mkroot/mkroot.sh - platform/external/toybox - Git at Google

 #!/bin/bash

 # ------------------------------ Part 1: Setup -------------------------------

 # Clear environment variables by restarting script w/bare minimum passed through
 [ -z "$NOCLEAR" ] && exec env -i NOCLEAR=1 HOME="$HOME" PATH="$PATH" \
     LINUX="$LINUX" CROSS="$CROSS" CROSS_COMPILE="$CROSS_COMPILE" "$0" "$@"

 ! [ -d mkroot ] && echo "Run mkroot/mkroot.sh from toybox source dir." && exit 1

 # assign command line NAME=VALUE args to env vars, the rest are packages
 for i in "$@"; do
   [ "${i/=/}" != "$i" ] && export "$i" || { [ "$i" != -- ] && PKG="$PKG $i"; }
 done

 # Set default directory locations (overrideable from command line)
 : ${TOP:=$PWD/root} ${BUILD:=$TOP/build} ${LOG:=$BUILD/log}
 : ${AIRLOCK:=$BUILD/airlock} ${CCC:=$PWD/ccc} ${PKGDIR:=$PWD/mkroot/root}

 announce() { printf "\033]2;$CROSS $*\007" >/dev/tty; printf "\n=== $*\n";}
 die() { echo "$@" >&2; exit 1; }

 # ----- Are we cross compiling (via CROSS_COMPILE= or CROSS=)

 if [ -n "$CROSS_COMPILE" ]; then
   # airlock needs absolute path
   [ -z "${X:=$(command -v "$CROSS_COMPILE"cc)}" ] && die "no ${CROSS_COMPILE}cc"
   CROSS_COMPILE="$(realpath -s "${X%cc}")"
   [ -z "$CROSS" ] && CROSS=${CROSS_COMPILE/*\//} CROSS=${CROSS/-*/}

 elif [ -n "$CROSS" ]; then # CROSS=all/allnonstop/$ARCH else list known $ARCHes
   [ ! -d "$CCC" ] && die "No ccc symlink to compiler directory."
   TARGETS="$(ls "$CCC" | sed -n 's/-.*//p' | sort -u)"

   if [ "${CROSS::3}" == all ]; then # loop calling ourselves for each target
     for i in $TARGETS; do
       "$0" "$@" CROSS=$i || [ "$CROSS" == allnonstop ] || exit 1
     done; exit

   else # Find matching cross compiler under ccc/ else list available targets
     CROSS_COMPILE="$(echo "$CCC/$CROSS"-*cross/bin/"$CROSS"*-cc)" # wildcard
     [ ! -e "$CROSS_COMPILE" ] && echo $TARGETS && exit # list available targets
     CROSS_COMPILE="${CROSS_COMPILE%cc}" # trim to prefix for cc/ld/as/nm/strip
   fi
 fi

 # Set per-target output directory (using "host" if not cross-compiling)
 : ${CROSS:=host} ${OUTPUT:=$TOP/$CROSS}

 # Verify selected compiler works
 ${CROSS_COMPILE}cc --static -xc - -o /dev/null <<< "int main(void){return 0;}"||
   die "${CROSS_COMPILE}cc can't create static binaries"

 # ----- Create hermetic build environment

 if [ -z "$NOAIRLOCK"] && [ -n "$CROSS_COMPILE" ]; then
   # When cross compiling set host $PATH to binaries with known behavior by
   # - building a host toybox later builds use as their command line
   # - cherry-picking specific commands from old path via symlink
   if [ ! -e "$AIRLOCK/toybox" ]; then
     announce "airlock" &&
     PREFIX="$AIRLOCK" KCONFIG_CONFIG=.singleconfig_airlock CROSS_COMPILE= \
       make clean defconfig toybox install_airlock && # see scripts/install.sh
     rm .singleconfig_airlock || exit 1
   fi
   export PATH="$AIRLOCK"
   CPIO_OPTS+=--no-preserve-owner
 fi

 # Create per-target work directories
 TEMP="$BUILD/${CROSS}-tmp" && rm -rf "$TEMP" &&
 mkdir -p "$TEMP" "$OUTPUT" "$LOG" || exit 1
 [ -z "$ROOT" ] && ROOT="$OUTPUT/fs" && rm -rf "$ROOT"

 # ----- log build output

 # Install command line recording wrapper, logs all commands run from $PATH
 if [ -z "$NOLOGPATH" ]; then
   # Move cross compiler into $PATH so calls to it get logged
   [ -n "$CROSS_COMPILE" ] && PATH="${CROSS_COMPILE%/*}:$PATH" &&
     CROSS_COMPILE=${CROSS_COMPILE##*/}
   export WRAPDIR="$BUILD/record-commands" LOGPATH="$LOG/$CROSS-commands.txt"
   rm -rf "$WRAPDIR" "$LOGPATH" generated/obj &&
   WRAPDIR="$WRAPDIR" CROSS_COMPILE= NOSTRIP=1 source mkroot/record-commands ||
     exit 1
 fi

 # Start logging stdout/stderr
 rm -f "$LOG/$CROSS".{n,y} || exit 1
 [ -z "$NOLOG" ] && exec > >(tee "$LOG/$CROSS.n") 2>&1
 echo "Building for $CROSS"

 # ---------------------- Part 2: Create root filesystem -----------------------

 # ----- Create new root filesystem's directory layout.

 # FHS wants boot media opt srv usr/{local,share}, stuff under /var...
 mkdir -p "$ROOT"/{dev,etc/rc,home,mnt,proc,root,sys,tmp/run,usr/{bin,sbin,lib},var} &&
 chmod a+rwxt "$ROOT"/tmp && ln -s usr/{bin,sbin,lib} tmp/run "$ROOT" || exit 1

 # Write init script. Runs as pid 1 from initramfs to set up and hand off system.
 cat > "$ROOT"/init << 'EOF' &&
 #!/bin/sh

 export HOME=/home PATH=/bin:/sbin

 if ! mountpoint -q dev; then
   mount -t devtmpfs dev dev
   [ $$ -eq 1 ] && exec 0<>/dev/console 1>&0 2>&1
   for i in ,fd /0,stdin /1,stdout /2,stderr
   do ln -sf /proc/self/fd${i/,*/} dev/${i/*,/}; done
   mkdir -p dev/shm
   chmod +t /dev/shm
 fi
 mountpoint -q dev/pts || { mkdir -p dev/pts && mount -t devpts dev/pts dev/pts;}
 mountpoint -q proc || mount -t proc proc proc
 mountpoint -q sys || mount -t sysfs sys sys
 echo 0 99999 > /proc/sys/net/ipv4/ping_group_range

 if [ $$ -eq 1 ]; then # Setup networking for QEMU (needs /proc)
   mountpoint -q mnt || [ -e /dev/?da ] && mount /dev/?da /mnt
   ifconfig lo 127.0.0.1
   ifconfig eth0 10.0.2.15
   route add default gw 10.0.2.2
   [ "$(date +%s)" -lt 1000 ] && timeout 2 sntp -sq 10.0.2.2 # Ask host
   [ "$(date +%s)" -lt 10000000 ] && sntp -sq time.google.com

   # Run package scripts (if any)
   for i in $(ls -1 /etc/rc 2>/dev/null | sort); do . /etc/rc/"$i"; done

   [ -z "$HANDOFF" ] && [ -e /mnt/init ] && HANDOFF=/mnt/init
   [ -z "$HANDOFF" ] && HANDOFF=/bin/sh && echo -e '\e[?7hType exit when done.'
   echo 3 > /proc/sys/kernel/printk
   exec oneit $HANDOFF
 else # for chroot
   /bin/sh
   umount /dev/pts /dev /sys /proc
 fi
 EOF
 chmod +x "$ROOT"/init &&

 # Google's nameserver, passwd+group with special (root/nobody) accounts + guest
 echo "nameserver 8.8.8.8" > "$ROOT"/etc/resolv.conf &&
 cat > "$ROOT"/etc/passwd << 'EOF' &&
 root:x:0:0:root:/root:/bin/sh
 guest:x:500:500:guest:/home/guest:/bin/sh
 nobody:x:65534:65534:nobody:/proc/self:/dev/null
 EOF
 echo -e 'root:x:0:\nguest:x:500:\nnobody:x:65534:' > "$ROOT"/etc/group || exit 1

 # Build any packages listed on command line
 for i in ${PKG:+plumbing $PKG}; do
   pushd .
   announce "$i"; PATH="$PKGDIR:$PATH" source $i || die $i
   popd
 done

 # Build static toybox with existing .config if there is one, else defconfig+sh
 announce toybox
 [ -n "$PENDING" ] && rm -f .config
 [ -e .config ] && CONF=silentoldconfig || unset CONF
 for i in $PENDING sh route; do XX="$XX"$'\n'CONFIG_${i^^?}=y; done
 [ -e "$ROOT"/lib/libc.so ] || export LDFLAGS=--static
 PREFIX="$ROOT" make clean \
   ${CONF:-defconfig KCONFIG_ALLCONFIG=<(echo "$XX")} toybox install || exit 1
 unset LDFLAGS

 # ------------------ Part 3: Build + package bootable system ------------------

 # Convert comma separated values in $1 to CONFIG=$2 lines
 csv2cfg() { sed -E '/^$/d;s/([^,]*)($|,)/CONFIG_\1='"$2"'\n/g' <<< "$1"; }

 # ----- Build kernel for target

 if [ -z "$LINUX" ] || [ ! -d "$LINUX/kernel" ]; then
   echo 'No $LINUX directory, kernel build skipped.'
 else
   # Which architecture are we building a kernel for?
   LINUX="$(realpath "$LINUX")"
   [ -z "$TARGET" ] &&
     { [ "$CROSS" == host ] && TARGET="$(uname -m)" || TARGET="$CROSS"; }

   # Target-specific info in an (alphabetical order) if/else staircase
   # Each target needs board config, serial console, RTC, ethernet, block device.

   if [ "$TARGET" == armv5l ]; then
     # This could use the same VIRT board as armv7, but let's demonstrate a
     # different one requiring a separate device tree binary.
     QEMU="arm -M versatilepb -net nic,model=rtl8139 -net user"
     KARCH=arm KARGS=ttyAMA0 VMLINUX=arch/arm/boot/zImage
     KCONF=CPU_ARM926T,MMU,VFP,ARM_THUMB,AEABI,ARCH_VERSATILE,ATAGS,DEPRECATED_PARAM_STRUCT,ARM_ATAG_DTB_COMPAT,ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND,SERIAL_AMBA_PL011,SERIAL_AMBA_PL011_CONSOLE,RTC_CLASS,RTC_DRV_PL031,RTC_HCTOSYS,PCI,PCI_VERSATILE,BLK_DEV_SD,SCSI,SCSI_LOWLEVEL,SCSI_SYM53C8XX_2,SCSI_SYM53C8XX_MMIO,NET_VENDOR_REALTEK,8139CP
     KERNEL_CONFIG="CONFIG_SCSI_SYM53C8XX_DMA_ADDRESSING_MODE=0"
     DTB=arch/arm/boot/dts/versatile-pb.dtb
   elif [ "$TARGET" == armv7l ] || [ "$TARGET" == aarch64 ]; then
     if [ "$TARGET" == aarch64 ]; then
       QEMU="aarch64 -M virt -cpu cortex-a57"
       KARCH=arm64 VMLINUX=arch/arm64/boot/Image
     else
       QEMU="arm -M virt" KARCH=arm VMLINUX=arch/arm/boot/zImage
     fi
     KARGS=ttyAMA0
     KCONF=MMU,ARCH_MULTI_V7,ARCH_VIRT,SOC_DRA7XX,ARCH_OMAP2PLUS_TYPICAL,ARCH_ALPINE,ARM_THUMB,VDSO,CPU_IDLE,ARM_CPUIDLE,KERNEL_MODE_NEON,SERIAL_AMBA_PL011,SERIAL_AMBA_PL011_CONSOLE,RTC_CLASS,RTC_HCTOSYS,RTC_DRV_PL031,NET_CORE,VIRTIO_MENU,VIRTIO_NET,PCI,PCI_HOST_GENERIC,VIRTIO_BLK,VIRTIO_PCI,VIRTIO_MMIO,ATA,ATA_SFF,ATA_BMDMA,ATA_PIIX,PATA_PLATFORM,PATA_OF_PLATFORM,ATA_GENERIC,ARM_LPAE
   elif [ "$TARGET" == hexagon ]; then
     QEMU="hexagon -M comet" KARGS=ttyS0 VMLINUX=vmlinux
     KARCH="hexagon LLVM_IAS=1" KCONF=SPI,SPI_BITBANG,IOMMU_SUPPORT
   elif [ "$TARGET" == i486 ] || [ "$TARGET" == i686 ] ||
        [ "$TARGET" == x86_64 ] || [ "$TARGET" == x32 ]; then
     if [ "$TARGET" == i486 ]; then
       QEMU="i386 -cpu 486 -global fw_cfg.dma_enabled=false" KCONF=M486
     elif [ "$TARGET" == i686 ]; then
       QEMU="i386 -cpu pentium3" KCONF=MPENTIUMII
     else
       QEMU=x86_64 KCONF=64BIT
       [ "$TARGET" == x32 ] && KCONF=X86_X32
     fi
     KARCH=x86 KARGS=ttyS0 VMLINUX=arch/x86/boot/bzImage
     KCONF=$KCONF,UNWINDER_FRAME_POINTER,PCI,BLK_DEV_SD,ATA,ATA_SFF,ATA_BMDMA,ATA_PIIX,NET_VENDOR_INTEL,E1000,SERIAL_8250,SERIAL_8250_CONSOLE,RTC_CLASS
   elif [ "$TARGET" == m68k ]; then
     QEMU="m68k -M q800" KARCH=m68k KARGS=ttyS0 VMLINUX=vmlinux
     KCONF=MMU,M68040,M68KFPU_EMU,MAC,SCSI,SCSI_LOWLEVEL,BLK_DEV_SD,SCSI_MAC_ESP,MACINTOSH_DRIVERS,NET_CORE,NET_VENDOR_NATSEMI,MACSONIC,SERIAL_PMACZILOG,SERIAL_PMACZILOG_TTYS,SERIAL_PMACZILOG_CONSOLE
   elif [ "$TARGET" == mips ] || [ "$TARGET" == mipsel ]; then
     QEMU="mips -M malta" KARCH=mips KARGS=ttyS0 VMLINUX=vmlinux
     KCONF=MIPS_MALTA,CPU_MIPS32_R2,SERIAL_8250,SERIAL_8250_CONSOLE,PCI,BLK_DEV_SD,ATA,ATA_SFF,ATA_BMDMA,ATA_PIIX,NET_VENDOR_AMD,PCNET32,POWER_RESET,POWER_RESET_SYSCON
     [ "$TARGET" == mipsel ] && KCONF=$KCONF,CPU_LITTLE_ENDIAN &&
       QEMU="mipsel -M malta"
   elif [ "$TARGET" == powerpc ]; then
     KARCH=powerpc QEMU="ppc -M g3beige" KARGS=ttyS0 VMLINUX=vmlinux
     KCONF=ALTIVEC,PPC_PMAC,PPC_OF_BOOT_TRAMPOLINE,ATA,ATA_SFF,ATA_BMDMA,PATA_MACIO,BLK_DEV_SD,MACINTOSH_DRIVERS,ADB,ADB_CUDA,NET_VENDOR_NATSEMI,NET_VENDOR_8390,NE2K_PCI,SERIO,SERIAL_PMACZILOG,SERIAL_PMACZILOG_TTYS,SERIAL_PMACZILOG_CONSOLE,BOOTX_TEXT
   elif [ "$TARGET" == powerpc64 ] || [ "$TARGET" == powerpc64le ]; then
     KARCH=powerpc QEMU="ppc64 -M pseries -vga none" KARGS=hvc0
     VMLINUX=vmlinux
     KCONF=PPC64,PPC_PSERIES,PPC_OF_BOOT_TRAMPOLINE,BLK_DEV_SD,SCSI_LOWLEVEL,SCSI_IBMVSCSI,ATA,NET_VENDOR_IBM,IBMVETH,HVC_CONSOLE,PPC_TRANSACTIONAL_MEM,PPC_DISABLE_WERROR,SECTION_MISMATCH_WARN_ONLY
     [ "$TARGET" == powerpc64le ] && KCONF=$KCONF,CPU_LITTLE_ENDIAN
   elif [ "$TARGET" = s390x ]; then
     QEMU="s390x" KARCH=s390 VMLINUX=arch/s390/boot/bzImage
     KCONF=MARCH_Z900,PACK_STACK,NET_CORE,VIRTIO_NET,VIRTIO_BLK,SCLP_TTY,SCLP_CONSOLE,SCLP_VT220_TTY,SCLP_VT220_CONSOLE,S390_GUEST
   elif [ "$TARGET" == sh2eb ]; then
     BUILTIN=1 KARCH=sh VMLINUX=vmlinux
     KERNEL_CONFIG=$'CONFIG_MEMORY_START=0x10000000\nCONFIG_CMDLINE="console=ttyUL0 earlycon"'
     KCONF=CPU_SUBTYPE_J2,CPU_BIG_ENDIAN,SH_JCORE_SOC,SMP,BINFMT_ELF_FDPIC,JCORE_EMAC,SERIAL_UARTLITE,SERIAL_UARTLITE_CONSOLE,HZ_100,CMDLINE_OVERWRITE,SPI,SPI_JCORE,MMC,PWRSEQ_SIMPLE,MMC_BLOCK,MMC_SPI
   elif [ "$TARGET" == sh4 ]; then
     QEMU="sh4 -M r2d -serial null -serial mon:stdio" KARCH=sh
     KARGS="ttySC1 noiotrap" VMLINUX=arch/sh/boot/zImage
     KERNEL_CONFIG="CONFIG_MEMORY_START=0x0c000000"
     KCONF=CPU_SUBTYPE_SH7751R,MMU,VSYSCALL,SH_FPU,SH_RTS7751R2D,RTS7751R2D_PLUS,SERIAL_SH_SCI,SERIAL_SH_SCI_CONSOLE,PCI,NET_VENDOR_REALTEK,8139CP,PCI,BLK_DEV_SD,ATA,ATA_SFF,ATA_BMDMA,PATA_PLATFORM,BINFMT_ELF_FDPIC,BINFMT_FLAT
 #see also SPI SPI_SH_SCI MFD_SM501 RTC_CLASS RTC_DRV_R9701 RTC_DRV_SH RTC_HCTOSYS
   else die "Unknown \$TARGET $TARGET"
   fi

   # Write the qemu launch script
   if [ -n "$QEMU" ]; then
     [ -z "$BUILTIN" ] && INITRD="-initrd initramfs.cpio.gz"
     { echo qemu-system-"$QEMU" '"$@"' $QEMU_MORE -nographic -no-reboot -m 256 \
         -kernel linux-kernel $INITRD ${DTB:+-dtb linux.dtb} \
         "-append \"panic=1 HOST=$TARGET console=$KARGS \$KARGS\"" &&
       echo "echo -e '\\e[?7h'"
     } > "$OUTPUT"/run-qemu.sh &&
     chmod +x "$OUTPUT"/run-qemu.sh || exit 1
   fi

   announce "linux-$KARCH"
   pushd "$LINUX" && make distclean && popd &&
   cp -sfR "$LINUX" "$TEMP/linux" && pushd "$TEMP/linux" &&

   # Write linux-miniconfig
   { echo "# make ARCH=$KARCH allnoconfig KCONFIG_ALLCONFIG=linux-miniconfig"
     echo -e "# make ARCH=$KARCH -j \$(nproc)\n# boot $VMLINUX\n\n"

     # Expand list of =y symbols, first generic then architecture-specific
     for i in BINFMT_ELF,BINFMT_SCRIPT,NO_HZ,HIGH_RES_TIMERS,BLK_DEV,BLK_DEV_INITRD,RD_GZIP,BLK_DEV_LOOP,EXT4_FS,EXT4_USE_FOR_EXT2,VFAT_FS,FAT_DEFAULT_UTF8,MISC_FILESYSTEMS,SQUASHFS,SQUASHFS_XATTR,SQUASHFS_ZLIB,DEVTMPFS,DEVTMPFS_MOUNT,TMPFS,TMPFS_POSIX_ACL,NET,PACKET,UNIX,INET,IPV6,NETDEVICES,NET_CORE,NETCONSOLE,ETHERNET,COMPAT_32BIT_TIME,EARLY_PRINTK,IKCONFIG,IKCONFIG_PROC $KCONF $KEXTRA ; do
       echo "# architecture ${X:-independent}"
       csv2cfg "$i" y
       X=specific
     done
     [ -n "$BUILTIN" ] && echo -e CONFIG_INITRAMFS_SOURCE="\"$OUTPUT/fs\""
     for i in $MODULES; do csv2cfg "$i" m; done
     echo "$KERNEL_CONFIG"
   } > "$OUTPUT/linux-miniconfig" &&
   make ARCH=$KARCH allnoconfig KCONFIG_ALLCONFIG="$OUTPUT/linux-miniconfig" &&

   # Second config pass to remove stupid kernel defaults
   # See http://lkml.iu.edu/hypermail/linux/kernel/1912.3/03493.html
   sed -e 's/# CONFIG_EXPERT .*/CONFIG_EXPERT=y/' -e "$(sed -E -e '/^$/d' \
     -e 's@([^,]*)($|,)@/^CONFIG_\1=y/d;$a# CONFIG_\1 is not set\n@g' \
        <<< VT,SCHED_DEBUG,DEBUG_MISC,X86_DEBUG_FPU)" -i .config &&
   yes "" | make ARCH=$KARCH oldconfig > /dev/null &&
   cp .config "$OUTPUT/linux-fullconfig" &&

   # Build kernel. Copy config, device tree binary, and kernel binary to output
   make ARCH=$KARCH CROSS_COMPILE="$CROSS_COMPILE" -j $(nproc) all || exit 1
   [ -n "$DTB" ] && { cp "$DTB" "$OUTPUT/linux.dtb" || exit 1 ;}
   if [ -n "$MODULES" ]; then
     make ARCH=$KARCH INSTALL_MOD_PATH=modz modules_install &&
       (cd modz && find lib/modules | cpio -o -H newc $CPIO_OPTS ) | gzip \
        > "$OUTPUT/modules.cpio.gz" || exit 1
   fi
   cp "$VMLINUX" "$OUTPUT"/linux-kernel && cd .. && rm -rf linux && popd ||exit 1
 fi

 # clean up and package root filesystem for initramfs.
 if [ -z "$BUILTIN" ]; then
   announce initramfs
   { (cd "$ROOT" && find . | cpio -o -H newc $CPIO_OPTS ) || exit 1
     ! test -e "$OUTPUT/modules.cpio.gz" || zcat $_;} | gzip \
     > "$OUTPUT"/initramfs.cpio.gz || exit 1
 fi

 mv "$LOG/$CROSS".{n,y} && echo "Output is in $OUTPUT"
 rmdir "$TEMP" "$BUILD" 2>/dev/null || exit 0 # remove if empty, not an error
	#!/bin/bash

	# ------------------------------ Part 1: Setup -------------------------------

	# Clear environment variables by restarting script w/bare minimum passed through
	[ -z "$NOCLEAR" ] && exec env -i NOCLEAR=1 HOME="$HOME" PATH="$PATH" \
	LINUX="$LINUX" CROSS="$CROSS" CROSS_COMPILE="$CROSS_COMPILE" "$0" "$@"

	! [ -d mkroot ] && echo "Run mkroot/mkroot.sh from toybox source dir." && exit 1

	# assign command line NAME=VALUE args to env vars, the rest are packages
	for i in "$@"; do
	[ "${i/=/}" != "$i" ] && export "$i" \|\| { [ "$i" != -- ] && PKG="$PKG $i"; }
	done

	# Set default directory locations (overrideable from command line)
	: ${TOP:=$PWD/root} ${BUILD:=$TOP/build} ${LOG:=$BUILD/log}
	: ${AIRLOCK:=$BUILD/airlock} ${CCC:=$PWD/ccc} ${PKGDIR:=$PWD/mkroot/root}

	announce() { printf "\033]2;$CROSS $\007" >/dev/tty; printf "\n=== $\n";}
	die() { echo "$@" >&2; exit 1; }

	# ----- Are we cross compiling (via CROSS_COMPILE= or CROSS=)

	if [ -n "$CROSS_COMPILE" ]; then
	# airlock needs absolute path
	[ -z "${X:=$(command -v "$CROSS_COMPILE"cc)}" ] && die "no ${CROSS_COMPILE}cc"
	CROSS_COMPILE="$(realpath -s "${X%cc}")"
	[ -z "$CROSS" ] && CROSS=${CROSS_COMPILE/\//} CROSS=${CROSS/-/}

	elif [ -n "$CROSS" ]; then # CROSS=all/allnonstop/$ARCH else list known $ARCHes
	[ ! -d "$CCC" ] && die "No ccc symlink to compiler directory."
	TARGETS="$(ls "$CCC" \| sed -n 's/-.*//p' \| sort -u)"

	if [ "${CROSS::3}" == all ]; then # loop calling ourselves for each target
	for i in $TARGETS; do
	"$0" "$@" CROSS=$i \|\| [ "$CROSS" == allnonstop ] \|\| exit 1
	done; exit

	else # Find matching cross compiler under ccc/ else list available targets
	CROSS_COMPILE="$(echo "$CCC/$CROSS"-cross/bin/"$CROSS"-cc)" # wildcard
	[ ! -e "$CROSS_COMPILE" ] && echo $TARGETS && exit # list available targets
	CROSS_COMPILE="${CROSS_COMPILE%cc}" # trim to prefix for cc/ld/as/nm/strip
	fi
	fi

	# Set per-target output directory (using "host" if not cross-compiling)
	: ${CROSS:=host} ${OUTPUT:=$TOP/$CROSS}

	# Verify selected compiler works
	${CROSS_COMPILE}cc --static -xc - -o /dev/null <<< "int main(void){return 0;}"\|\|
	die "${CROSS_COMPILE}cc can't create static binaries"

	# ----- Create hermetic build environment

	if [ -z "$NOAIRLOCK"] && [ -n "$CROSS_COMPILE" ]; then
	# When cross compiling set host $PATH to binaries with known behavior by
	# - building a host toybox later builds use as their command line
	# - cherry-picking specific commands from old path via symlink
	if [ ! -e "$AIRLOCK/toybox" ]; then
	announce "airlock" &&
	PREFIX="$AIRLOCK" KCONFIG_CONFIG=.singleconfig_airlock CROSS_COMPILE= \
	make clean defconfig toybox install_airlock && # see scripts/install.sh
	rm .singleconfig_airlock \|\| exit 1
	fi
	export PATH="$AIRLOCK"
	CPIO_OPTS+=--no-preserve-owner
	fi

	# Create per-target work directories
	TEMP="$BUILD/${CROSS}-tmp" && rm -rf "$TEMP" &&
	mkdir -p "$TEMP" "$OUTPUT" "$LOG" \|\| exit 1
	[ -z "$ROOT" ] && ROOT="$OUTPUT/fs" && rm -rf "$ROOT"

	# ----- log build output

	# Install command line recording wrapper, logs all commands run from $PATH
	if [ -z "$NOLOGPATH" ]; then
	# Move cross compiler into $PATH so calls to it get logged
	[ -n "$CROSS_COMPILE" ] && PATH="${CROSS_COMPILE%/*}:$PATH" &&
	CROSS_COMPILE=${CROSS_COMPILE##*/}
	export WRAPDIR="$BUILD/record-commands" LOGPATH="$LOG/$CROSS-commands.txt"
	rm -rf "$WRAPDIR" "$LOGPATH" generated/obj &&
	WRAPDIR="$WRAPDIR" CROSS_COMPILE= NOSTRIP=1 source mkroot/record-commands \|\|
	exit 1
	fi

	# Start logging stdout/stderr
	rm -f "$LOG/$CROSS".{n,y} \|\| exit 1
	[ -z "$NOLOG" ] && exec > >(tee "$LOG/$CROSS.n") 2>&1
	echo "Building for $CROSS"

	# ---------------------- Part 2: Create root filesystem -----------------------

	# ----- Create new root filesystem's directory layout.

	# FHS wants boot media opt srv usr/{local,share}, stuff under /var...
	mkdir -p "$ROOT"/{dev,etc/rc,home,mnt,proc,root,sys,tmp/run,usr/{bin,sbin,lib},var} &&
	chmod a+rwxt "$ROOT"/tmp && ln -s usr/{bin,sbin,lib} tmp/run "$ROOT" \|\| exit 1

	# Write init script. Runs as pid 1 from initramfs to set up and hand off system.
	cat > "$ROOT"/init << 'EOF' &&
	#!/bin/sh

	export HOME=/home PATH=/bin:/sbin

	if ! mountpoint -q dev; then
	mount -t devtmpfs dev dev
	[ $$ -eq 1 ] && exec 0<>/dev/console 1>&0 2>&1
	for i in ,fd /0,stdin /1,stdout /2,stderr
	do ln -sf /proc/self/fd${i/,/} dev/${i/,/}; done
	mkdir -p dev/shm
	chmod +t /dev/shm
	fi
	mountpoint -q dev/pts \|\| { mkdir -p dev/pts && mount -t devpts dev/pts dev/pts;}
	mountpoint -q proc \|\| mount -t proc proc proc
	mountpoint -q sys \|\| mount -t sysfs sys sys
	echo 0 99999 > /proc/sys/net/ipv4/ping_group_range

	if [ $$ -eq 1 ]; then # Setup networking for QEMU (needs /proc)
	mountpoint -q mnt \|\| [ -e /dev/?da ] && mount /dev/?da /mnt
	ifconfig lo 127.0.0.1
	ifconfig eth0 10.0.2.15
	route add default gw 10.0.2.2
	[ "$(date +%s)" -lt 1000 ] && timeout 2 sntp -sq 10.0.2.2 # Ask host
	[ "$(date +%s)" -lt 10000000 ] && sntp -sq time.google.com

	# Run package scripts (if any)
	for i in $(ls -1 /etc/rc 2>/dev/null \| sort); do . /etc/rc/"$i"; done

	[ -z "$HANDOFF" ] && [ -e /mnt/init ] && HANDOFF=/mnt/init
	[ -z "$HANDOFF" ] && HANDOFF=/bin/sh && echo -e '\e[?7hType exit when done.'
	echo 3 > /proc/sys/kernel/printk
	exec oneit $HANDOFF
	else # for chroot
	/bin/sh
	umount /dev/pts /dev /sys /proc
	fi
	EOF
	chmod +x "$ROOT"/init &&

	# Google's nameserver, passwd+group with special (root/nobody) accounts + guest
	echo "nameserver 8.8.8.8" > "$ROOT"/etc/resolv.conf &&
	cat > "$ROOT"/etc/passwd << 'EOF' &&
	root:x:0:0:root:/root:/bin/sh
	guest:x:500:500:guest:/home/guest:/bin/sh
	nobody:x:65534:65534:nobody:/proc/self:/dev/null
	EOF
	echo -e 'root:x:0:\nguest:x:500:\nnobody:x:65534:' > "$ROOT"/etc/group \|\| exit 1

	# Build any packages listed on command line
	for i in ${PKG:+plumbing $PKG}; do
	pushd .
	announce "$i"; PATH="$PKGDIR:$PATH" source $i \|\| die $i
	popd
	done

	# Build static toybox with existing .config if there is one, else defconfig+sh
	announce toybox
	[ -n "$PENDING" ] && rm -f .config
	[ -e .config ] && CONF=silentoldconfig \|\| unset CONF
	for i in $PENDING sh route; do XX="$XX"$'\n'CONFIG_${i^^?}=y; done
	[ -e "$ROOT"/lib/libc.so ] \|\| export LDFLAGS=--static
	PREFIX="$ROOT" make clean \
	${CONF:-defconfig KCONFIG_ALLCONFIG=<(echo "$XX")} toybox install \|\| exit 1
	unset LDFLAGS

	# ------------------ Part 3: Build + package bootable system ------------------

	# Convert comma separated values in $1 to CONFIG=$2 lines
	csv2cfg() { sed -E '/^$/d;s/([^,]*)($\|,)/CONFIG_\1='"$2"'\n/g' <<< "$1"; }

	# ----- Build kernel for target

	if [ -z "$LINUX" ] \|\| [ ! -d "$LINUX/kernel" ]; then
	echo 'No $LINUX directory, kernel build skipped.'
	else
	# Which architecture are we building a kernel for?
	LINUX="$(realpath "$LINUX")"
	[ -z "$TARGET" ] &&
	{ [ "$CROSS" == host ] && TARGET="$(uname -m)" \|\| TARGET="$CROSS"; }

	# Target-specific info in an (alphabetical order) if/else staircase
	# Each target needs board config, serial console, RTC, ethernet, block device.

	if [ "$TARGET" == armv5l ]; then
	# This could use the same VIRT board as armv7, but let's demonstrate a
	# different one requiring a separate device tree binary.
	QEMU="arm -M versatilepb -net nic,model=rtl8139 -net user"
	KARCH=arm KARGS=ttyAMA0 VMLINUX=arch/arm/boot/zImage
	KCONF=CPU_ARM926T,MMU,VFP,ARM_THUMB,AEABI,ARCH_VERSATILE,ATAGS,DEPRECATED_PARAM_STRUCT,ARM_ATAG_DTB_COMPAT,ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND,SERIAL_AMBA_PL011,SERIAL_AMBA_PL011_CONSOLE,RTC_CLASS,RTC_DRV_PL031,RTC_HCTOSYS,PCI,PCI_VERSATILE,BLK_DEV_SD,SCSI,SCSI_LOWLEVEL,SCSI_SYM53C8XX_2,SCSI_SYM53C8XX_MMIO,NET_VENDOR_REALTEK,8139CP
	KERNEL_CONFIG="CONFIG_SCSI_SYM53C8XX_DMA_ADDRESSING_MODE=0"
	DTB=arch/arm/boot/dts/versatile-pb.dtb
	elif [ "$TARGET" == armv7l ] \|\| [ "$TARGET" == aarch64 ]; then
	if [ "$TARGET" == aarch64 ]; then
	QEMU="aarch64 -M virt -cpu cortex-a57"
	KARCH=arm64 VMLINUX=arch/arm64/boot/Image
	else
	QEMU="arm -M virt" KARCH=arm VMLINUX=arch/arm/boot/zImage
	fi
	KARGS=ttyAMA0
	KCONF=MMU,ARCH_MULTI_V7,ARCH_VIRT,SOC_DRA7XX,ARCH_OMAP2PLUS_TYPICAL,ARCH_ALPINE,ARM_THUMB,VDSO,CPU_IDLE,ARM_CPUIDLE,KERNEL_MODE_NEON,SERIAL_AMBA_PL011,SERIAL_AMBA_PL011_CONSOLE,RTC_CLASS,RTC_HCTOSYS,RTC_DRV_PL031,NET_CORE,VIRTIO_MENU,VIRTIO_NET,PCI,PCI_HOST_GENERIC,VIRTIO_BLK,VIRTIO_PCI,VIRTIO_MMIO,ATA,ATA_SFF,ATA_BMDMA,ATA_PIIX,PATA_PLATFORM,PATA_OF_PLATFORM,ATA_GENERIC,ARM_LPAE
	elif [ "$TARGET" == hexagon ]; then
	QEMU="hexagon -M comet" KARGS=ttyS0 VMLINUX=vmlinux
	KARCH="hexagon LLVM_IAS=1" KCONF=SPI,SPI_BITBANG,IOMMU_SUPPORT
	elif [ "$TARGET" == i486 ] \|\| [ "$TARGET" == i686 ] \|\|
	[ "$TARGET" == x86_64 ] \|\| [ "$TARGET" == x32 ]; then
	if [ "$TARGET" == i486 ]; then
	QEMU="i386 -cpu 486 -global fw_cfg.dma_enabled=false" KCONF=M486
	elif [ "$TARGET" == i686 ]; then
	QEMU="i386 -cpu pentium3" KCONF=MPENTIUMII
	else
	QEMU=x86_64 KCONF=64BIT
	[ "$TARGET" == x32 ] && KCONF=X86_X32
	fi
	KARCH=x86 KARGS=ttyS0 VMLINUX=arch/x86/boot/bzImage
	KCONF=$KCONF,UNWINDER_FRAME_POINTER,PCI,BLK_DEV_SD,ATA,ATA_SFF,ATA_BMDMA,ATA_PIIX,NET_VENDOR_INTEL,E1000,SERIAL_8250,SERIAL_8250_CONSOLE,RTC_CLASS
	elif [ "$TARGET" == m68k ]; then
	QEMU="m68k -M q800" KARCH=m68k KARGS=ttyS0 VMLINUX=vmlinux
	KCONF=MMU,M68040,M68KFPU_EMU,MAC,SCSI,SCSI_LOWLEVEL,BLK_DEV_SD,SCSI_MAC_ESP,MACINTOSH_DRIVERS,NET_CORE,NET_VENDOR_NATSEMI,MACSONIC,SERIAL_PMACZILOG,SERIAL_PMACZILOG_TTYS,SERIAL_PMACZILOG_CONSOLE
	elif [ "$TARGET" == mips ] \|\| [ "$TARGET" == mipsel ]; then
	QEMU="mips -M malta" KARCH=mips KARGS=ttyS0 VMLINUX=vmlinux
	KCONF=MIPS_MALTA,CPU_MIPS32_R2,SERIAL_8250,SERIAL_8250_CONSOLE,PCI,BLK_DEV_SD,ATA,ATA_SFF,ATA_BMDMA,ATA_PIIX,NET_VENDOR_AMD,PCNET32,POWER_RESET,POWER_RESET_SYSCON
	[ "$TARGET" == mipsel ] && KCONF=$KCONF,CPU_LITTLE_ENDIAN &&
	QEMU="mipsel -M malta"
	elif [ "$TARGET" == powerpc ]; then
	KARCH=powerpc QEMU="ppc -M g3beige" KARGS=ttyS0 VMLINUX=vmlinux
	KCONF=ALTIVEC,PPC_PMAC,PPC_OF_BOOT_TRAMPOLINE,ATA,ATA_SFF,ATA_BMDMA,PATA_MACIO,BLK_DEV_SD,MACINTOSH_DRIVERS,ADB,ADB_CUDA,NET_VENDOR_NATSEMI,NET_VENDOR_8390,NE2K_PCI,SERIO,SERIAL_PMACZILOG,SERIAL_PMACZILOG_TTYS,SERIAL_PMACZILOG_CONSOLE,BOOTX_TEXT
	elif [ "$TARGET" == powerpc64 ] \|\| [ "$TARGET" == powerpc64le ]; then
	KARCH=powerpc QEMU="ppc64 -M pseries -vga none" KARGS=hvc0
	VMLINUX=vmlinux
	KCONF=PPC64,PPC_PSERIES,PPC_OF_BOOT_TRAMPOLINE,BLK_DEV_SD,SCSI_LOWLEVEL,SCSI_IBMVSCSI,ATA,NET_VENDOR_IBM,IBMVETH,HVC_CONSOLE,PPC_TRANSACTIONAL_MEM,PPC_DISABLE_WERROR,SECTION_MISMATCH_WARN_ONLY
	[ "$TARGET" == powerpc64le ] && KCONF=$KCONF,CPU_LITTLE_ENDIAN
	elif [ "$TARGET" = s390x ]; then
	QEMU="s390x" KARCH=s390 VMLINUX=arch/s390/boot/bzImage
	KCONF=MARCH_Z900,PACK_STACK,NET_CORE,VIRTIO_NET,VIRTIO_BLK,SCLP_TTY,SCLP_CONSOLE,SCLP_VT220_TTY,SCLP_VT220_CONSOLE,S390_GUEST
	elif [ "$TARGET" == sh2eb ]; then
	BUILTIN=1 KARCH=sh VMLINUX=vmlinux
	KERNEL_CONFIG=$'CONFIG_MEMORY_START=0x10000000\nCONFIG_CMDLINE="console=ttyUL0 earlycon"'
	KCONF=CPU_SUBTYPE_J2,CPU_BIG_ENDIAN,SH_JCORE_SOC,SMP,BINFMT_ELF_FDPIC,JCORE_EMAC,SERIAL_UARTLITE,SERIAL_UARTLITE_CONSOLE,HZ_100,CMDLINE_OVERWRITE,SPI,SPI_JCORE,MMC,PWRSEQ_SIMPLE,MMC_BLOCK,MMC_SPI
	elif [ "$TARGET" == sh4 ]; then
	QEMU="sh4 -M r2d -serial null -serial mon:stdio" KARCH=sh
	KARGS="ttySC1 noiotrap" VMLINUX=arch/sh/boot/zImage
	KERNEL_CONFIG="CONFIG_MEMORY_START=0x0c000000"
	KCONF=CPU_SUBTYPE_SH7751R,MMU,VSYSCALL,SH_FPU,SH_RTS7751R2D,RTS7751R2D_PLUS,SERIAL_SH_SCI,SERIAL_SH_SCI_CONSOLE,PCI,NET_VENDOR_REALTEK,8139CP,PCI,BLK_DEV_SD,ATA,ATA_SFF,ATA_BMDMA,PATA_PLATFORM,BINFMT_ELF_FDPIC,BINFMT_FLAT
	#see also SPI SPI_SH_SCI MFD_SM501 RTC_CLASS RTC_DRV_R9701 RTC_DRV_SH RTC_HCTOSYS
	else die "Unknown \$TARGET $TARGET"
	fi

	# Write the qemu launch script
	if [ -n "$QEMU" ]; then
	[ -z "$BUILTIN" ] && INITRD="-initrd initramfs.cpio.gz"
	{ echo qemu-system-"$QEMU" '"$@"' $QEMU_MORE -nographic -no-reboot -m 256 \
	-kernel linux-kernel $INITRD ${DTB:+-dtb linux.dtb} \
	"-append \"panic=1 HOST=$TARGET console=$KARGS \$KARGS\"" &&
	echo "echo -e '\\e[?7h'"
	} > "$OUTPUT"/run-qemu.sh &&
	chmod +x "$OUTPUT"/run-qemu.sh \|\| exit 1
	fi

	announce "linux-$KARCH"
	pushd "$LINUX" && make distclean && popd &&
	cp -sfR "$LINUX" "$TEMP/linux" && pushd "$TEMP/linux" &&

	# Write linux-miniconfig
	{ echo "# make ARCH=$KARCH allnoconfig KCONFIG_ALLCONFIG=linux-miniconfig"
	echo -e "# make ARCH=$KARCH -j \$(nproc)\n# boot $VMLINUX\n\n"

	# Expand list of =y symbols, first generic then architecture-specific
	for i in BINFMT_ELF,BINFMT_SCRIPT,NO_HZ,HIGH_RES_TIMERS,BLK_DEV,BLK_DEV_INITRD,RD_GZIP,BLK_DEV_LOOP,EXT4_FS,EXT4_USE_FOR_EXT2,VFAT_FS,FAT_DEFAULT_UTF8,MISC_FILESYSTEMS,SQUASHFS,SQUASHFS_XATTR,SQUASHFS_ZLIB,DEVTMPFS,DEVTMPFS_MOUNT,TMPFS,TMPFS_POSIX_ACL,NET,PACKET,UNIX,INET,IPV6,NETDEVICES,NET_CORE,NETCONSOLE,ETHERNET,COMPAT_32BIT_TIME,EARLY_PRINTK,IKCONFIG,IKCONFIG_PROC $KCONF $KEXTRA ; do
	echo "# architecture ${X:-independent}"
	csv2cfg "$i" y
	X=specific
	done
	[ -n "$BUILTIN" ] && echo -e CONFIG_INITRAMFS_SOURCE="\"$OUTPUT/fs\""
	for i in $MODULES; do csv2cfg "$i" m; done
	echo "$KERNEL_CONFIG"
	} > "$OUTPUT/linux-miniconfig" &&
	make ARCH=$KARCH allnoconfig KCONFIG_ALLCONFIG="$OUTPUT/linux-miniconfig" &&

	# Second config pass to remove stupid kernel defaults
	# See http://lkml.iu.edu/hypermail/linux/kernel/1912.3/03493.html
	sed -e 's/# CONFIG_EXPERT .*/CONFIG_EXPERT=y/' -e "$(sed -E -e '/^$/d' \
	-e 's@([^,]*)($\|,)@/^CONFIG_\1=y/d;$a# CONFIG_\1 is not set\n@g' \
	<<< VT,SCHED_DEBUG,DEBUG_MISC,X86_DEBUG_FPU)" -i .config &&
	yes "" \| make ARCH=$KARCH oldconfig > /dev/null &&
	cp .config "$OUTPUT/linux-fullconfig" &&

	# Build kernel. Copy config, device tree binary, and kernel binary to output
	make ARCH=$KARCH CROSS_COMPILE="$CROSS_COMPILE" -j $(nproc) all \|\| exit 1
	[ -n "$DTB" ] && { cp "$DTB" "$OUTPUT/linux.dtb" \|\| exit 1 ;}
	if [ -n "$MODULES" ]; then
	make ARCH=$KARCH INSTALL_MOD_PATH=modz modules_install &&
	(cd modz && find lib/modules \| cpio -o -H newc $CPIO_OPTS ) \| gzip \
	> "$OUTPUT/modules.cpio.gz" \|\| exit 1
	fi
	cp "$VMLINUX" "$OUTPUT"/linux-kernel && cd .. && rm -rf linux && popd \|\|exit 1
	fi

	# clean up and package root filesystem for initramfs.
	if [ -z "$BUILTIN" ]; then
	announce initramfs
	{ (cd "$ROOT" && find . \| cpio -o -H newc $CPIO_OPTS ) \|\| exit 1
	! test -e "$OUTPUT/modules.cpio.gz" \|\| zcat $_;} \| gzip \
	> "$OUTPUT"/initramfs.cpio.gz \|\| exit 1
	fi

	mv "$LOG/$CROSS".{n,y} && echo "Output is in $OUTPUT"
	rmdir "$TEMP" "$BUILD" 2>/dev/null \|\| exit 0 # remove if empty, not an error