dreadful

An IDA Pro plugin to help in disassembly of Metroid Dread.

• src/dreadful-ast-matcher: Encapsulates parts of the code of the plugin that call into Clang.
• src/dreadful-plugin-ida-base: Encapsules parts of the code of the plugin that call into IDA's SDK.
• src/dreadful-plugin-dump: A simple plugin, unrelated to Metroid Dread, that dumps pseudocode consumable by Clang in IDA's output window.
• src/dreadful-plugin: The actual implementation of the plugin.

Supported versions

	MD5	State
V1.0	F5D9AA2AF3ABEF3070791057060EE93C	WIP

Implementation details

⚠️ We recommend running this plugin on a blank IDB.

1. Search for calls to CRC64 (the offset of which is the only hardcoded value, and specified per-binary version)
2. For all occurences, search for (what we hereafter refer to) reflobjects constructors:
   They should look something like this:
   Note that this is the output of code generated by the plugin, and may differ from the default pseudocode generated by Hex-Rays.
   From there, we extract all constant property values; that is, integers and function pointers.
3. We then look for callers to the function analyzed in the previous step; there should only be one, and will be denoted as the reflobject accessor. They should look something like this:
   
4. From there, we can deduce the actual name of the type for which the reflobject is constructed, its base type, publicly exposed functions, and member variables.

Gotchas

Constructors implementations can be inlined in the function calling them

Below is a function where the constructor got inlined into the GetReflInfo method, causing all memory writes to be directly in .bss. This usually only happens for reflection information pertaining to built-in types.

_QWORD *sub_71000A3A30()
{
  ...

  v0 = __ldar(&qword_7101D02BD8);
  if ( (v0 & 1) == 0 && _cxa_guard_acquire_0(&qword_7101D02BD8) )
  {
    sub_71000003D4(&v7, "unsigned char", 1);
    v2 = CRC64("unsigned char", 0xDuLL);
    qword_7101D02AF8 = (unsigned __int64)&off_71019C5550;
    *(&qword_7101D02AF8 + 1) = (Any)v7;
    if ( qword_7101CEE108 + 16 != v7 )
      ++*(_DWORD *)(v7 + 8);
    *(&qword_7101D02AF8 + 2) = (Any)v2;
    *(&qword_7101D02AF8 + 3) = 1LL;
    qword_7101D02B48 = 0LL;
    qword_7101D02B50 = (unsigned __int64)sub_71000A3C0C;
    dword_7101D02B18 = 0xFFFFFFFF00000000LL;
    qword_7101D02B20 = 0LL;
    qword_7101D02B28 = 0LL;
    qword_7101D02B30 = 0LL;
    qword_7101D02B58 = (unsigned __int64)sub_71000A3C20;
    qword_7101D02B60 = (unsigned __int64)sub_71000A3C28;
    qword_7101D02B38 = 0LL;
    qword_7101D02B40 = 0LL;
    LOBYTE(byte_7101D02B9C) = 1;
    qword_7101D02B68 = (unsigned __int64)nullsub_341;
    qword_7101D02B70 = 0LL;
    qword_7101D02B78 = 0LL;
    qword_7101D02B80 = 0LL;
    LODWORD(dword_7101D02B98) = 10;
    LODWORD(dword_7101D02BA0) = 62;
    qword_7101D02B88 = 0LL;
    qword_7101D02B90 = 0LL;
    v3 = sub_71000836A0();
    qword_7101D02BC8 = 0x3E0000000ALL;
    qword_7101D02BA8 = (Any)v3;
    qword_7101D02BB0 = 0LL;
    qword_7101D02BB8 = 0LL;
    qword_7101D02BC0 = 0LL;
    qword_7101D02BD0 = sub_71000836A0();
    qword_7101D02B20 = (unsigned __int64)sub_71000A3C2C;
    qword_7101D02B28 = (unsigned __int64)sub_71000A3C34;
    qword_7101D02B30 = (unsigned __int64)sub_71000A3C40;
    qword_7101D02B38 = (unsigned __int64)nullsub_207;
    v4 = (Any)qword_7101CEE108;
    qword_7101D02B40 = (unsigned __int64)sub_71000A3C50;
    qword_7101D02B48 = (unsigned __int64)sub_71000A3C64;
    LODWORD(dword_7101D02B18) = (Any)dword_7101D02B18 & 0xFFFFFFFC;
    if ( qword_7101CEE108 )
    {
      v5 = (Any)v7;
      if ( v7 )
      {
        if ( v7 != qword_7101CEE108 + 16 )
        {
          v6 = *(_DWORD *)(v7 + 8) - 1;
          *(_DWORD *)(v7 + 8) = (Any)v6;
          if ( !v6 )
          {
            sub_7100080124(v4, v5);
            v4 = (Any)qword_7101CEE108;
          }
        }
      }
      v7 = (Any)v4 + 16;
    }
    sub_7100000250(sub_710009C914, &qword_7101D02AF8, &off_71019C3000);
    _cxa_guard_release_0(&qword_7101D02BD8);
  }
  return &qword_7101D02AF8;
}

This is supported by first looking for the vtable assignment and using that as a base address for all following writes. The byproduct of this is that every parameter is inlined in the call site, meaning we don't need to perform step 3 of our algorithm, and can just move on.

`base::global::CStrId` inlining

Much to our dismay (as customary when dealing with compilers), calls to base::global::CStrId (which we look for to identify the name of the type for which reflection data is constructed) can get inlined when the construction of said reflection data is called from large functions that construct more than once.

In those situations, we instead look for what is effectively a call into the game's string pool, tasked with pooling the string, which got inlined in the call parameters. However, because Hex-Rays will reuse pseudoregisters across occurences of this code, we only consider calls that are less than 15 lines of code away from the call site of interest (which, realistically, is far more than enough).