#!/bin/sh# SPDX-License-Identifier: 0BSD## This is a wrapper for xz to compress the kernel image using appropriate# compression options depending on the architecture.## Author: Lasse Collin <lasse.collin@tukaani.org> # This has specialized settings for the following archs. However,# XZ-compressed kernel isn't currently supported on every listed arch.##   Arch        Align   Notes#   arm          2/4    ARM and ARM-Thumb2#   arm64         4#   csky          2#   loongarch     4#   mips         2/4    MicroMIPS is 2-byte aligned#   parisc        4#   powerpc       4     Uses its own wrapper for compressors instead of this.#   riscv        2/4#   s390          2#   sh            2#   sparc         4#   x86           1 # A few archs use 2-byte or 4-byte aligned instructions depending on# the kernel config. This function is used to check if the relevant# config option is set to "y".is_enabled(){	grep -q "^$1=y$" include/config/auto.conf} # XZ_VERSION is needed to disable features that aren't available in# old XZ Utils versions.XZ_VERSION=$($XZ --robot --version) || exitXZ_VERSION=$(printf '%s\n' "$XZ_VERSION" | sed -n 's/^XZ_VERSION=//p') # Assume that no BCJ filter is available.BCJ= # Set the instruction alignment to 1, 2, or 4 bytes.## Set the BCJ filter if one is available.# It must match the #ifdef usage in lib/decompress_unxz.c.case $SRCARCH in	arm)		if is_enabled CONFIG_THUMB2_KERNEL; then			ALIGN=2			BCJ=--armthumb		else			ALIGN=4			BCJ=--arm		fi		;; 	arm64)		ALIGN=4 		# ARM64 filter was added in XZ Utils 5.4.0.		if [ "$XZ_VERSION" -ge 50040002 ]; then			BCJ=--arm64		else			echo "$0: Upgrading to xz >= 5.4.0" \				"would enable the ARM64 filter" \				"for better compression" >&2		fi		;; 	csky)		ALIGN=2		;; 	loongarch)		ALIGN=4		;; 	mips)		if is_enabled CONFIG_CPU_MICROMIPS; then			ALIGN=2		else			ALIGN=4		fi		;; 	parisc)		ALIGN=4		;; 	powerpc)		ALIGN=4 		# The filter is only for big endian instruction encoding.		if is_enabled CONFIG_CPU_BIG_ENDIAN; then			BCJ=--powerpc		fi		;; 	riscv)		if is_enabled CONFIG_RISCV_ISA_C; then			ALIGN=2		else			ALIGN=4		fi 		# RISC-V filter was added in XZ Utils 5.6.0.		if [ "$XZ_VERSION" -ge 50060002 ]; then			BCJ=--riscv		else			echo "$0: Upgrading to xz >= 5.6.0" \				"would enable the RISC-V filter" \				"for better compression" >&2		fi		;; 	s390)		ALIGN=2		;; 	sh)		ALIGN=2		;; 	sparc)		ALIGN=4		BCJ=--sparc		;; 	x86)		ALIGN=1		BCJ=--x86		;; 	*)		echo "$0: Arch-specific tuning is missing for '$SRCARCH'" >&2 		# Guess 2-byte-aligned instructions. Guessing too low		# should hurt less than guessing too high.		ALIGN=2		;;esac # Select the LZMA2 options matching the instruction alignment.case $ALIGN in	1)  LZMA2OPTS= ;;	2)  LZMA2OPTS=lp=1 ;;	4)  LZMA2OPTS=lp=2,lc=2 ;;	*)  echo "$0: ALIGN wrong or missing" >&2; exit 1 ;;esac # Use single-threaded mode because it compresses a little better# (and uses less RAM) than multithreaded mode.## For the best compression, the dictionary size shouldn't be# smaller than the uncompressed kernel. 128 MiB dictionary# needs less than 1400 MiB of RAM in single-threaded mode.## On the archs that use this script to compress the kernel,# decompression in the preboot code is done in single-call mode.# Thus the dictionary size doesn't affect the memory requirements# of the preboot decompressor at all.exec $XZ --check=crc32 --threads=1 $BCJ --lzma2=$LZMA2OPTS,dict=128MiB