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decompressors: add boot-time XZ support

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This implements the API defined in <linux/decompress/generic.h> which is
used for kernel, initramfs, and initrd decompression.  This patch together
with the first patch is enough for XZ-compressed initramfs and initrd;
XZ-compressed kernel will need arch-specific changes.

The buffering requirements described in decompress_unxz.c are stricter
than with gzip, so the relevant changes should be done to the
arch-specific code when adding support for XZ-compressed kernel.
Similarly, the heap size in arch-specific pre-boot code may need to be
increased (30 KiB is enough).

The XZ decompressor needs memmove(), memeq() (memcmp() == 0), and
memzero() (memset(ptr, 0, size)), which aren't available in all
arch-specific pre-boot environments.  I'm including simple versions in
decompress_unxz.c, but a cleaner solution would naturally be nicer.

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alain Knaff <alain@knaff.lu>
Cc: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Cc: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lasse Collin
2011-01-12 17:01:23 -08:00
committed by Linus Torvalds
parent 24fa0402a9
commit 3ebe12439b
9 changed files with 469 additions and 2 deletions
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20
init/Kconfig
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@@ -130,13 +130,16 @@ config HAVE_KERNEL_BZIP2
config HAVE_KERNEL_LZMA
bool
config HAVE_KERNEL_XZ
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 || HAVE_KERNEL_LZO
depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
help
The linux kernel is a kind of self-extracting executable.
Several compression algorithms are available, which differ
@@ -181,6 +184,21 @@ config KERNEL_LZMA
two. Compression is slowest. The kernel size is about 33%
smaller with LZMA in comparison to gzip.
config KERNEL_XZ
bool "XZ"
depends on HAVE_KERNEL_XZ
help
XZ uses the LZMA2 algorithm and instruction set specific
BCJ filters which can improve compression ratio of executable
code. The size of the kernel is about 30% smaller with XZ in
comparison to gzip. On architectures for which there is a BCJ
filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
will create a few percent smaller kernel than plain LZMA.
The speed is about the same as with LZMA: The decompression
speed of XZ is better than that of bzip2 but worse than gzip
and LZO. Compression is slow.
config KERNEL_LZO
bool "LZO"
depends on HAVE_KERNEL_LZO