|author||Lasse Collin <firstname.lastname@example.org>||2011-01-12 17:01:23 -0800|
|committer||Linus Torvalds <email@example.com>||2011-01-13 08:03:25 -0800|
decompressors: add boot-time XZ support
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 <firstname.lastname@example.org> Cc: "H. Peter Anvin" <email@example.com> Cc: Alain Knaff <firstname.lastname@example.org> Cc: Albin Tonnerre <email@example.com> Cc: Phillip Lougher <firstname.lastname@example.org> Signed-off-by: Andrew Morton <email@example.com> Signed-off-by: Linus Torvalds <firstname.lastname@example.org>
Diffstat (limited to 'init')
1 files changed, 19 insertions, 1 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 8dfd094e687..ea176e8edbd 100644
@@ -130,13 +130,16 @@ config HAVE_KERNEL_BZIP2
prompt "Kernel compression mode"
- 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
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.
+ bool "XZ"
+ depends on HAVE_KERNEL_XZ
+ 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.
depends on HAVE_KERNEL_LZO