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 <lasse.collin@tukaani.org>
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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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