scripts/pad_image

   1 #!/usr/bin/env bash
   2
   3 function usage {
   4   echo "Usage: prepare_image image_type kernel_image rootfs_image header_size"
   5   echo "Padd root and kernel image to the correct size and append the jffs2 start marker as needed"
   6   exit 1
   7 }
   8
   9 function pad_file {
  10         echo "Padding $1 to size $2"
  11         dd if=$1 of=$1.paddingtempfile bs=$2 count=1 conv=sync &> /dev/null
  12         mv $1.paddingtempfile $1
  13 }
  14
  15 #filesize filestart padding
  16 function calc_pad {
  17         [  $((($1 + $2) & ($3 - 1))) == 0 ] && {
  18                 echo $1
  19                 return 0
  20         }
  21         echo $(((($1 + $2) | ($3 - 1)) + 1 - $2))
  22 }
  23
  24 function prep_squash {
  25         echo "kernel_size: $kernel_size"
  26         echo "header_size: $header_size"
  27         kernel_pad_size=$(calc_pad $kernel_size $header_size 32)
  28         kernel_end=$(($header_size + $kernel_pad_size))
  29         pad_file $kernel_image $kernel_pad_size
  30
  31         #4k
  32         rootfs_pad_size=$(calc_pad $rootfs_size $kernel_end 4096)
  33         pad_file $rootfs_image $rootfs_pad_size
  34         echo -ne '\xde\xad\xc0\xde' >> $rootfs_image
  35
  36         #8k
  37         rootfs_pad_size=$(calc_pad $rootfs_size $kernel_end 8192)
  38         [ $rootfs_pad_size == rootfs_old_padsize ] || {
  39                 pad_file $rootfs_image $rootfs_pad_size
  40                 rootfs_old_padsize=$rootfs_pad_size
  41                 echo -ne '\xde\xad\xc0\xde' >> $rootfs_image
  42         }
  43
  44         #64k
  45         rootfs_pad_size=$(calc_pad $rootfs_size $kernel_end 65536)
  46         [ $rootfs_pad_size == rootfs_old_padsize ] || {
  47                 pad_file $rootfs_image $rootfs_pad_size
  48                 rootfs_old_padsize=$rootfs_pad_size
  49                 echo -ne '\xde\xad\xc0\xde' >> $rootfs_image
  50         }
  51
  52         #128k
  53         rootfs_pad_size=$(calc_pad $rootfs_size $kernel_end 131072)
  54         [ $rootfs_pad_size == rootfs_old_padsize ] || {
  55                 pad_file $rootfs_image $rootfs_pad_size
  56                 rootfs_old_padsize=$rootfs_pad_size
  57                 echo -ne '\xde\xad\xc0\xde' >> $rootfs_image
  58         }
  59
  60 }
  61
  62 function prep_jffs2 {
  63         kernel_pad_size=$(calc_pad $kernel_size $header_size $1)
  64         pad_file $kernel_image $kernel_pad_size
  65 }
  66
  67 image_type=$1
  68 kernel_image=$2
  69 rootfs_image=$3
  70 header_size=$4
  71
  72 if [ -z "$image_type" ] || [ -z "$rootfs_image" ] || [ -z "$kernel_image" ] || [ -z "$header_size" ]; then
  73         usage
  74 fi
  75
  76 if [ ! -e "$rootfs_image" ] || [ -z "$kernel_image" ]; then
  77         echo "input file not found"
  78         exit 1
  79 fi
  80
  81 kernel_size=$(stat -c "%s" "$kernel_image")
  82 rootfs_size=$(stat -c "%s" "$rootfs_image")
  83
  84 if [ $kernel_size == 0 ] || [ $rootfs_size == 0 ]; then
  85         echo "kernel or rootfs empty"
  86         exit 1
  87 fi
  88
  89 case $image_type in
  90         squashfs )
  91                 prep_squash ;;
  92         jffs2-64k )
  93                 prep_jffs2 65536 ;;
  94         jffs2-128k )
  95                 prep_jffs2 131072 ;;
  96         * )
  97                 echo "Unknown image type"
  98                 exit 1 ;;
  99 esac
 100