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Use LZMA2 options that match the arch-specific alignment of instructions. This change reduces compressed kernel size 0-2 % depending on the arch. On 1-byte-aligned x86 it makes no difference and on 4-byte-aligned archs it helps the most. Use the ARM-Thumb filter for ARM-Thumb2 kernels. This reduces compressed kernel size about 5 %.[1] Previously such kernels were compressed using the ARM filter which didn't do anything useful with ARM-Thumb2 code. Add BCJ filter support for ARM64 and RISC-V. Compared to unfiltered XZ or plain LZMA, the compressed kernel size is reduced about 5 % on ARM64 and 7 % on RISC-V. A new enough version of the xz tool is required: 5.4.0 for ARM64 and 5.6.0 for RISC-V. With an old xz version, a message is printed to standard error and the kernel is compressed without the filter. Update lib/decompress_unxz.c to match the changes to xz_wrap.sh. Update the CONFIG_KERNEL_XZ help text in init/Kconfig: - Add the RISC-V and ARM64 filters. - Clarify that the PowerPC filter is for big endian only. - Omit IA-64. Link: https://lore.kernel.org/lkml/1637379771-39449-1-git-send-email-zhongjubin@huawei.com/ [1] Link: https://lkml.kernel.org/r/20240721133633.47721-15-lasse.collin@tukaani.org Signed-off-by: Lasse Collin <lasse.collin@tukaani.org> Reviewed-by: Sam James <sam@gentoo.org> Cc: Simon Glass <sjg@chromium.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Jubin Zhong <zhongjubin@huawei.com> Cc: Jules Maselbas <jmaselbas@zdiv.net> Cc: Emil Renner Berthing <emil.renner.berthing@canonical.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Joel Stanley <joel@jms.id.au> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Krzysztof Kozlowski <krzk@kernel.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Rui Li <me@lirui.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.