Cheat Engine

[SirCabby]

Hey all, I'm new to scripting and I've done a lot of reading and trials before posting. Hoping to continue expanding my understanding but starting to hit a bit of a roadblock on my ability.

I'm trying to do a somewhat tricky script. Here's what's going on:

1) There is a value that I've got a pointer to (multi-level pointer) that I've successfully mapped and can find on new games. I need to know when the value of this pointer is at 6.

2) When the above value is 6, I need to store the value of another pointer into a variable. This other pointer's value is a double type.

3) When the value of the first pointer is NOT 6, I want the script to copy the stored value back into the second pointer's location.

4) Regardless of pointer 1's value, I want the script to cycle on a ~10 second delay loop.

This script will be running continuously on a separate thread.

I've found most of this through various threads, but I've struggled to find posts that explain how to save the value of a register for a double, and then safely restore the register later. I know that different types of values should be handled in different registers. I was also wondering if it would be easier to manage all this through a LUA script instead of manipulating the memory directly. All guidance is greatly appreciated.

Here's a look at what I've come up with so far:

[MMM-304]

1st thing about thread is that every register in a new thread is free ie 0.

also when creating a new thread u dont need to allocate everything that u use inside the thread.

[SirCabby]

Thank you very much for going through this! I'll experiment and absorb what you suggested and reply in more depth when I've figured it out.

[SirCabby]

Ok I had time to dig into this. Thanks again for the feedback and help.

I have tweaked it a bit based on your advice, and put response comments as [SC] from me:

[SirCabby]

I guess at this point most of my question is really about working with doubles

I'll update the subject to reflect this.

[ParkourPenguin]

This would be far easier with Lua. Anyway...

• The third parameter to alloc isn't needed for 32-bit processes.
  
• You don't need that extra alloc for cleanup.
  
• The variables should be aligned. This is fine in the first post (everything has its own alloc), but labels should have an align pseudoinstruction before them.
  
• Why mix static and dynamic resolution of pointer paths? If only the first node doesn't change and can't be null, then I guess it's fine.
  
• {$try} / {$except} macros are a better alternative to what you're doing with null pointers.
  
• You didn't specify the value type of the first value in your first post, but I'm assuming it's a double.
  
• I really don't think you need to compare if the value is 0. (this goes against your third requirement)
  
• e** registers contain 4 bytes. Doubles take up 8 bytes.
  
• cmp is used for integer data, not floating point data.
  
• In x86 (32-bit), there is no way to move an 8 byte immediate in a single instruction.
  
• movsd can't move immediates, and comisd is used for comparing floating point numbers.
  
• You're redoing work by traversing part of the pointer path twice.
  
• Volatile registers can be used without being backed up with push/pop (this isn't a code injection)
  
• I don't know where you got xmm0 from. Throwing stuff at a wall won't help you much here.
  
• Passing 1000 to sleep is 1 second; 10000 would be 10 seconds.

Something like this:

[SirCabby]

I really appreciate the time you took to point out all the flaws in my example. It was very constructive and I learned a lot from seeing your example.

I was able to get this working based on your help!

I did have a few follow up questions though if you don't mind.

1) Is there a place for me to see what macros are available and how they work from your {$try} / {$except}? Are these Lua?

2) Since you mentioned it'd be a lot easier with Lua, I'd like to learn more... I found this link to get started but if you have anything better for someone at ground level knowledge can you please share? <snip-because-I-can't-post-urls-yet>cheatengine/index.php?title=Tutorials:Lua:Basics

3) When you say "movsd can't move immediates", from what I've learned immediates are constants in ASM? So I can't do something like "movsd xmm0,(double)6" because the 6 is an immediate? So by your storing it in a variable and then loading it into another register you're able to leverage movsd correct?

4) When you say "I don't know where you got xmm0 from. Throwing stuff at a wall won't help you much here.", I want to make sure I understand what you mean. I read up on register types and learned that xmm registers are used for floating point / double values... I thought I needed those. And I see you used them in your example as well. What was I doing wrong here?

Thanks again, really appreciate your help.

[ParkourPenguin]

1) Not really. I guess you can read the source code to see how it works, but that's not exactly easy.
I learned of this in particular by reading stuff on the forums (e.g. this post)

2) First, learn Lua. CE uses Lua 5.3 (Lua 5.4 is out now, but it's not worth switching to it). The best resource I know of is the book "Programming in Lua" (fourth edition), but there are plenty of free resources online.
Then, learn the stuff CE adds to Lua. I don't know of any easy and fast way of doing this. The file celua.txt is good but long. Browsing through the forums and the wiki can be faster but also might give some bad information.

3) Yes, that's exactly correct. If you look at an instruction set reference (e.g. this one), there are three opcodes associated with the movsd mnemonic:

[SirCabby]

Awesome, thanks for the follow up. I don't think my account is old enough to award rep yet but you've earned it either way.

Looking forward to growing more and contributing new tables.