Lua Do String

[kingdeking]

Hello,

I am trying to find this function in WoW but its hard, can you help me a bit? I used Lua Func in game, set breakpoint and looked up where it was called from. Now i have one function that is called all the time and calls different Lua functions, it takes 3 parameters, one is the lua state ptr.

[Vandra]

How i'm doing it:

public void LuaDoString(string command)
        {
            int nSize = command.Length + 0x100;
            uint codeCave = process.AllocateMemory(nSize);
            uint moduleBase = (uint)process.MainModule.BaseAddress;

            process.WriteASCIIString(codeCave, command);

            process.Asm.Clear();

            String[] asm = new String[] 
            {
                "mov eax, " + codeCave,
                "push 0",
                "push eax",
              
                "push eax",
                "mov eax, " + (moduleBase + Offsets.Endscene.Lua_DoStringAddress),
                
                "call eax",
                "add esp, 0xC",
                "retn",    
            };

            vLib.InjectAndExecute(asm);
            process.FreeMemory(codeCave);
        }

[kingdeking]

Ye ye, just wondering how to get the return value :/

[Empted]

Hello,

            wow.WriteASCIIString(varName, variable);
            wow.Asm.AddLine("mov ecx, {0}", player.BaseAddress);
            wow.Asm.AddLine("push {0}", -1);
            wow.Asm.AddLine("push {0}", varName);
            wow.Asm.AddLine("call {0}", (uint)wow.MainModule.BaseAddress + (uint)Offsets.eWowFunctions.FrameScript__GetLocalizedText);
            wow.Asm.AddLine("mov dword [{0}], eax", returnValue);

Simply try putting return value into variable with some name, like myVariable=SomeFunction(). Then you create string with that variable name you need to get value from (ASCII encoded) and call FrameScript__GetLocalizedText with 3 params you can see above. It returns you a pointer to a string with UTF encoding that you can simply read and get your return value.
Offset for FrameScript__GetLocalizedText is 0x43C230+(wow main module adress).
Btw reading UTF string can be done something like this:

                byte[] bytes = wow.ReadBytes(wow.ReadUInt(returnValue), 0x50);
                string decodedBytes = Encoding.UTF8.GetString(bytes);
                sResult = decodedBytes.Split('\0')[0];

[migtron]

Assuming you mean FrameScript::ExecuteBuffer by "Lua_DoString", that function uses cdecl calling conventions and as such returns the result in EAX. But are you sure you actually need its return value? I don't know for sure what it returns in 4.3.4 and after a quick glance at the code I would wildly guess... the Lua stack size maybe? Or some error code? Doesn't seem like anything useful at least.

[kingdeking]

Okay guys, thanks for all the help but I managed to reverse it myself. My assumption in the first post was correct luckily. The return value can be found in different places of the lua_state object.

Most integer values go to

mov eax, [Lua_State_PTR+C];
mov ret, [eax]

[Vandra]

Ye ye, just wondering how to get the return value :/

Then you need GetLocalizedText, and not DoString

[kingdeking]

btw, different question, how do you determine if a battleground is over?

[Vandra]

UPDATE_BATTLEFIELD_STATUS event

or BATTLEFIELDS_SHOW maybe

[kingdeking]

Okay. So these are fields somewhere in WoW I can read right? So I should get a pointer to these when reversig RegisterEvent() Api right?

[Empted]

You can probably hook those events in Lua and modify some of your variables once event hits. And check that variable using GetLocalizedText.

[kingdeking]

Thanks. But what is GetLocalizedText doing? :confused: What is it good for?

[Empted]

Look my post above. It get's value from variable by name. And because of lua being dynamically typed language it will always get string value.
Btw calling GetLocalizedText to check variable can be bad for perfomance, so i guess it's better first to find adress of variable and just memory read.