#!/bin/bash

cat <<END_PATCH | arm-linux-gnueabi-as -mcpu=cortex-a9 -march=armv7-a -o _patch
MOV     R0, #0
MOV     R1, #0x64000000
ADD     R2, R1, #0x2800

memcpy:
CMP     R1, R2
LDRNE   R3, [R0],#4
STRNE   R3, [R1],#4
BNE     memcpy

LDMFD   SP!, {R0-R12,PC}
END_PATCH

arm-linux-gnueabi-objcopy -O binary _patch _patch.bin

FN=$1
OFFSET=$2
SIZE=$(stat -c %s $FN)
PATCHSIZE=$(stat -c %s _patch.bin)
PATCHED=$FN".patched"
JUMP=$(( (SIZE - OFFSET - PATCHSIZE - 8) / 4 )) 
JUMP=$(printf "%04X" $JUMP | sed 's/\(..\)\(..\)/\2\1/')

dd if=$FN ibs=1 count=$OFFSET of=$PATCHED 2>&-
echo $JUMP | xxd -r -p >> $PATCHED
echo "00EA" | xxd -r -p >> $PATCHED

dd if=$FN ibs=1 skip=$((OFFSET+4)) count=$((SIZE-PATCHSIZE-OFFSET-4)) of=$PATCHED oflag=append conv=notrunc 2>&-
cat _patch.bin >> $PATCHED

rm _patch _patch.bin