+platform_check_image_sdboot() {
+ local diskdev partdev diff
+
+ export_bootdevice && export_partdevice diskdev 0 || {
+ echo "Unable to determine upgrade device"
+ return 1
+ }
+
+ # get partitions table from boot device
+ get_partitions "/dev/$diskdev" bootdisk
+
+ # get partitions table from sysupgrade.bin
+ dd if="$1" of=/tmp/image.bs bs=512b count=1 > /dev/null 2>&1
+ sync
+ get_partitions /tmp/image.bs image
+
+ # compare tables
+ diff="$(grep -F -x -v -f /tmp/partmap.bootdisk /tmp/partmap.image)"
+
+ rm -f /tmp/image.bs /tmp/partmap.bootdisk /tmp/partmap.image
+
+ if [ -n "$diff" ]; then
+ echo "Partition layout has changed. Full image will be written."
+ ask_bool 0 "Abort" && exit 1
+ return 0
+ fi
+}
+platform_do_upgrade_sdboot() {
+ local diskdev partdev diff
+
+ export_bootdevice && export_partdevice diskdev 0 || {
+ echo "Unable to determine upgrade device"
+ return 1
+ }
+
+ if [ "$UPGRADE_OPT_SAVE_PARTITIONS" = "1" ]; then
+ # get partitions table from boot device
+ get_partitions "/dev/$diskdev" bootdisk
+
+ # get partitions table from sysupgrade.bin
+ dd if="$1" of=/tmp/image.bs bs=512b count=1 > /dev/null 2>&1
+ sync
+ get_partitions /tmp/image.bs image
+
+ # compare tables
+ diff="$(grep -F -x -v -f /tmp/partmap.bootdisk /tmp/partmap.image)"
+ else
+ diff=1
+ fi
+
+ if [ -n "$diff" ]; then
+ dd if="$1" of="/dev/$diskdev" bs=1024 count=4 > /dev/null 2>&1
+ dd if="$1" of="$diskdev" bs=1024 skip=4 seek=16384 > /dev/null 2>&1
+ sync
+
+ # Separate removal and addtion is necessary; otherwise, partition 1
+ # will be missing if it overlaps with the old partition 2
+ partx -d - "/dev/$diskdev"
+ partx -a - "/dev/$diskdev"
+
+ return 0
+ fi
+
+ # write kernel image
+ dd if="$1" of="$diskdev" bs=1024 skip=4 seek=16384 count=16384 > /dev/null 2>&1
+ sync
+
+ # iterate over each partition from the image and write it to the boot disk
+ while read part start size; do
+ if export_partdevice partdev $part; then
+ echo "Writing image to /dev/$partdev..."
+ dd if="$1" of="/dev/$partdev" bs=512 skip="$start" count="$size" > /dev/null 2>&1
+ sync
+ else
+ echo "Unable to find partition $part device, skipped."
+ fi
+ done < /tmp/partmap.image
+
+}