peda-arm.py

#
#       PEDA - Python Exploit Development Assistance for GDB
#
#       Copyright (C) 2012 Long Le Dinh <longld at vnsecurity.net>
#
#       License: see LICENSE file for details
#

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import os
import random
import sys

# point to absolute path of peda.py
PEDAFILE = os.path.abspath(os.path.expanduser(__file__))
while os.path.islink(PEDAFILE):
    PEDAFILE = os.path.abspath(os.path.join(os.path.dirname(PEDAFILE), os.path.expanduser(os.readlink(PEDAFILE))))
sys.path.insert(0, os.path.dirname(PEDAFILE))

from peda import *

try:
    import zlib
except ImportError:
    zlib = None

__version__ = 'alpha-1.0'


class Asm:
    """
    Wrapper class for assemble/disassemble using as
    """

    def __init__(self):
        # Check cross compile toolchains
        PREFIXES = "arm-none-eabi- arm-eabi- arm-androideabi- arm-none-linux-gnueabi- arm-linux-androideabi- " \
                   "arm-linux-android- arm-linux-eabi- arm-linux-gnueabi- arm-linux-gnueabihf-"
        prefix = ''
        for i in PREFIXES.split():
            command = "%sobjdump" % i
            if which(command):
                prefix = i
                break
        if prefix == '':
            warning('Cross compile toolchain not found! '
                    'You can install it from https://developer.arm.com/open-source/gnu-toolchain/gnu-rm/downloads')
            return

        self.PREFIX = prefix
        self.READELF = "%sreadelf" % prefix
        self.OBJDUMP = "%sobjdump" % prefix
        self.OBJCOPY = '%sobjcopy' % prefix
        self.AS = '%sas' % prefix

    def assemble(self, asmcode, arch='arm'):
        """
        Assemble ASM instructions using AS
            - asmcode: input ASM instructions, multiple instructions are separated by ";" (String)
            - arch: arm / aarch64 / thumb / thumb64 assembly

        Returns:
            - bin code (raw bytes)
        """
        if self.PREFIX == '':
            warning('Cross compile toolchain not found! ')
            return
        # todo aarch64 and thumb64
        gas = self.AS
        assemblers = {
            'arm': gas,
            'aarch64': '%s --64' % gas,
            'thumb': '%s -mthumb' % gas
        }
        arch = arch.lower()
        if '6' in arch:
            arch = 'aarch64'
        elif arch.startswith('t'):
            arch = 'thumb'
        else:
            arch = 'arm'
        assembler = assemblers[arch]

        asmcode = asmcode.strip('"').strip("'")
        asmcode = asmcode.replace(";", "\n")
        asmcode = decode_string_escape(asmcode)

        infd = tmpfile()
        elffd = tmpfile(is_binary_file=True)
        infd.write(asmcode)
        infd.flush()
        execute_external_command("%s -o %s %s" % (assembler, elffd.name, infd.name))
        infd.close()

        if not os.path.exists(elffd.name):
            # reopen it so tempfile will not complain
            open(elffd.name, 'w').write('B00B')
            return None

        outfd = tmpfile(is_binary_file=True)
        objcopy = '%s -j .text -Obinary %s %s' % (self.OBJCOPY, elffd.name, outfd.name)
        execute_external_command(objcopy)
        elffd.close()
        if not os.path.exists(outfd.name):
            # reopen it so tempfile will not complain
            open(outfd.name, 'w').write('B00B')
            return None
        bincode = outfd.read()
        outfd.close()
        return bincode

    def disassemble(self, buf, arch='arm'):
        """
        Disassemble binary to ASM instructions using OBJCOPY OBJDUMP
            - buf: input binary (raw bytes)
            - arch: arm / aarch64 / thumb / thumb64 assembly

        Returns:
            - ASM code (String)
        """
        if self.PREFIX == '':
            warning('Cross compile toolchain not found! ')
            return
        # todo aarch64 and thumb64
        if not buf:
            return None

        rawfd = tmpfile(is_binary_file=True)
        elffd = tmpfile(is_binary_file=True)

        objdump = [self.OBJDUMP, '-d', '--adjust-vma', '0', '-b', 'elf32-littlearm']
        objcopy = [self.OBJCOPY,
                   '-I', 'binary',
                   '-O', 'elf32-littlearm',
                   '-B', 'arm',
                   '--set-section-flags', '.data=code',
                   '--rename-section', '.data=.text',
                   ]

        if 'thumb' in arch:
            objcopy += ['--prefix-symbol=\\$t.']
        else:
            objcopy += ['-w', '-N', '\\*']

        rawfd.write(buf)
        rawfd.flush()

        execute_external_command(' '.join(objcopy + [rawfd.name, elffd.name]))
        out = execute_external_command(' '.join(objdump + [elffd.name]))
        out = out.split('<.text>:\n')

        if len(out) != 2:
            return None

        result = out[1].strip('\n').rstrip().expandtabs()
        return result

    def format_shellcode(self, buf, arch='arm'):
        """
        Format raw shellcode to disasm output display
            "\x6a\x01"  # 0x00000000:    push byte +0x1
            "\x5b"      # 0x00000002:    pop ebx

        TODO: understand syscall numbers, socket call
        """
        if self.PREFIX == '':
            warning('Cross compile toolchain not found! ')
            return
        asmcode = self.disassemble(buf, arch)

        if not asmcode:
            return ""

        shellcode = []
        # '   0:   e49df004        pop     {pc}            ; (ldr pc, [sp], #4)'
        pattern = re.compile(r"\s*([0-9a-f]+):\s*([0-9a-f]+)(.+)")

        # matches = pattern.findall(asmcode)
        for line in asmcode.splitlines():
            m = pattern.match(line)
            if m:
                (addr, bytes, code) = m.groups()
                sc = '"0x%s"' % bytes
                shellcode += [(sc, "0x" + addr, code.strip())]


# Define syscall dict {number:[function_name,name,params_num,[params...]]}
SYSTEM_CALLS = None

# Define registers
# REGISTERS = {
#     32: ['r' + str(i) for i in range(13)] + 'sp lr pc'.split(),
#     64: ['x' + str(i) for i in range(31)] + 'sp pc'.split()
# }

CPSRS = {
    32: 'N Z C V I F T'.split(),
    64: 'N Z C V SS IL D A I F'.split()
}

CPSR_TEXTS = {
    32: 'negative zero carry overflow no-irq no-fiq thumb'.split(),
    64: 'negative zero carry overflow software-step illegal-execution debug asynchronous-abort no-irq no-fiq'.split()
}

CPSR_N = 1 << 31
CPSR_Z = 1 << 30
CPSR_C = 1 << 29
CPSR_V = 1 << 28
CPSR_SS = 1 << 21
CPSR_IL = 1 << 20
CPSR_D = 1 << 9
CPSR_A = 1 << 8
CPSR_I = 1 << 7
CPSR_F = 1 << 6
CPSR_T = 1 << 5
CPSR_MASKS = {
    32: [CPSR_N, CPSR_Z, CPSR_C, CPSR_V, CPSR_I, CPSR_F, CPSR_T],
    64: [CPSR_N, CPSR_Z, CPSR_C, CPSR_V, CPSR_SS, CPSR_IL, CPSR_D, CPSR_A, CPSR_I, CPSR_F]
}

CPSR_M_MASKS = {
    32: 0b11111,
    64: 0b1111
}
CPSR_M_MODES = {
    32: {0b10000: 'user', 0b10001: 'fiq', 0b10010: 'irq', 0b10011: 'supervisor', 0b10111: 'abort', 0b11011: 'undefined',
         0b11111: 'system'},
    64: {0b0000: 'EL0t', 0b0100: 'El1t', 0b0101: 'EL1h', 0b1000: 'EL2t', 0b1001: 'EL2h', 0b1100: 'EL3t', 0b1101: 'EL3h'}
}


# CPSR = ["T", "F", "I", "V", "C", "Z", "N"]
# CPSR_TEXT = ["thumb", "no-fiq", "no-irq", "overflow", "carry", "zero", "negative"]
#
# CPSR_INDEX = [CPSR_T, CPSR_F, CPSR_I, CPSR_V, CPSR_C, CPSR_Z, CPSR_N]
# CPSR_M = 0b11111
# CPSR_M_TEXT = ['user', 'fiq', 'irq', 'supervisor', 'abort', 'undefined', 'system']
# CPSR_M_INDEX = [0b10000, 0b10001, 0b10010, 0b10011, 0b10111, 0b11011, 0b11111]
# CPSR_MODES = dict(zip(CPSR_M_INDEX, CPSR_M_TEXT))


class ArmPEDACmd(PEDACmd):
    def _get_function_args_32(self, code, argc=None):
        """
        Guess the number of arguments passed to a function - arm
        """
        reg_order = ["r0", "r1", "r2", "r3"]

        if argc is None:
            # deal with regs
            p = re.compile(r":\s*(\S+)\s*(\w+),")
            matches = p.findall(code)
            m = [r for (_, r) in matches]

            args = []
            regs = self.peda.getregs()
            for arg in reg_order:
                if arg in m:
                    args.append(regs[arg])
                else:
                    break

            if len(args) < 4:
                return args

            else:
                argc = 0
                #  '0x8d08: str     r3, [sp, #20]'
                p = re.compile(":\s*str\s*\S+,\s*\[sp.*#(.*)\]")
                matches = p.findall(code)
                if matches:
                    l = len(matches)
                    for v in matches:
                        # if v.startswith("+"):
                        offset = to_int(v)
                        if offset is not None and (offset // 4) > l:
                            continue
                        argc += 1
                else:  # try with push style todo
                    argc = code.count("push")

                argc = min(argc, 6)
                if argc == 0:
                    return args

                sp = self.peda.getreg("sp")
                mem = self.peda.dumpmem(sp, sp + 4 * argc)
                for i in range(argc):
                    args += [struct.unpack("<L", mem[i * 4:(i + 1) * 4])[0]]

                return args

        elif to_int(argc) is None:
            return None
        else:
            argc = to_int(argc)
            args = []

            # deal with regs
            regs = self.peda.getregs()
            for reg in reg_order:
                if argc == 0:
                    break
                args.append(regs[reg])
                argc -= 1

            if argc == 0:
                return args

            # deal with mem
            sp = self.peda.getreg("sp")
            mem = self.peda.dumpmem(sp, sp + 4 * argc)
            for i in range(argc):
                args += [struct.unpack("<L", mem[i * 4:(i + 1) * 4])[0]]

            return args

    def _get_function_args_64(self, code, argc=None):
        """
        Guess the number of arguments passed to a function - x86_64
        """
        return []

    def _get_function_args(self, argc=None):
        """
        Get the guessed arguments passed to a function when stopped at a call instruction

        Args:
            - argc: force to get specific number of arguments (Int)

        Returns:
            - list of arguments (List)
        """

        args = []
        regs = self.peda.getregs()
        if regs is None:
            return []

        bits = self.peda.getbits()

        code = ""
        if argc is None:
            pc = self.peda.getpc()
            prev_insts = self.peda.prev_inst(pc, 12)
            if not prev_insts:
                return []
            for (addr, inst) in prev_insts[::-1]:
                if inst.strip().startswith('b'):
                    break
                code = "0x%x:%s\n" % (addr, inst) + code

        if bits == 32:
            args = self._get_function_args_32(code, argc)
        elif bits == 64:
            args = self._get_function_args_64(code, argc)

        return args

    # get_function_args()
    def dumpargs(self, *arg):
        """
        Display arguments passed to a function when stopped at a call instruction
        Usage:
            MYNAME [count]
                count: force to display "count args" instead of guessing
        """

        (count,) = normalize_argv(arg, 1)
        if not self._is_running():
            return

        args = self._get_function_args(count)
        if args:
            msg("Guessed arguments:")
            for (i, a) in enumerate(args):
                chain = peda.examine_mem_reference(a)
                msg("arg[%d]: %s" % (i, format_reference_chain(chain)))
        else:
            msg("No argument")

        return

    # return [function_name,name,params_num,[params...],[params_value...]]
    def _get_syscall_args(self, num=None):
        if self.peda.getbits() != 32:
            # todo
            return None
        regs = self.peda.getregs()
        if regs is None:
            return None
        r7 = to_int(num)
        if r7 is None:
            r7 = regs['r7']
        if r7 not in SYSTEM_CALLS:
            return None
        function_name, name, params_num, params = SYSTEM_CALLS[r7]
        args = []

        # deal with regs
        for reg in 'r0 r1 r2 r3 r4 r5 r6'.split():
            if params_num == 0:
                break
            args.append(regs[reg])
            params_num -= 1

        if params_num != 0:
            # deal with mem
            sp = self.peda.getreg("sp")
            mem = self.peda.dumpmem(sp, sp + 4 * params_num)
            for i in range(params_num):
                args += [struct.unpack("<L", mem[i * 4:(i + 1) * 4])[0]]

        return function_name, name, len(params), params, args

    def syscall(self, *arg):
        """
        Display information at a system call instruction
        Usage:
            MYNAME [num]
                nun: force to display "system call num" instead of figure out register r7
        """
        if SYSTEM_CALLS is None:
            return

        (num,) = normalize_argv(arg, 1)
        if not self._is_running():
            return

        args = self._get_syscall_args(num)
        if args:
            function_name, name, params_num, params, args = args
            text = [blue('System call:', 'bold'),
                    '        %s' % function_name,
                    blue('Description:', 'bold'),
                    '        %s' % name,
                    blue("Arguments:", 'bold')]
            if params_num == 0:
                text.append('        Argument None')
            else:
                for i in range(params_num):
                    chain = peda.examine_mem_reference(args[i])
                    text.append("        arg[%d]:(%s) %s" % (i, params[i], format_reference_chain(chain)))
            text = '\n'.join(text)
            msg(text)
        else:
            msg("    System call not found!")

        return

    def syscall_detail(self, *arg):
        """
        Display details at a system call instruction
        Usage:
            MYNAME num | syscall_name
                num: force to display "system call num" instead of figure out register r7
        """
        if SYSTEM_CALLS is None:
            return
        (num,) = normalize_argv(arg, 1)
        if num is None:
            self._missing_argument()
        if to_int(num) is not None:
            func_name = SYSTEM_CALLS[to_int(num)][0]
        else:
            func_name = num
        peda.execute('shell man 2 %s' % func_name)

    # wrapper for stepuntil("j")
    def nextjmp(self, *arg):
        """
        Step until next 'j*' instruction in specific memory range
        Usage:
            MYNAME [keyword] [mapname1,mapname2]
        """
        (keyword, mapname) = normalize_argv(arg, 2)
        if keyword:
            self.stepuntil("b.*%s" % keyword, mapname)
        else:
            self.stepuntil("b", mapname)

    def _testjump(self, inst=None):
        """
        Test if jump instruction is taken or not

        Returns:
            - (status, address of target jumped instruction)
        """

        flags = self._get_cpsr()
        if not flags:
            return None

        if not inst:
            pc = self.peda.getpc()
            inst = self.peda.execute_redirect("x/i 0x%x" % pc)
            if not inst:
                return None

        # inst='=> 0x8b84 <_start+40>:\tblxeq.n\t0xa3bc <__libc_start_main>'
        match = re.match(r'.*:\s+(b[l|x]{0,2})(\S{0}|\S{2})(\.w|\.n)?\s+', inst)
        next_addr = self.peda.eval_target(inst)
        if next_addr is None:
            next_addr = 0

        if not match:
            return None

        cond = match.group(2)
        if (
                cond == ''
        ) or (
                cond == 'al'
        ) or (
                cond == "eq" and flags["Z"]
        ) or (
                cond == "ne" and not flags["Z"]
        ) or (
                (cond == 'cs' or cond == 'hs') and flags['C']
        ) or (
                (cond == 'cc' or cond == 'lo') and not flags['C']
        ) or (
                cond == 'mi' and flags['N']
        ) or (
                cond == 'pl' and not flags['N']
        ) or (
                cond == 'vs' and flags['V']
        ) or (
                cond == 'vc' and not flags['V']
        ) or (
                cond == 'hi' and flags['C'] and not flags['Z']
        ) or (
                cond == 'ls' and (not flags['C'] or flags['Z'])
        ) or (
                cond == 'ge' and (flags['Z'] or flags['N'] == flags['V'])
        ) or (
                cond == 'lt' and not flags['Z'] and flags['N'] != flags['V']
        ) or (
                cond == 'gt' and not flags['Z'] and flags['N'] == flags['V']
        ) or (
                cond == 'le' and (flags['Z'] or flags['N'] != flags['V'])
        ):
            return next_addr
        else:
            return None

    def _testjump_cb(self, inst=None):
        """
        Test if jump instruction for `cb` is taken or not

        Returns:
            - (status, address of target jumped instruction)
        """

        flags = self._get_cpsr()
        if not flags:
            return None

        if not inst:
            pc = self.peda.getpc()
            inst = self.peda.execute_redirect("x/i 0x%x" % pc)
            if not inst:
                return None

        # inst='=> 0xaf130bd4:\tcbz\tr0, 0xaf130be4'
        match = re.match(r'.*:\s+cb(n?z)?\s+(\S+),\s*(\S+)', inst)
        if not match:
            return None
        cond, r, next_addr = match.groups()
        r = self.peda.parse_and_eval(r)
        r = to_int(r)
        if r is None:
            return None
        next_addr = self.peda.parse_and_eval(next_addr)
        next_addr = to_int(next_addr)
        if next_addr is None:
            next_addr = 0

        if (
                cond == 'z' and r == 0
        ) or (
                cond == 'nz' and r != 0
        ):
            return next_addr
        else:
            return None

    @msg.bufferize
    def context_code(self, *arg):
        """
        Display nearby disassembly at $PC of current execution context
        Usage:
            MYNAME [linecount]
        """
        (count,) = normalize_argv(arg, 1)

        if count is None:
            count = 8

        if not self._is_running():
            return

        peda = self.peda
        pc = peda.getpc()
        if peda.is_address(pc):
            inst = peda.get_disasm(pc)
        else:
            inst = None

        text = blue("[%s]" % "CODE".center(self.width, "-"))
        msg(text)
        if inst:  # valid $PC
            text = ""
            opcode = inst.split(":\t")[-1].split()[0]
            if opcode.startswith('b'):
                jumpto = self._testjump(inst)
                if jumpto:  # JUMP is taken
                    code = peda.disassemble_around(pc, count)
                    code = code.splitlines()
                    pc_idx = 999
                    for (idx, line) in enumerate(code):
                        if ("0x%x" % pc) in line.split(":")[0]:
                            pc_idx = idx
                        if idx <= pc_idx:
                            text += line + "\n"
                        else:
                            text += " | %s\n" % line.strip()
                    text = format_disasm_code_arm(text, pc) + "\n"
                    text += " |->"
                    if 'x' in opcode:
                        current_mode = peda.execute_redirect('show arm force-mode')
                        match = re.search(r'"(\S*)"', current_mode)
                        if match:
                            current_mode = match.group(1)
                        else:
                            current_mode = 'auto'
                        peda.execute_redirect('set arm force-mode %s' % ('thumb' if jumpto & 0x1 else 'arm'))
                        code = peda.get_disasm(jumpto, count // 2)
                        peda.execute_redirect('set arm force-mode %s' % current_mode)
                    else:
                        code = peda.get_disasm(jumpto, count // 2)
                    if not code:
                        code = "   Cannot evaluate jump destination\n"
                    code = code.splitlines()
                    text += red(code[0]) + "\n"
                    for line in code[1:]:
                        text += "       %s\n" % line.strip()
                    text += red("JUMP is taken".rjust(self.width))
                    msg(text.rstrip())
                    self.dumpargs()
                else:  # JUMP is NOT taken
                    text += format_disasm_code_arm(peda.disassemble_around(pc, count), pc)
                    text += "\n" + green("JUMP is NOT taken".rjust(self.width))
                    msg(text.rstrip())
            elif opcode.startswith('cb'):
                jumpto = self._testjump_cb(inst)
                if jumpto:  # JUMP is taken
                    code = peda.disassemble_around(pc, count)
                    code = code.splitlines()
                    pc_idx = 999
                    for (idx, line) in enumerate(code):
                        if ("0x%x" % pc) in line.split(":")[0]:
                            pc_idx = idx
                        if idx <= pc_idx:
                            text += line + "\n"
                        else:
                            text += " | %s\n" % line.strip()
                    text = format_disasm_code_arm(text, pc) + "\n"
                    text += " |->"
                    code = peda.get_disasm(jumpto, count // 2)
                    if not code:
                        code = "   Cannot evaluate jump destination\n"
                    code = code.splitlines()
                    text += red(code[0]) + "\n"
                    for line in code[1:]:
                        text += "       %s\n" % line.strip()
                    text += red("JUMP is taken".rjust(self.width))
                    msg(text.rstrip())
                else:  # JUMP is NOT taken
                    text += format_disasm_code_arm(peda.disassemble_around(pc, count), pc)
                    text += "\n" + green("JUMP is NOT taken".rjust(self.width))
                    msg(text.rstrip())
            # stopped at other instructions
            else:
                text += peda.disassemble_around(pc, count)
                msg(format_disasm_code_arm(text, pc))
                if 'svc' in opcode:
                    msg('')
                    self.syscall()
        else:  # invalid $PC
            msg("Invalid $PC address: 0x%x" % pc, "red")

        return

    def _get_cpsr(self):
        """
        Get flags value from CPSR register

        Returns:
            - dictionary of named flags
        """

        # need indeed
        cpsr = self.peda.getreg("cpsr")
        # if not cpsr:
        #    return None

        bits = self.peda.getbits()
        CPSR = CPSRS[bits]
        CPSR_MASK = CPSR_MASKS[bits]
        flags = {}
        for i in range(len(CPSR)):
            flags[CPSR[i]] = bool(cpsr & CPSR_MASK[i])
        return flags

    def _get_mode(self):
        cpsr = self.peda.getreg("cpsr")
        if not cpsr:
            return None
        bits = self.peda.getbits()
        mode = cpsr & CPSR_M_MASKS[bits]
        CPSR_MODES = CPSR_M_MODES[bits]
        if mode in CPSR_MODES:
            return CPSR_MODES[mode].upper()
        else:
            return None

    def _set_cpsr(self, flagname, value):
        """
        Set/clear/toggle value of a flag register

        Returns:
            - True if success (Bool)
        """

        #  like above
        cpsr = self._get_cpsr()
        if not cpsr:
            return False

        bits = self.peda.getbits()
        CPSR = CPSRS[bits]
        CPSR_TEXT = CPSR_TEXTS[bits]
        CPSR_MASK = CPSR_MASKS[bits]

        if flagname.upper() in CPSR:
            index = CPSR.index(flagname.upper())
        elif flagname.lower() in CPSR_TEXT:
            index = CPSR_TEXT.index(flagname.lower())
        else:
            return False

        if value is None or cpsr[CPSR[index]] != value:  # switch value
            reg_cpsr = self.peda.getreg("cpsr")
            reg_cpsr ^= CPSR_MASK[index]
            result = self.peda.execute("set $cpsr = 0x%x" % reg_cpsr)
            return result

        return True

    def cpsr(self, *arg):
        """
        Display/set/clear value of cpsr register
        Usage:
            MYNAME
            MYNAME [set|clear] flagname
            MYNAME [set|clear|toggle] flagname
        """

        (option, flagname) = normalize_argv(arg, 2)
        if not self._is_running():
            return

        if option and not flagname:
            self._missing_argument()

        if option is None:  # display cpsr
            bits = self.peda.getbits()
            CPSR = CPSRS[bits]
            CPSR_TEXT = CPSR_TEXTS[bits]

            text = []
            flags = self._get_cpsr()
            for (i, f) in enumerate(CPSR):
                if flags[f]:
                    text.append(red(CPSR_TEXT[i].upper(), "bold"))
                else:
                    text.append(green(CPSR_TEXT[i].lower()))
            text.append(blue("[%s-MODE]" % self._get_mode()))
            text = ' '.join(text)

            cpsr = peda.getreg("cpsr")
            msg("%s: 0x%x (%s)" % (green("CPSR"), cpsr, text))

        elif option == "set":
            self._set_cpsr(flagname.lower(), True)

        elif option == "clear":
            self._set_cpsr(flagname, False)

        elif option == 'toggle':
            self._set_cpsr(flagname, None)

    cpsr.options = ["set", "clear"]

    def xinfo(self, *arg):
        """
        Display detail information of address/registers
        Usage:
            MYNAME address
            MYNAME register [reg1 reg2]
        """

        (address, regname) = normalize_argv(arg, 2)
        if address is None:
            self._missing_argument()

        super(ArmPEDACmd, self).xinfo(*arg)
        if str(address).startswith("r"):
            if regname is None or "cpsr" in regname:
                self.cpsr()

    xinfo.options = ["register"]

    ###############################
    #   Exploit Helper Commands   #
    ###############################
    @memoized
    def _assemble(self, asmcode, arch=None):
        """
        Assemble ASM instructions using NASM
            - asmcode: input ASM instructions, multiple instructions are separated by ";" (String)

        Returns:
            - bin code (raw bytes)
        """
        if arch is None:
            bits = self.peda.getbits()
            arch = 'arm' if bits == 32 else 'aarch64'
        return asm.assemble(asmcode, arch)

    def assemble(self, *arg):
        """
        On the fly assemble and execute instructions using AS. Auto exec when changing instruction at pc.
        Usage:
            MYNAME [mode] [address]
                mode: arm / aarch64 / thumb / thumb64
        """
        (mode, address) = normalize_argv(arg, 2)

        exec_mode = write_mode = False
        if to_int(mode) is not None:
            address, mode = mode, None

        if mode is None:
            bits = self.peda.getbits()
            cpsr = self._get_cpsr()
            if not cpsr:
                error('Not attached. Need to specify a MODE!')
                mode = 'error'
            elif cpsr['T']:
                mode = 'thumb' if bits == 32 else 'thumb64'
            else:
                mode = 'arm' if bits == 32 else 'aarch64'
        if mode not in ('arm', 'aarch64', 'thumb', 'thumb64'):
            self._missing_argument()

        if self._is_running() and address == peda.getpc():
            write_mode = exec_mode = True

        if address is None:
            write_mode = exec_mode = False
        elif peda.is_address(address):
            write_mode = True

        if write_mode:
            msg('Instruction will be written to 0x%x. '
                'Command "set write on" can be used to patch the binary file.' % address)
        else:
            msg("Instructions will be written to stdout")

        msg('Type instructions (%s syntax), one or more per line separated by ";".' % red(mode.upper()))
        msg('End with a line saying just "end".')

        if not write_mode:
            address = 0xdeadbeef

        inst_list = []
        inst_code = b""
        # fetch instruction loop
        while True:
            try:
                inst = input("%s|0x%x> " % (mode, address))
            except EOFError:
                msg('')
                break
            if inst == "end":
                break
            if inst == "":
                continue
            bincode = self._assemble(inst, mode)
            if bincode is None:
                continue
            size = len(bincode)
            if size == 0:
                continue
            inst_list.append((size, bincode, inst))
            if write_mode:
                peda.writemem(address, bincode)
            # execute assembled code
            if exec_mode:
                peda.execute("stepi %d" % (inst.count(";") + 1))

            address += size
            inst_code += bincode
            msg('hexify: "%s"' % to_hexstr(bincode))

        text = asm.format_shellcode(b"".join([x[1] for x in inst_list]), mode)
        if text:
            msg("Assembled%s instructions:" % ("/Executed" if exec_mode else ""))
            msg(text)
            msg('hexify: "%s"' % to_hexstr(inst_code))

        return

    assemble.options = ['arm', 'thumb']


###########################################################################
# INITIALIZATION #
# global instances of PEDA() and PEDACmd() and Asm(). Maybe not global?
asm = peda = pedacmd = None

if __name__ == '__main__':
    info('Checking cross compile toolchains')
    asm = Asm()
    info('Init PEDA main section.')
    peda = PEDA()
    pedacmd = ArmPEDACmd(peda, PEDAFILE)
    pedacmd.help.__func__.options = pedacmd.commands  # XXX HACK

    # register "peda" command in gdb
    info('Registering commands.')
    pedaGDBCommand(peda, pedacmd)
    Alias("pead", "peda")  # just for auto correction

    # create aliases for subcommands
    for cmd in pedacmd.commands:
        func = getattr(pedacmd, cmd)
        func.__func__.__doc__ = func.__doc__.replace("MYNAME", cmd)
        if cmd not in ["help", "show", "set"]:
            pedacmd._alias(cmd, cmd, False)

    # custom hooks
    peda.define_user_command("hook-stop", "peda context")

    # custom command aliases, add any alias you want
    pedacmd._alias("phelp", "help")
    pedacmd._alias("pset", "set")
    pedacmd._alias("pshow", "show")
    pedacmd._alias("find", "searchmem")  # override gdb find command
    pedacmd._alias("stack", "telescope $sp")
    pedacmd._alias("viewmem", "telescope")
    pedacmd._alias("reg", "xinfo register")

    Alias("arm", "set arm force-mode arm")
    Alias("thumb", "set arm force-mode thumb")
    Alias("auto", "set arm force-mode auto")

    PEDA.execute("set prompt \001%s\002" % red("\002peda-arm > \001"))  # custom prompt

    # Check syscalls
    if zlib:
        info('Loading system calls.')
        with open(os.path.dirname(PEDAFILE) + '/peda/arm/system_calls', 'rb') as f:
            # {number:[function_name,name,params_num,[params...]]}
            SYSTEM_CALLS = pickle_loads(zlib.decompress(f.read()))
    else:
        warning('zlib module not supported. Syscall lookup is disabled.')

    # Check logos
    msg('')

    if zlib:
        with open(os.path.dirname(PEDAFILE) + '/peda/arm/logos', 'rb') as f:
            logos = pickle_loads(zlib.decompress(f.read()))
        msg(logos[random.randint(0, len(logos) - 1)], 'blue', 'bold')
        msg(__version__.rjust(random.randint(10, len(logos) + 10)), 'red')
    else:
        msg(('PEDA-ARM ' + __version__).rjust(random.randint(10, 50)), 'red')
    msg(os.linesep)