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git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git
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Lasse Collin
7472ff8ada
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/[email protected]/ [1] Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Lasse Collin <[email protected]> Reviewed-by: Sam James <[email protected]> Cc: Simon Glass <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: Will Deacon <[email protected]> Cc: Paul Walmsley <[email protected]> Cc: Palmer Dabbelt <[email protected]> Cc: Albert Ou <[email protected]> Cc: Jubin Zhong <[email protected]> Cc: Jules Maselbas <[email protected]> Cc: Emil Renner Berthing <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Herbert Xu <[email protected]> Cc: Joel Stanley <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Krzysztof Kozlowski <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Randy Dunlap <[email protected]> Cc: Rui Li <[email protected]> Cc: Thomas Gleixner <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
163 lines
3.4 KiB
Bash
Executable File
163 lines
3.4 KiB
Bash
Executable File
#!/bin/sh
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# SPDX-License-Identifier: 0BSD
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#
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# This is a wrapper for xz to compress the kernel image using appropriate
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# compression options depending on the architecture.
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#
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# Author: Lasse Collin <[email protected]>
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# This has specialized settings for the following archs. However,
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# XZ-compressed kernel isn't currently supported on every listed arch.
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#
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# Arch Align Notes
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# arm 2/4 ARM and ARM-Thumb2
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# arm64 4
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# csky 2
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# loongarch 4
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# mips 2/4 MicroMIPS is 2-byte aligned
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# parisc 4
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# powerpc 4 Uses its own wrapper for compressors instead of this.
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# riscv 2/4
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# s390 2
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# sh 2
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# sparc 4
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# x86 1
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# A few archs use 2-byte or 4-byte aligned instructions depending on
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# the kernel config. This function is used to check if the relevant
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# config option is set to "y".
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is_enabled()
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{
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grep -q "^$1=y$" include/config/auto.conf
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}
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# XZ_VERSION is needed to disable features that aren't available in
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# old XZ Utils versions.
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XZ_VERSION=$($XZ --robot --version) || exit
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XZ_VERSION=$(printf '%s\n' "$XZ_VERSION" | sed -n 's/^XZ_VERSION=//p')
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# Assume that no BCJ filter is available.
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BCJ=
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# Set the instruction alignment to 1, 2, or 4 bytes.
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#
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# Set the BCJ filter if one is available.
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# It must match the #ifdef usage in lib/decompress_unxz.c.
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case $SRCARCH in
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arm)
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if is_enabled CONFIG_THUMB2_KERNEL; then
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ALIGN=2
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BCJ=--armthumb
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else
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ALIGN=4
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BCJ=--arm
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fi
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;;
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arm64)
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ALIGN=4
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# ARM64 filter was added in XZ Utils 5.4.0.
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if [ "$XZ_VERSION" -ge 50040002 ]; then
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BCJ=--arm64
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else
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echo "$0: Upgrading to xz >= 5.4.0" \
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"would enable the ARM64 filter" \
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"for better compression" >&2
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fi
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;;
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csky)
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ALIGN=2
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;;
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loongarch)
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ALIGN=4
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;;
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mips)
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if is_enabled CONFIG_CPU_MICROMIPS; then
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ALIGN=2
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else
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ALIGN=4
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fi
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;;
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parisc)
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ALIGN=4
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;;
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powerpc)
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ALIGN=4
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# The filter is only for big endian instruction encoding.
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if is_enabled CONFIG_CPU_BIG_ENDIAN; then
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BCJ=--powerpc
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fi
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;;
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riscv)
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if is_enabled CONFIG_RISCV_ISA_C; then
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ALIGN=2
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else
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ALIGN=4
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fi
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# RISC-V filter was added in XZ Utils 5.6.0.
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if [ "$XZ_VERSION" -ge 50060002 ]; then
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BCJ=--riscv
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else
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echo "$0: Upgrading to xz >= 5.6.0" \
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"would enable the RISC-V filter" \
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"for better compression" >&2
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fi
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;;
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s390)
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ALIGN=2
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;;
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sh)
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ALIGN=2
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;;
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sparc)
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ALIGN=4
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BCJ=--sparc
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;;
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x86)
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ALIGN=1
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BCJ=--x86
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;;
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*)
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echo "$0: Arch-specific tuning is missing for '$SRCARCH'" >&2
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# Guess 2-byte-aligned instructions. Guessing too low
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# should hurt less than guessing too high.
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ALIGN=2
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;;
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esac
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# Select the LZMA2 options matching the instruction alignment.
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case $ALIGN in
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1) LZMA2OPTS= ;;
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2) LZMA2OPTS=lp=1 ;;
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4) LZMA2OPTS=lp=2,lc=2 ;;
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*) echo "$0: ALIGN wrong or missing" >&2; exit 1 ;;
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esac
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# Use single-threaded mode because it compresses a little better
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# (and uses less RAM) than multithreaded mode.
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#
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# For the best compression, the dictionary size shouldn't be
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# smaller than the uncompressed kernel. 128 MiB dictionary
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# needs less than 1400 MiB of RAM in single-threaded mode.
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#
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# On the archs that use this script to compress the kernel,
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# decompression in the preboot code is done in single-call mode.
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# Thus the dictionary size doesn't affect the memory requirements
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# of the preboot decompressor at all.
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exec $XZ --check=crc32 --threads=1 $BCJ --lzma2=$LZMA2OPTS,dict=128MiB
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