Fix factory installer for ARM platforms

factory_reset.sh

 #!/bin/sh -x
 
 # Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This runs from the factory install/reset shim. This MUST be run
 # from USB, in developer mode. This script will wipe OQC activity and
 # put the system back into factory fresh/shippable state.
 echo "Factory reset"
 
-# TODO: How do we know what this is for the general case?
-if [ -b /dev/sda ]; then
+# TODO(crosbug:10680): replace arch detection with crossystem?
+if uname -m | grep -q "^i.86\$"; then
+  ARCH="INTEL"
+elif [ $(uname -m ) = "x86_64" ]; then
+  ARCH="INTEL"
+elif [ $(uname -m ) = "armv7l" ]; then
+  ARCH="ARM"
+else
+  echo "Failed to auto detect architecture"
+  exit 1
+fi
+
+if [ "$ARCH" = "INTEL" ]; then
   STATE_DEV="/dev/sda1"
-elif [ -b /dev/mmcblk0 ]; then
-  STATE_DEV="/dev/mmcblk01"
+elif [ "$ARCH" = "ARM" ]; then
+  STATE_DEV="/dev/mmcblk0p1"
 else
+  STATE_DEV=""
+fi
+if [ ! -b "$STATE_DEV" ]; then
   echo "Failed to find root SSD."
   exit 1
 fi
 
 # Tcsd will bring up the tpm and de-own it,
 # as we are in developer/recovery mode.
 start tcsd
 
 # Just wipe the start of the partition and remake the fs on
 # the stateful partition.
 dd bs=4M count=1 if=/dev/zero of=${STATE_DEV}
 /sbin/mkfs.ext3 "$STATE_DEV"
 
 # Do any board specific resetting here.
 # board_factory_reset.sh will be installed by the board overlay if necessary.
 BOARD_RESET=/usr/sbin/board_factory_reset.sh
 if [ -x "${BOARD_RESET}" ]; then
   echo "Running board specific factory reset: ${BOARD_RESET}"
   ${BOARD_RESET} || exit 1
 fi
 
 echo "Done"