzip, it's
much faster to extract, at least in that case.

This part contains:
 - Makefile routine to support lzo compression
 - Fixes to the existing lzo compressor so that it can be used in
   compressed kernels
 - wrapper around the existing lzo1x_decompress, as it only extracts one
   block at a time, while we need to extract a whole file here
 - config dialog for kernel compression

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: cleanup]
Signed-off-by: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Tested-by: Wu Zhangjin <wuzhangjin@gmail.com>
Acked-by: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Russell King <rmk@arm.linux.org.uk>
Acked-by: Russell King <rmk@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 4 deletions

diff --git a/init/Kconfig b/init/Kconfig
index a23da9f01803..d95ca7cd5d45 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -115,10 +115,13 @@ config HAVE_KERNEL_BZIP2
 config HAVE_KERNEL_LZMA
 	bool
 
+config HAVE_KERNEL_LZO
+	bool
+
 choice
 	prompt "Kernel compression mode"
 	default KERNEL_GZIP
-	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
+	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
 	help
 	  The linux kernel is a kind of self-extracting executable.
 	  Several compression algorithms are available, which differ
@@ -141,9 +144,8 @@ config KERNEL_GZIP
 	bool "Gzip"
 	depends on HAVE_KERNEL_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.
+	  The old and tried gzip compression. It provides a good balance
+	  between compression ratio and decompression speed.
 
 config KERNEL_BZIP2
 	bool "Bzip2"
@@ -164,6 +166,14 @@ config KERNEL_LZMA
 	  two. Compression is slowest.	The kernel size is about 33%
 	  smaller with LZMA in comparison to gzip.
 
+config KERNEL_LZO
+	bool "LZO"
+	depends on HAVE_KERNEL_LZO
+	help
+	  Its compression ratio is the poorest among the 4. The kernel
+	  size is about about 10% bigger than gzip; however its speed
+	  (both compression and decompression) is the fastest.
+
 endchoice
 
 config SWAP