#------------------------------------------------------------------------------- # elftools: dwarf/dwarf_expr.py # # Decoding DWARF expressions # # Eli Bendersky (eliben@gmail.com) # This code is in the public domain #------------------------------------------------------------------------------- from collections import namedtuple from ..common.py3compat import BytesIO, iteritems from ..common.utils import struct_parse, bytelist2string, read_blob # DWARF expression opcodes. name -> opcode mapping DW_OP_name2opcode = dict( DW_OP_addr=0x03, DW_OP_deref=0x06, DW_OP_const1u=0x08, DW_OP_const1s=0x09, DW_OP_const2u=0x0a, DW_OP_const2s=0x0b, DW_OP_const4u=0x0c, DW_OP_const4s=0x0d, DW_OP_const8u=0x0e, DW_OP_const8s=0x0f, DW_OP_constu=0x10, DW_OP_consts=0x11, DW_OP_dup=0x12, DW_OP_drop=0x13, DW_OP_over=0x14, DW_OP_pick=0x15, DW_OP_swap=0x16, DW_OP_rot=0x17, DW_OP_xderef=0x18, DW_OP_abs=0x19, DW_OP_and=0x1a, DW_OP_div=0x1b, DW_OP_minus=0x1c, DW_OP_mod=0x1d, DW_OP_mul=0x1e, DW_OP_neg=0x1f, DW_OP_not=0x20, DW_OP_or=0x21, DW_OP_plus=0x22, DW_OP_plus_uconst=0x23, DW_OP_shl=0x24, DW_OP_shr=0x25, DW_OP_shra=0x26, DW_OP_xor=0x27, DW_OP_bra=0x28, DW_OP_eq=0x29, DW_OP_ge=0x2a, DW_OP_gt=0x2b, DW_OP_le=0x2c, DW_OP_lt=0x2d, DW_OP_ne=0x2e, DW_OP_skip=0x2f, DW_OP_regx=0x90, DW_OP_fbreg=0x91, DW_OP_bregx=0x92, DW_OP_piece=0x93, DW_OP_deref_size=0x94, DW_OP_xderef_size=0x95, DW_OP_nop=0x96, DW_OP_push_object_address=0x97, DW_OP_call2=0x98, DW_OP_call4=0x99, DW_OP_call_ref=0x9a, DW_OP_form_tls_address=0x9b, DW_OP_call_frame_cfa=0x9c, DW_OP_bit_piece=0x9d, DW_OP_implicit_value=0x9e, DW_OP_stack_value=0x9f, DW_OP_implicit_pointer=0xa0, DW_OP_addrx=0xa1, DW_OP_constx=0xa2, DW_OP_entry_value=0xa3, DW_OP_const_type=0xa4, DW_OP_regval_type=0xa5, DW_OP_deref_type=0xa6, DW_OP_xderef_type=0xa7, DW_OP_convert=0xa8, DW_OP_reinterpret=0xa9, DW_OP_lo_user=0xe0, DW_OP_GNU_push_tls_address=0xe0, DW_OP_GNU_implicit_pointer=0xf2, DW_OP_GNU_entry_value=0xf3, DW_OP_GNU_const_type=0xf4, DW_OP_GNU_regval_type=0xf5, DW_OP_GNU_deref_type=0xf6, DW_OP_GNU_convert=0xf7, DW_OP_GNU_parameter_ref=0xfa, DW_OP_hi_user=0xff, ) def _generate_dynamic_values(map, prefix, index_start, index_end, value_start): """ Generate values in a map (dict) dynamically. Each key starts with a (string) prefix, followed by an index in the inclusive range [index_start, index_end]. The values start at value_start. """ for index in range(index_start, index_end + 1): name = '%s%s' % (prefix, index) value = value_start + index - index_start map[name] = value _generate_dynamic_values(DW_OP_name2opcode, 'DW_OP_lit', 0, 31, 0x30) _generate_dynamic_values(DW_OP_name2opcode, 'DW_OP_reg', 0, 31, 0x50) _generate_dynamic_values(DW_OP_name2opcode, 'DW_OP_breg', 0, 31, 0x70) # opcode -> name mapping DW_OP_opcode2name = dict((v, k) for k, v in iteritems(DW_OP_name2opcode)) # Each parsed DWARF expression is returned as this type with its numeric opcode, # op name (as a string) and a list of arguments. DWARFExprOp = namedtuple('DWARFExprOp', 'op op_name args offset') class DWARFExprParser(object): """DWARF expression parser. When initialized, requires structs to cache a dispatch table. After that, parse_expr can be called repeatedly - it's stateless. """ def __init__(self, structs): self._dispatch_table = _init_dispatch_table(structs) def parse_expr(self, expr): """ Parses expr (a list of integers) into a list of DWARFExprOp. The list can potentially be nested. """ stream = BytesIO(bytelist2string(expr)) parsed = [] while True: # Get the next opcode from the stream. If nothing is left in the # stream, we're done. offset = stream.tell() byte = stream.read(1) if len(byte) == 0: break # Decode the opcode and its name. op = ord(byte) op_name = DW_OP_opcode2name.get(op, 'OP:0x%x' % op) # Use dispatch table to parse args. arg_parser = self._dispatch_table[op] args = arg_parser(stream) parsed.append(DWARFExprOp(op=op, op_name=op_name, args=args, offset=offset)) return parsed def _init_dispatch_table(structs): """Creates a dispatch table for parsing args of an op. Returns a dict mapping opcode to a function. The function accepts a stream and return a list of parsed arguments for the opcode from the stream; the stream is advanced by the function as needed. """ table = {} def add(opcode_name, func): table[DW_OP_name2opcode[opcode_name]] = func def parse_noargs(): return lambda stream: [] def parse_op_addr(): return lambda stream: [struct_parse(structs.Dwarf_target_addr(''), stream)] def parse_arg_struct(arg_struct): return lambda stream: [struct_parse(arg_struct, stream)] def parse_arg_struct2(arg1_struct, arg2_struct): return lambda stream: [struct_parse(arg1_struct, stream), struct_parse(arg2_struct, stream)] # ULEB128, then an expression of that length def parse_nestedexpr(): def parse(stream): size = struct_parse(structs.Dwarf_uleb128(''), stream) nested_expr_blob = read_blob(stream, size) return [DWARFExprParser(structs).parse_expr(nested_expr_blob)] return parse # ULEB128, then a blob of that size def parse_blob(): return lambda stream: [read_blob(stream, struct_parse(structs.Dwarf_uleb128(''), stream))] # ULEB128 with datatype DIE offset, then byte, then a blob of that size def parse_typedblob(): return lambda stream: [struct_parse(structs.Dwarf_uleb128(''), stream), read_blob(stream, struct_parse(structs.Dwarf_uint8(''), stream))] add('DW_OP_addr', parse_op_addr()) add('DW_OP_addrx', parse_arg_struct(structs.Dwarf_uleb128(''))) add('DW_OP_const1u', parse_arg_struct(structs.Dwarf_uint8(''))) add('DW_OP_const1s', parse_arg_struct(structs.Dwarf_int8(''))) add('DW_OP_const2u', parse_arg_struct(structs.Dwarf_uint16(''))) add('DW_OP_const2s', parse_arg_struct(structs.Dwarf_int16(''))) add('DW_OP_const4u', parse_arg_struct(structs.Dwarf_uint32(''))) add('DW_OP_const4s', parse_arg_struct(structs.Dwarf_int32(''))) add('DW_OP_const8u', parse_arg_struct(structs.Dwarf_uint64(''))) add('DW_OP_const8s', parse_arg_struct(structs.Dwarf_int64(''))) add('DW_OP_constu', parse_arg_struct(structs.Dwarf_uleb128(''))) add('DW_OP_consts', parse_arg_struct(structs.Dwarf_sleb128(''))) add('DW_OP_pick', parse_arg_struct(structs.Dwarf_uint8(''))) add('DW_OP_plus_uconst', parse_arg_struct(structs.Dwarf_uleb128(''))) add('DW_OP_bra', parse_arg_struct(structs.Dwarf_int16(''))) add('DW_OP_skip', parse_arg_struct(structs.Dwarf_int16(''))) for opname in [ 'DW_OP_deref', 'DW_OP_dup', 'DW_OP_drop', 'DW_OP_over', 'DW_OP_swap', 'DW_OP_swap', 'DW_OP_rot', 'DW_OP_xderef', 'DW_OP_abs', 'DW_OP_and', 'DW_OP_div', 'DW_OP_minus', 'DW_OP_mod', 'DW_OP_mul', 'DW_OP_neg', 'DW_OP_not', 'DW_OP_or', 'DW_OP_plus', 'DW_OP_shl', 'DW_OP_shr', 'DW_OP_shra', 'DW_OP_xor', 'DW_OP_eq', 'DW_OP_ge', 'DW_OP_gt', 'DW_OP_le', 'DW_OP_lt', 'DW_OP_ne', 'DW_OP_nop', 'DW_OP_push_object_address', 'DW_OP_form_tls_address', 'DW_OP_call_frame_cfa', 'DW_OP_stack_value', 'DW_OP_GNU_push_tls_address']: add(opname, parse_noargs()) for n in range(0, 32): add('DW_OP_lit%s' % n, parse_noargs()) add('DW_OP_reg%s' % n, parse_noargs()) add('DW_OP_breg%s' % n, parse_arg_struct(structs.Dwarf_sleb128(''))) add('DW_OP_fbreg', parse_arg_struct(structs.Dwarf_sleb128(''))) add('DW_OP_regx', parse_arg_struct(structs.Dwarf_uleb128(''))) add('DW_OP_bregx', parse_arg_struct2(structs.Dwarf_uleb128(''), structs.Dwarf_sleb128(''))) add('DW_OP_piece', parse_arg_struct(structs.Dwarf_uleb128(''))) add('DW_OP_bit_piece', parse_arg_struct2(structs.Dwarf_uleb128(''), structs.Dwarf_uleb128(''))) add('DW_OP_deref_size', parse_arg_struct(structs.Dwarf_int8(''))) add('DW_OP_xderef_size', parse_arg_struct(structs.Dwarf_int8(''))) add('DW_OP_call2', parse_arg_struct(structs.Dwarf_uint16(''))) add('DW_OP_call4', parse_arg_struct(structs.Dwarf_uint32(''))) add('DW_OP_call_ref', parse_arg_struct(structs.Dwarf_offset(''))) add('DW_OP_implicit_value', parse_blob()) add('DW_OP_entry_value', parse_nestedexpr()) add('DW_OP_const_type', parse_typedblob()) add('DW_OP_regval_type', parse_arg_struct2(structs.Dwarf_uleb128(''), structs.Dwarf_uleb128(''))) add('DW_OP_deref_type', parse_arg_struct2(structs.Dwarf_uint8(''), structs.Dwarf_uleb128(''))) add('DW_OP_implicit_pointer', parse_arg_struct2(structs.Dwarf_offset(''), structs.Dwarf_sleb128(''))) add('DW_OP_convert', parse_arg_struct(structs.Dwarf_uleb128(''))) add('DW_OP_GNU_entry_value', parse_nestedexpr()) add('DW_OP_GNU_const_type', parse_typedblob()) add('DW_OP_GNU_regval_type', parse_arg_struct2(structs.Dwarf_uleb128(''), structs.Dwarf_uleb128(''))) add('DW_OP_GNU_deref_type', parse_arg_struct2(structs.Dwarf_uint8(''), structs.Dwarf_uleb128(''))) add('DW_OP_GNU_implicit_pointer', parse_arg_struct2(structs.Dwarf_offset(''), structs.Dwarf_sleb128(''))) add('DW_OP_GNU_parameter_ref', parse_arg_struct(structs.Dwarf_offset(''))) add('DW_OP_GNU_convert', parse_arg_struct(structs.Dwarf_uleb128(''))) return table