Bash assembly emulator

asm.sh

function MMU_ERROR(){
	echo -e "MMU_PANIC: $1" >&2;
	while true;do 
		SPIN_FOREVER=1;
	done
	exit 1;
}

function JIT_ERROR(){
	echo -e "JIT Error: $1" >&2;
	exit 1;
}

function EMULATOR() {

	MEMORY_BASE=0x1000000
	MEMORY_END=0

	declare -a ARM64_GPREGS

	function ARM64_REG() {
		for REG in ${ARM64_GPREGS[@]};do
			if [[ "REG_$1" == "$REG" ]]; then
				return 0;
			fi
		done
		return 1;
	}

	function MEMORY_INIT() {

		echo "Initializing memory..." >&2;
		declare -a PAGEMAP
		
		function _ml_io_map() {
			PAGEMAP[$1]=0
		}

		echo "Setting up pages..." >&2;
		for addr in $(seq 0 1 $((0x4000))); do
			_ml_io_map $(( MEMORY_BASE + $(($addr)) ));
			MEMORY_END=$(( MEMORY_BASE + $(($addr)) ));
		done

		unset -f _ml_io_map

		echo "Memory initialized." >&2;
	}

	function PAGEFAULT(){
		printf "SEGMENTATION_FAULT: not paged %#llx\n" "$1" >&2;
	}

	function PAGECHECK() {
	
		MEMORY_BASE=0x1000000 # You cant fool me!
		
		# Do not modify the memory to be below the memory base you cant fool me
		if [ $(($MEMORY_END)) -lt $(($MEMORY_BASE)) ]; then
			MMU_ERROR "Don't hack the memory!"
		fi

		# Check if outside memory range
		if [ $(($1)) -lt $(($MEMORY_BASE)) ]; then
			PAGEFAULT $(($1));
			exit 1
		
		elif [ $(($1)) -gt $(($MEMORY_END)) ]; then
			PAGEFAULT $(($1));
			exit 1
		fi
		
	}

	# read at given address
	function MACHINE_READ(){
		PAGECHECK $(($1))		# Check if in pagemap
		echo ${PAGEMAP[$(($1))]};	# Read
	}

	function MACHINE_WRITE(){
		PAGECHECK $(($1))		# Check if in pagemap
		PAGEMAP[$(($1))]=$(($2));	# Write
	}

	# Get register value
	function CPU_GET_REG(){
		REG="REG_$1"
		VALUE="$(eval "echo \$$REG")"
		echo $(($VALUE))
	}

	# Set register value
	function CPU_SET_REG(){
		REG="REG_$1"
		VALUE="$2"
		eval "$REG=$(($VALUE))"
	}

	# MOV instruction
	function MOV() {

		DSTREG="$1"
		IMMEDIATE="$2"

		if ! ARM64_REG $DSTREG; then
			JIT_ERROR "Invalid destination register '$DSTREG'";
		fi

		if ARM64_REG $IMMEDIATE; then
			CPU_SET_REG $DSTREG $(CPU_GET_REG $IMMEDIATE)
		else
			CPU_SET_REG $DSTREG $(($IMMEDIATE))
		fi

	}

	# ADD instruction
	function ADD() {
	
		DSTREG="$1"
		IMMEDIATE_A="$2"
		IMMEDIATE_B="$3"

		if ! ARM64_REG $DSTREG; then
			JIT_ERROR "Invalid destination register '$DSTREG'";
		fi

		if ARM64_REG $IMMEDIATE_A; then
			CPU_SET_REG $DSTREG $(( $(CPU_GET_REG $IMMEDIATE_A) ))
		else
			CPU_SET_REG $DSTREG $(( $IMMEDIATE_A ))
		fi

		if ARM64_REG $IMMEDIATE_B; then
			CPU_SET_REG $DSTREG $(( $(( $(CPU_GET_REG $DSTREG) )) + $(($(CPU_GET_REG $IMMEDIATE_B))) ))
		else
			CPU_SET_REG $DSTREG $(( $(( $(CPU_GET_REG $DSTREG) )) + $(( $IMMEDIATE_B )) ))
		fi
	}

	# SUB instruction
	function SUB() {
		DSTREG="$1"
		IMMEDIATE_A="$2"
		IMMEDIATE_B="$3"

		if ! ARM64_REG $DSTREG; then
			JIT_ERROR "Invalid destination register '$DSTREG'";
		fi

		if ARM64_REG $IMMEDIATE_A; then
			CPU_SET_REG $DSTREG $(( $(CPU_GET_REG $IMMEDIATE_A) ))
		else
			CPU_SET_REG $DSTREG $(( $IMMEDIATE_A ))
		fi

		if ARM64_REG $IMMEDIATE_B; then
			CPU_SET_REG $DSTREG $(( $(( $(CPU_GET_REG $DSTREG) )) - $(($(CPU_GET_REG $IMMEDIATE_B))) ))
		else
			CPU_SET_REG $DSTREG $(( $(( $(CPU_GET_REG $DSTREG) )) - $(( $IMMEDIATE_B )) ))
		fi
	}

	# LDR instruction
	function LDR() {

		DSTREG="$1"
		SRCREG="$2"

		if ! ARM64_REG $DSTREG; then
			JIT_ERROR "Invalid destination register '$DSTREG'";
		fi

		if ! ARM64_REG $SRCREG; then
			JIT_ERROR "Invalid destination register '$SRCREG'";
		fi

		VALUE=$(($(MACHINE_READ $(CPU_GET_REG $SRCREG))))
		CPU_SET_REG $DSTREG $VALUE
	}

	function STR() {
		DSTREG="$1"
		SRCREG="$2"

		if ! ARM64_REG $DSTREG; then
			JIT_ERROR "Invalid destination register '$DSTREG'";
		fi

		if ! ARM64_REG $SRCREG; then
			JIT_ERROR "Invalid destination register '$SRCREG'";
		fi

		ADDR=$(($(CPU_GET_REG $DSTREG)))
		VALUE=$(($(CPU_GET_REG $SRCREG)))
		MACHINE_WRITE $ADDR $VALUE
	}

	function BL() {
		return 0;
	}

	# Branch instruction
	function B() {
		return 0;
	}

	# Debug instruction for printing regs
	function PRINT_REG() {
		printf "%d / %#llx\n" "$(CPU_GET_REG $1)" "$(CPU_GET_REG $1)"
	}

	# CPU Initialization
	function CPU_INIT() {
	
		echo "Initializing CPU..."
		declare -i ARM64_FLAGREG		# Condition flag register
	
		# Create and intialize general purpose registers
		for i in $(seq 0 1 31);do
			ARM64_GPREGS+="REG_X$i "
			declare -i "REG_X$i";
			eval REG_X$i[$i]=0;
		done
		
		echo "CPU initialized."
		return 0;
	}

	# Initialize CPU and memory
	CPU_INIT
	MEMORY_INIT

	# Undefine the init functions again
	unset -f CPU_INIT
	unset -f MEMORY_INIT

	# Start the interpreter
	while true;do 
		echo -e ">>> " | tr -d '\n'
		read ASM
		eval "$ASM"
	done
	
	return 0;
}

EMULATOR