basic functionality
(THIS COMMIT WILL NOT BUILD) changelog: - builder will now apply rootfs to image - builder has basic functions to shrink image
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17
builder/lib/detect_arch.sh
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17
builder/lib/detect_arch.sh
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detect_arch() {
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LOOPDEV="$1"
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MNT_ROOT=$(mktemp -d)
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mount -o ro "${LOOPDEV}p3" "$MNT_ROOT"
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TARGET_ARCH=x86_64
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if [ -f "$MNT_ROOT/bin/bash" ]; then
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case "$(file -b "$MNT_ROOT/bin/bash" | awk -F ', ' '{print $2}' | tr '[:upper:]' '[:lower:]')" in
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# for now assume arm has aarch64 kernel
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*aarch64* | *armv8* | *arm*) TARGET_ARCH=arm64 ;;
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esac
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fi
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echo "$TARGET_ARCH"
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umount "$MNT_ROOT"
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rmdir "$MNT_ROOT"
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}
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106
builder/lib/extract_initramfs.sh
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106
builder/lib/extract_initramfs.sh
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#!/bin/bash
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#utilties for reading shim disk images
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run_binwalk() {
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if binwalk -h | grep -- '--run-as' >/dev/null; then
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binwalk "$@" --run-as=root
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else
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binwalk "$@"
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fi
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}
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#extract the initramfs from a kernel image
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extract_initramfs() {
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local kernel_bin="$1"
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local working_dir="$2"
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local output_dir="$3"
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#extract the compressed kernel image from the partition data
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local kernel_file="$(basename $kernel_bin)"
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local binwalk_out=$(run_binwalk --extract $kernel_bin --directory=$working_dir)
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local stage1_file=$(echo $binwalk_out | pcregrep -o1 "\d+\s+0x([0-9A-F]+)\s+gzip compressed data")
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local stage1_dir="$working_dir/_$kernel_file.extracted"
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local stage1_path="$stage1_dir/$stage1_file"
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#extract the initramfs cpio archive from the kernel image
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run_binwalk --extract $stage1_path --directory=$stage1_dir > /dev/null
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local stage2_dir="$stage1_dir/_$stage1_file.extracted/"
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local cpio_file=$(file $stage2_dir/* | pcregrep -o1 "([0-9A-F]+):\s+ASCII cpio archive")
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local cpio_path="$stage2_dir/$cpio_file"
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rm -rf $output_dir
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cat $cpio_path | cpio -D $output_dir -imd --quiet
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}
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extract_initramfs_arm() {
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local kernel_bin="$1"
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local working_dir="$2"
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local output_dir="$3"
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#extract the kernel lz4 archive from the partition
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local binwalk_out="$(run_binwalk $kernel_bin)"
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local lz4_offset="$(echo "$binwalk_out" | pcregrep -o1 "(\d+).+?LZ4 compressed data" | head -n1)"
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local lz4_file="$working_dir/kernel.lz4"
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local kernel_img="$working_dir/kernel_decompressed.bin"
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dd if=$kernel_bin of=$lz4_file iflag=skip_bytes,count_bytes skip=$lz4_offset status=none
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lz4 -d $lz4_file $kernel_img -q || true
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#extract the initramfs cpio archive from the kernel image
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local extracted_dir="$working_dir/_kernel_decompressed.bin.extracted"
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run_binwalk --extract $kernel_img --directory=$working_dir > /dev/null
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local cpio_file=$(file $extracted_dir/* | pcregrep -o1 "([0-9A-F]+):\s+ASCII cpio archive")
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local cpio_path="$extracted_dir/$cpio_file"
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rm -rf $output_dir
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cat $cpio_path | cpio -D $output_dir -imd --quiet
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}
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create_loop() {
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local loop_device=$(losetup -f)
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if [ ! -b "$loop_device" ]; then
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#we might run out of loop devices, see https://stackoverflow.com/a/66020349
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local major=$(grep loop /proc/devices | cut -c3)
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local number="$(echo "$loop_device" | grep -Eo '[0-9]+' | tail -n1)"
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mknod $loop_device b $major $number
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fi
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losetup -P $loop_device "${1}"
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echo $loop_device
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}
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copy_kernel() {
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local shim_path="$1"
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local kernel_dir="$2"
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local shim_loop=$(create_loop "${shim_path}")
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local kernel_loop="${shim_loop}p2" #KERN-A should always be p2
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dd if=$kernel_loop of=$kernel_dir/kernel.bin bs=1M status=none
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losetup -d $shim_loop
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}
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#copy the kernel image then extract the initramfs
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extract_initramfs_full() {
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local shim_path="$1"
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local rootfs_dir="$2"
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local kernel_bin="$3"
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local arch="$4"
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local kernel_dir=/tmp/shim_kernel
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echo "copying the shim kernel"
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rm -rf $kernel_dir
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mkdir $kernel_dir -p
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copy_kernel $shim_path $kernel_dir
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echo "extracting initramfs from kernel (this may take a while)"
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if [ "$arch" = "arm64" ]; then
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extract_initramfs_arm $kernel_dir/kernel.bin $kernel_dir $rootfs_dir
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else
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extract_initramfs $kernel_dir/kernel.bin $kernel_dir $rootfs_dir
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fi
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if [ "$kernel_bin" ]; then
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cp $kernel_dir/kernel.bin $kernel_bin
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fi
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rm -rf $kernel_dir
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}
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115
builder/lib/rootfs_utils.sh
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115
builder/lib/rootfs_utils.sh
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#!/bin/bash
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# Code was borrowed from the SH1mmer repo, credits to them
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# https://github.com/MercuryWorkshop/sh1mmer
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is_ext2() {
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local rootfs="$1"
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local offset="${2-0}"
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local sb_magic_offset=$((0x438))
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local sb_value=$(dd if="$rootfs" skip=$((offset + sb_magic_offset)) \
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count=2 bs=1 2>/dev/null)
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local expected_sb_value=$(printf '\123\357')
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if [ "$sb_value" = "$expected_sb_value" ]; then
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return 0
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fi
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return 1
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}
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enable_rw_mount() {
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local rootfs="$1"
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local offset="${2-0}"
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if ! is_ext2 "$rootfs" $offset; then
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echo "enable_rw_mount called on non-ext2 filesystem: $rootfs $offset" 1>&2
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return 1
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fi
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local ro_compat_offset=$((0x464 + 3))
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printf '\000' |
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dd of="$rootfs" seek=$((offset + ro_compat_offset)) \
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conv=notrunc count=1 bs=1 2>/dev/null
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}
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disable_rw_mount() {
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local rootfs="$1"
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local offset="${2-0}"
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if ! is_ext2 "$rootfs" $offset; then
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echo "disable_rw_mount called on non-ext2 filesystem: $rootfs $offset" 1>&2
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return 1
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fi
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local ro_compat_offset=$((0x464 + 3))
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printf '\377' |
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dd of="$rootfs" seek=$((offset + ro_compat_offset)) \
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conv=notrunc count=1 bs=1 2>/dev/null
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}
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shrink_partitions() {
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local shim="$1"
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fdisk "$shim" <<EOF
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d
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12
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d
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11
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d
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10
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d
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9
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d
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8
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d
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7
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d
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6
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d
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5
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d
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4
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d
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1
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p
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w
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EOF
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}
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truncate_image() {
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local buffer=35
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local sector_size=$("$SFDISK" -l "$1" | grep "Sector size" | awk '{print $4}')
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local final_sector=$(get_final_sector "$1")
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local end_bytes=$(((final_sector + buffer) * sector_size))
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log "Truncating image to $(format_bytes "$end_bytes")"
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truncate -s "$end_bytes" "$1"
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# recreate backup gpt table/header
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suppress sgdisk -e "$1" 2>&1 | sed 's/\a//g'
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}
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format_bytes() {
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numfmt --to=iec-i --suffix=B "$@"
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}
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shrink_root() {
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log "Shrinking ROOT-A Partition"
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enable_rw_mount "${LOOPDEV}p3"
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suppress e2fsck -fy "${LOOPDEV}p3"
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suppress resize2fs -M "${LOOPDEV}p3"
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disable_rw_mount "${LOOPDEV}p3"
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local sector_size=$(get_sector_size "$LOOPDEV")
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local block_size=$(tune2fs -l "${LOOPDEV}p3" | grep "Block size" | awk '{print $3}')
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local block_count=$(tune2fs -l "${LOOPDEV}p3" | grep "Block count" | awk '{print $3}')
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local original_sectors=$("$CGPT" show -i 3 -s -n -q "$LOOPDEV")
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local original_bytes=$((original_sectors * sector_size))
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local resized_bytes=$((block_count * block_size))
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local resized_sectors=$((resized_bytes / sector_size))
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echo "Resizing ROOT from $(format_bytes ${original_bytes}) to $(format_bytes ${resized_bytes})"
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"$CGPT" add -i 3 -s "$resized_sectors" "$LOOPDEV"
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partx -u -n 3 "$LOOPDEV"
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}
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69
builder/picoshim.sh
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69
builder/picoshim.sh
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#!/bin/bash
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# PicoShim Builder
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# 2024
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if [ $EUID -ne 0 ]; then
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echo "You MUST run this program with sudo or as root."
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exit 1
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fi
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if [ "$1" == "" ]; then
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echo "No shim passed, please pass a shim to the args."
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echo "$@"
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exit 1
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fi
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SCRIPT_DIR=$(dirname "$0")
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VERSION=1
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HOST_ARCH=$(lscpu | grep Architecture | awk '{print $2}')
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if [ $HOST_ARCH == "x86_64" ]; then
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CGPT="$SCRIPT_DIR/bins/cgpt.x86-64"
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SFDISK="$SCRIPT_DIR/bins/sfdisk.x86-64"
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else
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CGPT="$SCRIPT_DIR/bins/cgpt.aarch64"
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SFDISK="$SCRIPT_DIR/bins/sfdisk.aarch64"
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fi
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source lib/extract_initramfs.sh
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source lib/detect_arch.sh
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echo "PicoShim builder"
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echo "requires: binwalk, fdisk"
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SHIM="$1"
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initramfs="/tmp/initramfs_path"
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ROOTFS_MNT="/tmp/picoshim_rootmnt"
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loopdev=$(losetup -f)
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STATE_SIZE=$((1 * 1024 * 1024))
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rm -rf $initramfs # cleanup previous instances of picoshim, if they existed.
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mkdir -p $initramfs
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rm -rf $ROOTFS_MNT # cleanup previous instances of picoshim, if they existed.
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mkdir -p $ROOTFS_MNT
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if [ -f "$SHIM" ]; then
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losetup -P "$loopdev" "$SHIM"
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else
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exit 1
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fi
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arch=$(detect_arch $loopdev)
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extract_initramfs_full "$SHIM" "$initramfs" ""$loopdev"p2" "$arch"
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echo "creating new filesystem on rootfs"
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echo "y" | mkfs.ext4 "$loopdev"p3 -L ROOT-A
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echo "mounting & moving files from initramfs to rootfs"
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mount "$loopdev"p3 "$ROOTFS_MNT"
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mv "$initramfs"/* "$ROOTFS_MNT"/
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umount "$loopdev"p3
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shrink_root
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echo "cleaning up"
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losetup -D
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rm -rf $initramfs
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rm -rf $ROOTFS_MNT
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