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272 lines
10 KiB
272 lines
10 KiB
5 years ago
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#-------------------------------------------------------------------------------
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# elftools: dwarf/dwarf_expr.py
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#
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# Decoding DWARF expressions
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#
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# Eli Bendersky (eliben@gmail.com)
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# This code is in the public domain
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#-------------------------------------------------------------------------------
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from ..common.py3compat import BytesIO, iteritems
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from ..common.utils import struct_parse, bytelist2string
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# DWARF expression opcodes. name -> opcode mapping
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DW_OP_name2opcode = dict(
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DW_OP_addr=0x03,
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DW_OP_deref=0x06,
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DW_OP_const1u=0x08,
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DW_OP_const1s=0x09,
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DW_OP_const2u=0x0a,
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DW_OP_const2s=0x0b,
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DW_OP_const4u=0x0c,
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DW_OP_const4s=0x0d,
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DW_OP_const8u=0x0e,
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DW_OP_const8s=0x0f,
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DW_OP_constu=0x10,
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DW_OP_consts=0x11,
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DW_OP_dup=0x12,
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DW_OP_drop=0x13,
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DW_OP_over=0x14,
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DW_OP_pick=0x15,
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DW_OP_swap=0x16,
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DW_OP_rot=0x17,
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DW_OP_xderef=0x18,
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DW_OP_abs=0x19,
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DW_OP_and=0x1a,
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DW_OP_div=0x1b,
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DW_OP_minus=0x1c,
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DW_OP_mod=0x1d,
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DW_OP_mul=0x1e,
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DW_OP_neg=0x1f,
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DW_OP_not=0x20,
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DW_OP_or=0x21,
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DW_OP_plus=0x22,
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DW_OP_plus_uconst=0x23,
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DW_OP_shl=0x24,
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DW_OP_shr=0x25,
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DW_OP_shra=0x26,
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DW_OP_xor=0x27,
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DW_OP_bra=0x28,
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DW_OP_eq=0x29,
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DW_OP_ge=0x2a,
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DW_OP_gt=0x2b,
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DW_OP_le=0x2c,
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DW_OP_lt=0x2d,
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DW_OP_ne=0x2e,
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DW_OP_skip=0x2f,
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DW_OP_regx=0x90,
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DW_OP_fbreg=0x91,
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DW_OP_bregx=0x92,
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DW_OP_piece=0x93,
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DW_OP_deref_size=0x94,
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DW_OP_xderef_size=0x95,
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DW_OP_nop=0x96,
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DW_OP_push_object_address=0x97,
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DW_OP_call2=0x98,
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DW_OP_call4=0x99,
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DW_OP_call_ref=0x9a,
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DW_OP_form_tls_address=0x9b,
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DW_OP_call_frame_cfa=0x9c,
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DW_OP_bit_piece=0x9d,
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DW_OP_implicit_value=0x9e,
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DW_OP_stack_value=0x9f,
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DW_OP_implicit_pointer=0xa0,
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DW_OP_addrx=0xa1,
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DW_OP_constx=0xa2,
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DW_OP_entry_value=0xa3,
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DW_OP_const_type=0xa4,
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DW_OP_regval_type=0xa5,
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DW_OP_deref_type=0xa6,
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DW_OP_xderef_type=0xa7,
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DW_OP_convert=0xa8,
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DW_OP_reinterpret=0xa9,
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DW_OP_lo_user=0xe0,
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DW_OP_hi_user=0xff,
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)
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def _generate_dynamic_values(map, prefix, index_start, index_end, value_start):
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""" Generate values in a map (dict) dynamically. Each key starts with
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a (string) prefix, followed by an index in the inclusive range
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[index_start, index_end]. The values start at value_start.
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"""
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for index in range(index_start, index_end + 1):
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name = '%s%s' % (prefix, index)
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value = value_start + index - index_start
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map[name] = value
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_generate_dynamic_values(DW_OP_name2opcode, 'DW_OP_lit', 0, 31, 0x30)
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_generate_dynamic_values(DW_OP_name2opcode, 'DW_OP_reg', 0, 31, 0x50)
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_generate_dynamic_values(DW_OP_name2opcode, 'DW_OP_breg', 0, 31, 0x70)
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# opcode -> name mapping
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DW_OP_opcode2name = dict((v, k) for k, v in iteritems(DW_OP_name2opcode))
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class GenericExprVisitor(object):
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""" A DWARF expression is a sequence of instructions encoded in a block
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of bytes. This class decodes the sequence into discrete instructions
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with their arguments and allows generic "visiting" to process them.
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Usage: subclass this class, and override the needed methods. The
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easiest way would be to just override _after_visit, which gets passed
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each decoded instruction (with its arguments) in order. Clients of
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the visitor then just execute process_expr. The subclass can keep
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its own internal information updated in _after_visit and provide
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methods to extract it. For a good example of this usage, see the
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ExprDumper class in the descriptions module.
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A more complex usage could be to override visiting methods for
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specific instructions, by placing them into the dispatch table.
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"""
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def __init__(self, structs):
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self.structs = structs
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self._init_dispatch_table()
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self.stream = None
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self._cur_opcode = None
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self._cur_opcode_name = None
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self._cur_args = []
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def process_expr(self, expr):
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""" Process (visit) a DWARF expression. expr should be a list of
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(integer) byte values.
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"""
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self.stream = BytesIO(bytelist2string(expr))
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while True:
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# Get the next opcode from the stream. If nothing is left in the
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# stream, we're done.
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byte = self.stream.read(1)
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if len(byte) == 0:
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break
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# Decode the opcode and its name
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self._cur_opcode = ord(byte)
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self._cur_opcode_name = DW_OP_opcode2name.get(
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self._cur_opcode, 'OP:0x%x' % self._cur_opcode)
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# Will be filled in by visitors
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self._cur_args = []
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# Dispatch to a visitor function
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visitor = self._dispatch_table.get(
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self._cur_opcode,
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self._default_visitor)
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visitor(self._cur_opcode, self._cur_opcode_name)
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# Finally call the post-visit function
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self._after_visit(
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self._cur_opcode, self._cur_opcode_name, self._cur_args)
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def _after_visit(self, opcode, opcode_name, args):
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pass
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def _default_visitor(self, opcode, opcode_name):
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pass
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def _visit_OP_with_no_args(self, opcode, opcode_name):
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self._cur_args = []
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def _visit_OP_addr(self, opcode, opcode_name):
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self._cur_args = [
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struct_parse(self.structs.Dwarf_target_addr(''), self.stream)]
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def _make_visitor_arg_struct(self, struct_arg):
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""" Create a visitor method for an opcode that that accepts a single
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argument, specified by a struct.
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"""
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def visitor(opcode, opcode_name):
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self._cur_args = [struct_parse(struct_arg, self.stream)]
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return visitor
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def _make_visitor_arg_struct2(self, struct_arg1, struct_arg2):
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""" Create a visitor method for an opcode that that accepts two
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arguments, specified by structs.
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"""
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def visitor(opcode, opcode_name):
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self._cur_args = [
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struct_parse(struct_arg1, self.stream),
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struct_parse(struct_arg2, self.stream)]
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return visitor
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def _init_dispatch_table(self):
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self._dispatch_table = {}
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def add(opcode_name, func):
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self._dispatch_table[DW_OP_name2opcode[opcode_name]] = func
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add('DW_OP_addr', self._visit_OP_addr)
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add('DW_OP_const1u',
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self._make_visitor_arg_struct(self.structs.Dwarf_uint8('')))
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add('DW_OP_const1s',
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self._make_visitor_arg_struct(self.structs.Dwarf_int8('')))
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add('DW_OP_const2u',
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self._make_visitor_arg_struct(self.structs.Dwarf_uint16('')))
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add('DW_OP_const2s',
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self._make_visitor_arg_struct(self.structs.Dwarf_int16('')))
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add('DW_OP_const4u',
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self._make_visitor_arg_struct(self.structs.Dwarf_uint32('')))
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add('DW_OP_const4s',
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self._make_visitor_arg_struct(self.structs.Dwarf_int32('')))
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add('DW_OP_const8u',
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self._make_visitor_arg_struct2(
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self.structs.Dwarf_uint32(''),
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self.structs.Dwarf_uint32('')))
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add('DW_OP_const8s',
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self._make_visitor_arg_struct2(
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self.structs.Dwarf_int32(''),
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self.structs.Dwarf_int32('')))
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add('DW_OP_constu',
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self._make_visitor_arg_struct(self.structs.Dwarf_uleb128('')))
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add('DW_OP_consts',
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self._make_visitor_arg_struct(self.structs.Dwarf_sleb128('')))
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add('DW_OP_pick',
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self._make_visitor_arg_struct(self.structs.Dwarf_uint8('')))
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add('DW_OP_plus_uconst',
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self._make_visitor_arg_struct(self.structs.Dwarf_uleb128('')))
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add('DW_OP_bra',
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self._make_visitor_arg_struct(self.structs.Dwarf_int16('')))
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add('DW_OP_skip',
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self._make_visitor_arg_struct(self.structs.Dwarf_int16('')))
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for opname in [ 'DW_OP_deref', 'DW_OP_dup', 'DW_OP_drop', 'DW_OP_over',
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'DW_OP_swap', 'DW_OP_swap', 'DW_OP_rot', 'DW_OP_xderef',
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'DW_OP_abs', 'DW_OP_and', 'DW_OP_div', 'DW_OP_minus',
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'DW_OP_mod', 'DW_OP_mul', 'DW_OP_neg', 'DW_OP_not',
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'DW_OP_plus', 'DW_OP_shl', 'DW_OP_shr', 'DW_OP_shra',
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'DW_OP_xor', 'DW_OP_eq', 'DW_OP_ge', 'DW_OP_gt',
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'DW_OP_le', 'DW_OP_lt', 'DW_OP_ne', 'DW_OP_nop',
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'DW_OP_push_object_address', 'DW_OP_form_tls_address',
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'DW_OP_call_frame_cfa']:
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add(opname, self._visit_OP_with_no_args)
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for n in range(0, 32):
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add('DW_OP_lit%s' % n, self._visit_OP_with_no_args)
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add('DW_OP_reg%s' % n, self._visit_OP_with_no_args)
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add('DW_OP_breg%s' % n,
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self._make_visitor_arg_struct(self.structs.Dwarf_sleb128('')))
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add('DW_OP_fbreg',
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self._make_visitor_arg_struct(self.structs.Dwarf_sleb128('')))
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add('DW_OP_regx',
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self._make_visitor_arg_struct(self.structs.Dwarf_uleb128('')))
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add('DW_OP_bregx',
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self._make_visitor_arg_struct2(
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self.structs.Dwarf_uleb128(''),
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self.structs.Dwarf_sleb128('')))
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add('DW_OP_piece',
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self._make_visitor_arg_struct(self.structs.Dwarf_uleb128('')))
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add('DW_OP_bit_piece',
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self._make_visitor_arg_struct2(
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self.structs.Dwarf_uleb128(''),
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self.structs.Dwarf_uleb128('')))
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add('DW_OP_deref_size',
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self._make_visitor_arg_struct(self.structs.Dwarf_int8('')))
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add('DW_OP_xderef_size',
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self._make_visitor_arg_struct(self.structs.Dwarf_int8('')))
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add('DW_OP_call2',
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self._make_visitor_arg_struct(self.structs.Dwarf_uint16('')))
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add('DW_OP_call4',
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self._make_visitor_arg_struct(self.structs.Dwarf_uint32('')))
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add('DW_OP_call_ref',
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self._make_visitor_arg_struct(self.structs.Dwarf_offset('')))
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