This patch adds lzip decompression support to the linux kernel. This
includes support for lzip-compressed kernel image, initramfs, initrd,
modules, and squashfs filesystems.

To apply the patch, first choose a version of the patch with the same
VERSION and PATCHLEVEL numbers as your kernel version. For example, if
you plan to patch linux-4.4.16, choose the patch file
linux-4.4.x_lzip-*.diff.lz.
If a patch for the desired VERSION-PATCHLEVEL combination does not
exist, you may request it in the lzip-bug list (see below).

Here is an example of how to apply the patch to version 4.7:

$ cd ~/linux-4.7
$ patch -p1 < ../linux-4.7_lzip-0.diff

Or if you prefer to apply the patch without decompressing it first:

$ cd ~/linux-4.7
$ lzip -cd ../linux-4.7_lzip-0.diff.lz | patch -p1

See Documentation/process/applying-patches.rst in the kernel tree for a
nice tutorial on the patch program.

Please, send bug reports, suggestions, requests, etc, about this patch
to <lzip-bug@nongnu.org>.

Documentation/lzip.txt follows:
-----------------------------------------------------------------------

==============================
Lzip data compression in Linux
==============================

Introduction
============

Lzip is a lossless data compressor with a user interface similar to the
one of gzip or bzip2. Lzip can compress about as fast as gzip (lzip -0),
or compress most files more than bzip2 (lzip -9). Decompression speed is
intermediate between gzip and bzip2. Lzip implements the LZMA algorithm.

Lzip has been designed, written and tested with great care to be the
standard general-purpose compressor for unix-like systems. The lzip
format is as simple as possible (but not simpler). It provides accurate
and robust 3 factor integrity checking.

Learn more about lzip at http://www.nongnu.org/lzip/lzip.html

Lzip related components in the kernel
=====================================

The lzip_decompress module in lib/lzip.c provides a versatile lzip
decompression function able to do buffer to buffer decompression or
stream decompression with fill and flush callback functions. The usage
of the function is documented in include/linux/lzip.h.

For decompressing the kernel image, initramfs, and initrd, there is a
wrapper function in lib/decompress_lunzip.c providing the same common
interface as the other decompress_*.c files, which is defined in
include/linux/decompress/generic.h.

For kernel makefiles, two commands are provided in scripts/Makefile.lib
for use with $(call if_changed). The kernel image must be compressed
with $(call if_changed,klzip) which will append a four-byte trailer
containing the size of the uncompressed data, which is needed by the
boot code. Other things should be compressed with $(call if_changed,lzip).

Testing
=======

Lzip-compressed kernel images of multiple linux versions since 2.6.30.10
have been built and tested, even on machines as modest as an AMD 486-DX2
at 66 MHz with 64 MiB of RAM. In the worst case (on the slow machine
above), lzip just increased the boot time a 15% compared with gzip. On
more modern machines, lzip may boot slightly faster than gzip. It just
takes 0.2 seconds for lzip to decompress vmlinuz-4.4.16 on my machine.

Decompression time is usually a small fraction of the total boot time.
For example, using lz4 on a desktop machine in order to save 0.05
seconds of a total boot time of 20 seconds is probably not worth the
increased image size.

Xlunzip is a test tool for the lzip_decompress module. It is similar to
lunzip, but it uses the lzip_decompress module as a backend. The xlunzip
home page is at http://www.nongnu.org/lzip/xlunzip.html

Author: Antonio Diaz Diaz
Updated: 2018-07-08