From 3ebe12439ba7fc62e1d6ecb569b7287771716ca1 Mon Sep 17 00:00:00 2001 From: Lasse Collin Date: Wed, 12 Jan 2011 17:01:23 -0800 Subject: decompressors: add boot-time XZ support This implements the API defined in 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 Cc: "H. Peter Anvin" Cc: Alain Knaff Cc: Albin Tonnerre Cc: Phillip Lougher Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- init/Kconfig | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index 8dfd094e687..ea176e8edbd 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -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 -- cgit v1.2.3-18-g5258