move initramfs extraction to separate script

.gitignore

@@ -1,2 +1,2 @@
 /data
-/test.bin
+/*.bin

build.sh

@@ -9,6 +9,7 @@ fi
 
 . ./patch_initramfs.sh
 . ./build_image.sh
+. ./shim_utils.sh
 
 print_help() {
   echo "Usage: ./build.sh output_path shim_path rootfs_dir"
@@ -55,34 +56,9 @@ mkdir $kernel_dir -p
 dd if=$kernel_loop of=$kernel_dir/kernel.bin bs=1M status=none
 
 echo "extracting data from kernel"
-previous_dir=$(pwd)
-cd $kernel_dir
-if [ -e "${kernel_dir}/binwalk.out" ]; then
-  #don't run binwalk again if we don't need to
-  binwalk_out=$(cat $kernel_dir/binwalk.out)
-else
-  binwalk_out=$(binwalk --extract kernel.bin --run-as=root)
-  echo $binwalk_out > $kernel_dir/binwalk.out
-fi
-#i can't be bothered to learn how to use sed
-extracted_file=$(echo $binwalk_out | pcregrep -o1 "\d+\s+0x([0-9A-F]+)\s+gzip compressed data")
-
-echo "extracting initramfs archive from kernel (this may take a while)"
-cd _kernel.bin.extracted/
-if [ ! -e "_${extracted_file}.extracted/" ]; then
-  binwalk --extract $extracted_file --run-as=root > /dev/null
-fi
-cd "_${extracted_file}.extracted/"
-cpio_file=$(file ./* | pcregrep -o1 "([0-9A-F]+):\s+ASCII cpio archive")
-
-echo "extracting initramfs cpio archive"
 initramfs_dir=/tmp/shim_initramfs
 rm -rf $initramfs_dir
-cat $cpio_file | cpio -D $initramfs_dir -imd --quiet
+extract_initramfs $kernel_dir/kernel.bin $kernel_dir $initramfs_dir
-echo "shim initramfs extracted to ${initramfs_dir}"
-
-#leave /tmp
-cd $previous_dir
 
 echo "patching initramfs"
 patch_initramfs $initramfs_dir

build_squashfs.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+#build a rootfs that uses a squashfs + unionfs
+#consists of a minimal busybox system containing:
+# - FUSE kernel modules from the shim
+# - unionfs-fuse statically compiled 
+# - the main squashfs, compressed with gzip
+
+
+#todo - gotta refactor the other build scripts first

shim_utils.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+#utilties for reading shim disk images
+
+extract_initramfs() {
+  local kernel_bin="$1"
+  local working_dir="$2"
+  local output_dir="$3"
+
+  #first stage
+  local kernel_file="$(basename $kernel_bin)"
+  local binwalk_out=$(binwalk --extract $kernel_bin --directory=$working_dir --run-as=root)
+  local stage1_file=$(echo $binwalk_out | pcregrep -o1 "\d+\s+0x([0-9A-F]+)\s+gzip compressed data")
+  local stage1_dir="$working_dir/_$kernel_file.extracted"
+  local stage1_path="$stage1_dir/$stage1_file"
+  
+  #second stage
+  binwalk --extract $stage1_path --directory=$stage1_dir --run-as=root
+  local stage2_dir="$stage1_dir/_$stage1_file.extracted/"
+  local cpio_file=$(file $stage2_dir/* | pcregrep -o1 "([0-9A-F]+):\s+ASCII cpio archive")
+  local cpio_path="$stage2_dir/$cpio_file"
+
+  rm -rf $output_dir
+  cat $cpio_path | cpio -D $output_dir -imd --quiet
+}