Identify and handle jump tables (#732)

tools/isledecomp/isledecomp/compare/asm/instgen.py

@@ -0,0 +1,235 @@
+"""Pre-parser for x86 instructions. Will identify data/jump tables used with
+switch statements and local jump/call destinations."""
+import re
+import bisect
+import struct
+from enum import Enum, auto
+from collections import namedtuple
+from typing import List, NamedTuple, Optional, Tuple, Union
+from capstone import Cs, CS_ARCH_X86, CS_MODE_32
+from .const import JUMP_MNEMONICS
+
+disassembler = Cs(CS_ARCH_X86, CS_MODE_32)
+
+DisasmLiteInst = namedtuple("DisasmLiteInst", "address, size, mnemonic, op_str")
+
+displacement_regex = re.compile(r".*\+ (0x[0-9a-f]+)\]")
+
+
+class SectionType(Enum):
+    CODE = auto()
+    DATA_TAB = auto()
+    ADDR_TAB = auto()
+
+
+class FuncSection(NamedTuple):
+    type: SectionType
+    contents: List[Union[DisasmLiteInst, Tuple[str, int]]]
+
+
+class InstructGen:
+    # pylint: disable=too-many-instance-attributes
+    def __init__(self, blob: bytes, start: int) -> None:
+        self.blob = blob
+        self.start = start
+        self.end = len(blob) + start
+        self.section_end: int = self.end
+        self.code_tracks: List[List[DisasmLiteInst]] = []
+
+        # Todo: Could be refactored later
+        self.cur_addr: int = 0
+        self.cur_section_type: SectionType = SectionType.CODE
+        self.section_start = start
+
+        self.sections: List[FuncSection] = []
+
+        self.confirmed_addrs = {}
+        self.analysis()
+
+    def _finish_section(self, type_: SectionType, stuff):
+        sect = FuncSection(type_, stuff)
+        self.sections.append(sect)
+
+    def _insert_confirmed_addr(self, addr: int, type_: SectionType):
+        # Ignore address outside the bounds of the function
+        if not self.start <= addr < self.end:
+            return
+
+        self.confirmed_addrs[addr] = type_
+
+        # This newly inserted address might signal the end of this section.
+        # For example, a jump table at the end of the function means we should
+        # stop reading instructions once we hit that address.
+        # However, if there is a jump table in between code sections, we might
+        # read a jump to an address back to the beginning of the function
+        # (e.g. a loop that spans the entire function)
+        # so ignore this address because we have already passed it.
+        if type_ != self.cur_section_type and addr > self.cur_addr:
+            self.section_end = min(self.section_end, addr)
+
+    def _next_section(self, addr: int) -> Optional[SectionType]:
+        """We have reached the start of a new section. Tell what kind of
+        data we are looking at (code or other) and how much we should read."""
+
+        # Assume the start of every function is code.
+        if addr == self.start:
+            self.section_end = self.end
+            return SectionType.CODE
+
+        # The start of a new section must be an address that we've seen.
+        new_type = self.confirmed_addrs.get(addr)
+        if new_type is None:
+            return None
+
+        self.cur_section_type = new_type
+
+        # The confirmed addrs dict is sorted by insertion order
+        # i.e. the order in which we read the addresses
+        # So we have to sort and then find the next item
+        # to see where this section should end.
+
+        # If we are in a CODE section, ignore contiguous CODE addresses.
+        # These are not the start of a new section.
+        # However: if we are not in CODE, any upcoming address is a new section.
+        # Do this so we can detect contiguous non-CODE sections.
+        confirmed = [
+            conf_addr
+            for (conf_addr, conf_type) in sorted(self.confirmed_addrs.items())
+            if self.cur_section_type != SectionType.CODE
+            or conf_type != self.cur_section_type
+        ]
+
+        index = bisect.bisect_right(confirmed, addr)
+        if index < len(confirmed):
+            self.section_end = confirmed[index]
+        else:
+            self.section_end = self.end
+
+        return new_type
+
+    def _get_code_for(self, addr: int) -> List[DisasmLiteInst]:
+        """Start disassembling at the given address."""
+        # If we are reading a code block beyond the first, see if we already
+        # have disassembled instructions beginning at the specified address.
+        # For a CODE/ADDR/CODE function, we might get lucky and produce the
+        # correct instruction after the jump table's junk instructions.
+        for track in self.code_tracks:
+            for i, inst in enumerate(track):
+                if inst.address == addr:
+                    return track[i:]
+
+        # If we are here, we don't have the instructions.
+        # Todo: Could try to be clever here and disassemble only
+        # as much as we probably need (i.e. if a jump table is between CODE
+        # blocks, there are probably only a few bad instructions after the
+        # jump table is finished. We could disassemble up to the next verified
+        # code address and stitch it together)
+
+        blob_cropped = self.blob[addr - self.start :]
+        instructions = [
+            DisasmLiteInst(*inst)
+            for inst in disassembler.disasm_lite(blob_cropped, addr)
+        ]
+        self.code_tracks.append(instructions)
+        return instructions
+
+    def _handle_jump(self, inst: DisasmLiteInst):
+        # If this is a regular jump and its destination is within the
+        # bounds of the binary data (i.e. presumed function size)
+        # add it to our list of confirmed addresses.
+        if inst.op_str[0] == "0":
+            value = int(inst.op_str, 16)
+            self._insert_confirmed_addr(value, SectionType.CODE)
+
+        # If this is jumping into a table of addresses, save the destination
+        elif (match := displacement_regex.match(inst.op_str)) is not None:
+            value = int(match.group(1), 16)
+            self._insert_confirmed_addr(value, SectionType.ADDR_TAB)
+
+    def analysis(self):
+        self.cur_addr = self.start
+
+        while (sect_type := self._next_section(self.cur_addr)) is not None:
+            self.section_start = self.cur_addr
+
+            if sect_type == SectionType.CODE:
+                instructions = self._get_code_for(self.cur_addr)
+
+                # If we didn't get any instructions back, something is wrong.
+                # i.e. We can only read part of the full instruction that is up next.
+                if len(instructions) == 0:
+                    # Nudge the current addr so we will eventually move on to the
+                    # next section.
+                    # Todo: Maybe we could just call it quits here
+                    self.cur_addr += 1
+                    break
+
+                for inst in instructions:
+                    # section_end is updated as we read instructions.
+                    # If we are into a jump/data table and would read
+                    # a junk instruction, stop here.
+                    if self.cur_addr >= self.section_end:
+                        break
+
+                    # print(f"{inst.address:x} : {inst.mnemonic} {inst.op_str}")
+
+                    if inst.mnemonic in JUMP_MNEMONICS:
+                        self._handle_jump(inst)
+                        # Todo: log calls too (unwind section)
+                    elif inst.mnemonic == "mov":
+                        # Todo: maintain pairing of data/jump tables
+                        if (match := displacement_regex.match(inst.op_str)) is not None:
+                            value = int(match.group(1), 16)
+                            self._insert_confirmed_addr(value, SectionType.DATA_TAB)
+
+                    # Do this instead of copying instruction address.
+                    # If there is only one instruction, we would get stuck here.
+                    self.cur_addr += inst.size
+
+                # End of for loop on instructions.
+                # We are at the end of the section or the entire function.
+                # Cut out only the valid instructions for this section
+                # and save it for later.
+
+                # Todo: don't need to iter on every instruction here.
+                # They are already in order.
+                instruction_slice = [
+                    inst for inst in instructions if inst.address < self.section_end
+                ]
+                self._finish_section(SectionType.CODE, instruction_slice)
+
+            elif sect_type == SectionType.ADDR_TAB:
+                # Clamp to multiple of 4 (dwords)
+                read_size = ((self.section_end - self.cur_addr) // 4) * 4
+                offsets = range(self.section_start, self.section_start + read_size, 4)
+                dwords = self.blob[
+                    self.cur_addr - self.start : self.cur_addr - self.start + read_size
+                ]
+                addrs = [addr for addr, in struct.iter_unpack("<L", dwords)]
+                for addr in addrs:
+                    # Todo: the fact that these are jump table destinations
+                    # should factor into the label name.
+                    self._insert_confirmed_addr(addr, SectionType.CODE)
+
+                jump_table = list(zip(offsets, addrs))
+                # for (t0,t1) in jump_table:
+                #     print(f"{t0:x} : --> {t1:x}")
+
+                self._finish_section(SectionType.ADDR_TAB, jump_table)
+                self.cur_addr = self.section_end
+
+            else:
+                # Todo: variable data size?
+                read_size = self.section_end - self.cur_addr
+                offsets = range(self.section_start, self.section_start + read_size)
+                bytes_ = self.blob[
+                    self.cur_addr - self.start : self.cur_addr - self.start + read_size
+                ]
+                data = [b for b, in struct.iter_unpack("<B", bytes_)]
+
+                data_table = list(zip(offsets, data))
+                # for (t0,t1) in data_table:
+                #     print(f"{t0:x} : value {t1:02x}")
+
+                self._finish_section(SectionType.DATA_TAB, data_table)
+                self.cur_addr = self.section_end

tools/isledecomp/isledecomp/compare/asm/parse.py

@@ -11,13 +11,13 @@
 from typing import Callable, List, Optional, Tuple
 from collections import namedtuple
 from isledecomp.bin import InvalidVirtualAddressError
-from capstone import Cs, CS_ARCH_X86, CS_MODE_32
 from .const import JUMP_MNEMONICS, SINGLE_OPERAND_INSTS
-
+from .instgen import InstructGen, SectionType
-disassembler = Cs(CS_ARCH_X86, CS_MODE_32)
 
 ptr_replace_regex = re.compile(r"\[(0x[0-9a-f]+)\]")
 
+displace_replace_regex = re.compile(r"\+ (0x[0-9a-f]+)\]")
+
 # For matching an immediate value on its own.
 # Preceded by start-of-string (first operand) or comma-space (second operand)
 immediate_replace_regex = re.compile(r"(?:^|, )(0x[0-9a-f]+)")
@@ -172,34 +172,52 @@ def sanitize(self, inst: DisasmLiteInst) -> Tuple[str, str]:
         else:
             op_str = ptr_replace_regex.sub(self.hex_replace_always, inst.op_str)
 
+            # We only want relocated addresses for pointer displacement.
+            # i.e. ptr [register + something]
+            # Otherwise we would use a placeholder for every stack variable,
+            # vtable call, or this->member access.
+            op_str = displace_replace_regex.sub(self.hex_replace_relocated, op_str)
+
         op_str = immediate_replace_regex.sub(self.hex_replace_relocated, op_str)
         return (inst.mnemonic, op_str)
 
     def parse_asm(self, data: bytes, start_addr: Optional[int] = 0) -> List[str]:
         asm = []
 
-        for raw_inst in disassembler.disasm_lite(data, start_addr):
+        ig = InstructGen(data, start_addr)
-            # Use heuristics to disregard some differences that aren't representative
-            # of the accuracy of a function (e.g. global offsets)
-            inst = DisasmLiteInst(*raw_inst)
 
-            # If there is no pointer or immediate value in the op_str,
+        for sect_type, sect_contents in ig.sections:
-            # there is nothing to sanitize.
+            if sect_type == SectionType.CODE:
-            # This leaves us with cases where a small immediate value or
+                for inst in sect_contents:
-            # small displacement (this.member or vtable calls) appears.
+                    # Use heuristics to disregard some differences that aren't representative
-            # If we assume that instructions we want to sanitize need to be 5
+                    # of the accuracy of a function (e.g. global offsets)
-            # bytes -- 1 for the opcode and 4 for the address -- exclude cases
-            # where the hex value could not be an address.
-            # The exception is jumps which are as small as 2 bytes
-            # but are still useful to sanitize.
-            if "0x" in inst.op_str and (
-                inst.mnemonic in JUMP_MNEMONICS or inst.size > 4
-            ):
-                result = self.sanitize(inst)
-            else:
-                result = (inst.mnemonic, inst.op_str)
 
-            # mnemonic + " " + op_str
+                    # If there is no pointer or immediate value in the op_str,
-            asm.append((hex(inst.address), " ".join(result)))
+                    # there is nothing to sanitize.
+                    # This leaves us with cases where a small immediate value or
+                    # small displacement (this.member or vtable calls) appears.
+                    # If we assume that instructions we want to sanitize need to be 5
+                    # bytes -- 1 for the opcode and 4 for the address -- exclude cases
+                    # where the hex value could not be an address.
+                    # The exception is jumps which are as small as 2 bytes
+                    # but are still useful to sanitize.
+                    if "0x" in inst.op_str and (
+                        inst.mnemonic in JUMP_MNEMONICS or inst.size > 4
+                    ):
+                        result = self.sanitize(inst)
+                    else:
+                        result = (inst.mnemonic, inst.op_str)
+
+                    # mnemonic + " " + op_str
+                    asm.append((hex(inst.address), " ".join(result)))
+            elif sect_type == SectionType.ADDR_TAB:
+                asm.append(("", "Jump table:"))
+                for i, (ofs, _) in enumerate(sect_contents):
+                    asm.append((hex(ofs), f"Jump_dest_{i}"))
+
+            elif sect_type == SectionType.DATA_TAB:
+                asm.append(("", "Data table:"))
+                for ofs, b in sect_contents:
+                    asm.append((hex(ofs), hex(b)))
 
         return asm

tools/isledecomp/tests/test_instgen.py

@@ -0,0 +1,212 @@
+from isledecomp.compare.asm.instgen import InstructGen, SectionType
+
+
+def test_ret():
+    """Make sure we can handle a function with one instruction."""
+    ig = InstructGen(b"\xc3", 0)
+    assert len(ig.sections) == 1
+
+
+SCORE_NOTIFY = (
+    b"\x53\x56\x57\x8b\xd9\x33\xff\x8b\x74\x24\x10\x56\xe8\xbf\xe1\x01"
+    b"\x00\x80\xbb\xf6\x00\x00\x00\x00\x0f\x84\x9c\x00\x00\x00\x8b\x4e"
+    b"\x04\x49\x83\xf9\x17\x0f\x87\x8f\x00\x00\x00\x33\xc0\x8a\x81\xec"
+    b"\x14\x00\x10\xff\x24\x85\xd4\x14\x00\x10\x8b\xcb\xbf\x01\x00\x00"
+    b"\x00\xe8\x7a\x05\x00\x00\x8b\xc7\x5f\x5e\x5b\xc2\x04\x00\x56\x8b"
+    b"\xcb\xe8\xaa\x00\x00\x00\x8b\xf8\x8b\xc7\x5f\x5e\x5b\xc2\x04\x00"
+    b"\x80\x7e\x18\x20\x75\x07\x8b\xcb\xe8\xc3\xfe\xff\xff\xbf\x01\x00"
+    b"\x00\x00\x8b\xc7\x5f\x5e\x5b\xc2\x04\x00\x56\x8b\xcb\xe8\x3e\x02"
+    b"\x00\x00\x8b\xf8\x8b\xc7\x5f\x5e\x5b\xc2\x04\x00\x6a\x09\xa1\x4c"
+    b"\x45\x0f\x10\x6a\x07\x50\xe8\x35\x45\x01\x00\x83\xc4\x0c\x8b\x83"
+    b"\xf8\x00\x00\x00\x85\xc0\x74\x0d\x50\xe8\xa2\x42\x01\x00\x8b\xc8"
+    b"\xe8\x9b\x9b\x03\x00\xbf\x01\x00\x00\x00\x8b\xc7\x5f\x5e\x5b\xc2"
+    b"\x04\x00\x8b\xff\x4a\x14\x00\x10\x5e\x14\x00\x10\x70\x14\x00\x10"
+    b"\x8a\x14\x00\x10\x9c\x14\x00\x10\xca\x14\x00\x10\x00\x01\x05\x05"
+    b"\x05\x05\x02\x05\x05\x05\x05\x05\x05\x05\x05\x05\x03\x05\x05\x05"
+    b"\x05\x05\x05\x04\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc"
+)
+
+
+def test_score_notify():
+    """Score::Notify function from 0x10001410 in LEGO1.
+    Good representative function for jump table (at 0x100014d4)
+    and switch data (at 0x100014ec)."""
+    ig = InstructGen(SCORE_NOTIFY, 0x10001410)
+
+    # Did we get everything?
+    assert len(ig.sections) == 3
+    types_only = tuple(s.type for s in ig.sections)
+    assert types_only == (SectionType.CODE, SectionType.ADDR_TAB, SectionType.DATA_TAB)
+
+    # CODE section stopped at correct place?
+    instructions = ig.sections[0].contents
+    assert instructions[-1].address == 0x100014D2
+    # n.b. 0x100014d2 is the dummy instruction `mov edi, edi`
+    # Ghidra does more thorough analysis and ignores this.
+    # The last real instruction should be at 0x100014cf. Not a big deal
+    # to include this because it is not junk data.
+
+    # 6 switch addresses
+    assert len(ig.sections[1].contents) == 6
+
+    # TODO: The data table at the end includes all of the 0xCC padding bytes.
+
+
+SMACK_CASE = (
+    # LEGO1: 0x100cdc43 (modified so jump table points at +0x1016)
+    b"\x2e\xff\x24\x8d\x16\x10\x00\x00"
+    # LEGO1: 0x100cdb62 (instructions before and after jump table)
+    b"\x8b\xf8\xeb\x1a\x87\xdb\x87\xc9\x87\xdb\x87\xc9\x87\xdb\x50\xdc"
+    b"\x0c\x10\xd0\xe2\x0c\x10\xb0\xe8\x0c\x10\x50\xe9\x0c\x10\xa0\x10"
+    b"\x27\x10\x10\x3c\x11\x77\x17\x8a\xc8"
+)
+
+
+def test_smack_case():
+    """Case where we have code / jump table / code.
+    Need to properly separate code sections, eliminate junk instructions
+    and continue disassembling at the proper address following the data."""
+    ig = InstructGen(SMACK_CASE, 0x1000)
+    assert len(ig.sections) == 3
+    assert ig.sections[0].type == ig.sections[2].type == SectionType.CODE
+
+    # Make sure we captured the instruction immediately after
+    assert ig.sections[2].contents[0].mnemonic == "mov"
+
+
+# BETA10 0x1004c9cc
+BETA_FUNC = (
+    b"\x55\x8b\xec\x83\xec\x08\x53\x56\x57\x89\x4d\xfc\x8b\x45\xfc\x33"
+    b"\xc9\x8a\x88\x19\x02\x00\x00\x89\x4d\xf8\xe9\x1e\x00\x00\x00\xe9"
+    b"\x41\x00\x00\x00\xe9\x3c\x00\x00\x00\xe9\x37\x00\x00\x00\xe9\x32"
+    b"\x00\x00\x00\xe9\x2d\x00\x00\x00\xe9\x28\x00\x00\x00\x83\x7d\xf8"
+    b"\x04\x0f\x87\x1e\x00\x00\x00\x8b\x45\xf8\xff\x24\x85\x1d\xca\x04"
+    b"\x10\xeb\xc9\x04\x10\xf0\xc9\x04\x10\xf5\xc9\x04\x10\xfa\xc9\x04"
+    b"\x10\xff\xc9\x04\x10\xb0\x01\xe9\x00\x00\x00\x00\x5f\x5e\x5b\xc9"
+    b"\xc2\x04\x00"
+)
+
+
+def test_beta_case():
+    """Complete (and short) function with CODE / ADDR / CODE"""
+    ig = InstructGen(BETA_FUNC, 0x1004C9CC)
+    # The JMP into the jump table immediately precedes the jump table.
+    # We have to detect this and switch sections correctly or we will only
+    # get 1 section.
+    assert len(ig.sections) == 3
+    assert ig.sections[0].type == ig.sections[2].type == SectionType.CODE
+
+    # Make sure we captured the instruction immediately after
+    assert ig.sections[2].contents[0].mnemonic == "mov"
+
+
+# LEGO1 0x1000fb50
+# TODO: The test data here is longer than it needs to be.
+THUNK_TEST = (
+    b"\x2b\x49\xfc\xe9\x08\x00\x00\x00\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc"
+    b"\x56\x8b\xf1\xe8\xd8\xc5\x00\x00\x8b\xce\xe8\xb1\xdc\x01\x00\xf6"
+    b"\x44\x24\x08\x01\x74\x0c\x8d\x46\xe0\x50\xe8\xe1\x66\x07\x00\x83"
+    b"\xc4\x04\x8d\x46\xe0\x5e\xc2\x04\x00\xcc\xcc\xcc\xcc\xcc\xcc\xcc"
+    b"\x2b\x49\xfc\xe9\x08\x00\x00\x00\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc"
+    b"\xb8\x7c\x05\x0f\x10\xc3\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc"
+    b"\x2b\x49\xfc\xe9\x08\x00\x00\x00\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc"
+    b"\x8b\x54"
+    # The problem is here: the last two bytes are the start of the next
+    # function 0x1000fbc0. This is not enough data to read an instruction.
+)
+
+
+def test_thunk_case():
+    """Adjuster thunk incorrectly annotated.
+    We are reading way more bytes than we should for this function."""
+    ig = InstructGen(THUNK_TEST, 0x1000FB50)
+    # No switch cases here, so the only section is code.
+    # This caused an infinite loop during testing so the goal is just to finish.
+    assert len(ig.sections) == 1
+
+    # TODO: We might detect the 0xCC padding bytes and cut off the function.
+    # If we did that, we would correctly read only 2 instructions.
+    # assert len(ig.sections[0].contents) == 2
+
+
+# LEGO1 0x1006f080, Infocenter::HandleEndAction
+HANDLE_END_ACTION = (
+    b"\x53\x56\x57\x8b\xf1\x8b\x5c\x24\x10\x8b\x0d\x84\x45\x0f\x10\x8b"
+    b"\x7b\x0c\x8b\x47\x20\x39\x01\x75\x29\x81\x7f\x1c\xf3\x01\x00\x00"
+    b"\x75\x20\xe8\x59\x66\xfa\xff\x6a\x00\x8b\x40\x18\x6a\x00\x6a\x10"
+    b"\x50\xff\x15\x38\xb5\x10\x10\xb8\x01\x00\x00\x00\x5f\x5e\x5b\xc2"
+    b"\x04\x00\x39\x46\x0c\x0f\x85\xa2\x00\x00\x00\x8b\x47\x1c\x83\xf8"
+    b"\x28\x74\x18\x83\xf8\x29\x74\x13\x83\xf8\x2a\x74\x0e\x83\xf8\x2b"
+    b"\x74\x09\x83\xf8\x2c\x0f\x85\x82\x00\x00\x00\x66\x8b\x86\xd4\x01"
+    b"\x00\x00\x66\x85\xc0\x74\x09\x66\x48\x66\x89\x86\xd4\x01\x00\x00"
+    b"\x66\x83\xbe\xd4\x01\x00\x00\x00\x75\x63\x6a\x0b\xe8\xff\x67\xfa"
+    b"\xff\x66\x8b\x86\xfc\x00\x00\x00\x83\xc4\x04\x50\xe8\x3f\x66\xfa"
+    b"\xff\x8b\xc8\xe8\x58\xa6\xfc\xff\x0f\xbf\x86\xfc\x00\x00\x00\x48"
+    b"\x83\xf8\x04\x77\x2f\xff\x24\x85\x78\xf4\x06\x10\x68\x1d\x02\x00"
+    b"\x00\xeb\x1a\x68\x1e\x02\x00\x00\xeb\x13\x68\x1f\x02\x00\x00\xeb"
+    b"\x0c\x68\x20\x02\x00\x00\xeb\x05\x68\x21\x02\x00\x00\x8b\xce\xe8"
+    b"\x9c\x21\x00\x00\x6a\x01\x8b\xce\xe8\x53\x1c\x00\x00\x8d\x8e\x0c"
+    b"\x01\x00\x00\x53\x8b\x01\xff\x50\x04\x85\xc0\x0f\x85\xef\x02\x00"
+    b"\x00\x8b\x56\x0c\x8b\x4f\x20\x3b\xd1\x74\x0e\x8b\x1d\x74\x45\x0f"
+    b"\x10\x39\x0b\x0f\x85\xd7\x02\x00\x00\x81\x7f\x1c\x02\x02\x00\x00"
+    b"\x75\x1a\x6a\x00\x52\x6a\x10\xe8\xa4\x65\xfa\xff\x8b\xc8\xe8\x0d"
+    b"\xa2\xfb\xff\x66\xc7\x86\xd6\x01\x00\x00\x00\x00\x8b\x96\x00\x01"
+    b"\x00\x00\x8d\x42\x74\x8b\x18\x83\xfb\x0c\x0f\x87\x9b\x02\x00\x00"
+    b"\x33\xc9\x8a\x8b\xac\xf4\x06\x10\xff\x24\x8d\x8c\xf4\x06\x10\x8b"
+    b"\x86\x08\x01\x00\x00\x83\xf8\x05\x77\x07\xff\x24\x85\xbc\xf4\x06"
+    b"\x10\x8b\xce\xe8\xb8\x1a\x00\x00\x8b\x86\x00\x01\x00\x00\x68\xf4"
+    b"\x01\x00\x00\x8b\xce\xc7\x40\x74\x0b\x00\x00\x00\xe8\xef\x20\x00"
+    b"\x00\x8b\x86\x00\x01\x00\x00\xc7\x86\x08\x01\x00\x00\xff\xff\xff"
+    b"\xff\x83\x78\x78\x00\x0f\x85\x40\x02\x00\x00\xb8\x01\x00\x00\x00"
+    b"\x5f\x66\xc7\x86\xd2\x01\x00\x00\x01\x00\x5e\x5b\xc2\x04\x00\x6a"
+    b"\x00\x8b\xce\x6a\x01\xe8\xd6\x19\x00\x00\xb8\x01\x00\x00\x00\x5f"
+    b"\x5e\x5b\xc2\x04\x00\x6a\x01\x8b\xce\x6a\x02\xe8\xc0\x19\x00\x00"
+    b"\xb8\x01\x00\x00\x00\x5f\x5e\x5b\xc2\x04\x00\x8b\xce\xe8\x3e\x1a"
+    b"\x00\x00\x8b\x86\x00\x01\x00\x00\x68\x1c\x02\x00\x00\x8b\xce\xc7"
+    b"\x40\x74\x0b\x00\x00\x00\xe8\x75\x20\x00\x00\xb8\x01\x00\x00\x00"
+    b"\x5f\xc7\x86\x08\x01\x00\x00\xff\xff\xff\xff\x5e\x5b\xc2\x04\x00"
+    b"\x8b\xce\xe8\x09\x1a\x00\x00\x8b\x86\x00\x01\x00\x00\x68\x1b\x02"
+    b"\x00\x00\x8b\xce\xc7\x40\x74\x0b\x00\x00\x00\xe8\x40\x20\x00\x00"
+    b"\xb8\x01\x00\x00\x00\x5f\xc7\x86\x08\x01\x00\x00\xff\xff\xff\xff"
+    b"\x5e\x5b\xc2\x04\x00\xc7\x00\x0b\x00\x00\x00\x8b\x86\x08\x01\x00"
+    b"\x00\x83\xf8\x04\x74\x0c\x83\xf8\x05\x74\x0e\x68\xf4\x01\x00\x00"
+    b"\xeb\x0c\x68\x1c\x02\x00\x00\xeb\x05\x68\x1b\x02\x00\x00\x8b\xce"
+    b"\xe8\xfb\x1f\x00\x00\xb8\x01\x00\x00\x00\x5f\xc7\x86\x08\x01\x00"
+    b"\x00\xff\xff\xff\xff\x5e\x5b\xc2\x04\x00\x6a\x00\xa1\xa0\x76\x0f"
+    b"\x10\x50\xe8\x39\x65\xfa\xff\x83\xc4\x08\xa1\xa4\x76\x0f\x10\x6a"
+    b"\x00\x50\xe8\x29\x65\xfa\xff\x83\xc4\x08\xe8\xf1\x63\xfa\xff\x8b"
+    b"\xc8\xe8\x6a\x02\x01\x00\xb8\x01\x00\x00\x00\x5f\x5e\x5b\xc2\x04"
+    b"\x00\x8b\x47\x1c\x83\xf8\x46\x74\x09\x83\xf8\x47\x0f\x85\x09\x01"
+    b"\x00\x00\x6a\x00\x6a\x00\x6a\x32\x6a\x03\xe8\x91\x65\xfa\xff\x8b"
+    b"\xc8\xe8\xfa\xc7\xfd\xff\x8b\x86\x00\x01\x00\x00\x5f\x5e\x5b\xc7"
+    b"\x40\x74\x0e\x00\x00\x00\xb8\x01\x00\x00\x00\xc2\x04\x00\x8b\x47"
+    b"\x1c\x39\x86\xf8\x00\x00\x00\x0f\x85\xce\x00\x00\x00\xe8\xbe\x63"
+    b"\xfa\xff\x83\x78\x10\x02\x74\x19\x66\x8b\x86\xfc\x00\x00\x00\x66"
+    b"\x85\xc0\x74\x0d\x50\xe8\xa6\x63\xfa\xff\x8b\xc8\xe8\xbf\xa3\xfc"
+    b"\xff\x6a\x00\x6a\x00\x6a\x32\x6a\x03\xe8\x32\x65\xfa\xff\x8b\xc8"
+    b"\xe8\x9b\xc7\xfd\xff\x8b\x86\x00\x01\x00\x00\x5f\x5e\x5b\xc7\x40"
+    b"\x74\x0e\x00\x00\x00\xb8\x01\x00\x00\x00\xc2\x04\x00\x83\x7a\x78"
+    b"\x00\x75\x32\x8b\x86\xf8\x00\x00\x00\x83\xf8\x28\x74\x27\x83\xf8"
+    b"\x29\x74\x22\x83\xf8\x2a\x74\x1d\x83\xf8\x2b\x74\x18\x83\xf8\x2c"
+    b"\x74\x13\x66\xc7\x86\xd0\x01\x00\x00\x01\x00\x6a\x0b\xe8\xee\x64"
+    b"\xfa\xff\x83\xc4\x04\x8b\x86\x00\x01\x00\x00\x6a\x01\x68\xdc\x44"
+    b"\x0f\x10\xc7\x40\x74\x02\x00\x00\x00\xe8\x22\x64\xfa\xff\x83\xc4"
+    b"\x08\xb8\x01\x00\x00\x00\x5f\x5e\x5b\xc2\x04\x00\x8b\x47\x1c\x39"
+    b"\x86\xf8\x00\x00\x00\x75\x14\x6a\x00\x6a\x00\x6a\x32\x6a\x03\xe8"
+    b"\x9c\x64\xfa\xff\x8b\xc8\xe8\x05\xc7\xfd\xff\xb8\x01\x00\x00\x00"
+    b"\x5f\x5e\x5b\xc2\x04\x00\x8b\xff\x3c\xf1\x06\x10\x43\xf1\x06\x10"
+    b"\x4a\xf1\x06\x10\x51\xf1\x06\x10\x58\xf1\x06\x10\xdf\xf1\x06\x10"
+    b"\xd5\xf2\x06\x10\x1a\xf3\x06\x10\x51\xf3\x06\x10\x8e\xf3\x06\x10"
+    b"\xed\xf3\x06\x10\x4c\xf4\x06\x10\x6b\xf4\x06\x10\x00\x01\x02\x07"
+    b"\x03\x04\x07\x07\x07\x07\x07\x05\x06\x8d\x49\x00\x3f\xf2\x06\x10"
+    b"\x55\xf2\x06\x10\xf1\xf1\x06\x10\xf1\xf1\x06\x10\x6b\xf2\x06\x10"
+    b"\xa0\xf2\x06\x10\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc\xcc"
+)
+
+
+def test_action_case():
+    """3 switches: 3 jump tables, 1 data table"""
+    ig = InstructGen(HANDLE_END_ACTION, 0x1006F080)
+    # Two of the jump tables (0x1006f478 with 5, 0x1006f48c with 8)
+    # are contiguous.
+    assert len(ig.sections) == 5

tools/isledecomp/tests/test_sanitize.py

@@ -81,13 +81,23 @@ def test_jump_displacement():
     assert op_str == "-0x2"
 
 
-@pytest.mark.xfail(reason="Not implemented yet")
 def test_jmp_table():
-    """Should detect the characteristic jump table instruction
+    """To ignore cases where it would be inappropriate to replace pointer
-    (for a switch statement) and use placeholder."""
+    displacement (i.e. the vast majority of them) we require the address
+    to be relocated. This excludes any address less than the imagebase."""
     p = ParseAsm()
     inst = mock_inst("jmp", "dword ptr [eax*4 + 0x5555]")
     (_, op_str) = p.sanitize(inst)
+    # i.e. no change
+    assert op_str == "dword ptr [eax*4 + 0x5555]"
+
+    def relocate_lookup(addr: int) -> bool:
+        return addr == 0x5555
+
+    # Now add the relocation lookup
+    p = ParseAsm(relocate_lookup=relocate_lookup)
+    (_, op_str) = p.sanitize(inst)
+    # Should replace it now
     assert op_str == "dword ptr [eax*4 + <OFFSET1>]"