Cheat Engine

Noobrzor · Last edited by Noobrzor on Fri Apr 29, 2016 3:54 pm; edited 1 time in total

Greetings

A)The script is for the game Dark Souls: Prepare to Die Edition. It's a health regeneration effect, restoring 2% of max health every second.
B)It works under normal circumstances, just as expected.
C)When a 'bleed effect bar' shows up indicating bleed effect being filled up (game mechanic) the game instantly crashes.
D)Under the 'bleed effect bar' the code doesn't access any other addresses but the one it does normally. Neither does the [eax+000002D8] value change.
E)I thought it was some flags being set. The original code is cmp function, which accesses a health value. Cmp sets flags for certain. So I modified the code to first do what I want and then, finally, do the originally intended cmp (therefore resetting the flags). Didn't help.
F) //-ing the div/idiv (removing it from the script) completely nullifies the problem. Since eax holds a high value the script gives a full-hp-every-second effect.

Now, I checked various assembly references. But for the life of me I can't figure out what is causing the script to go haywire. I have the various backups set and whatnot. Also, no need to advice on making the script neater or more efficient with push/pops, it's the way I learned and I'm sticking to it out of habit, since it doesn't really affect anything.

Script:

Cake-san · Posted: Fri Apr 29, 2016 3:02 pm Post subject:

Well,when I'm making health script, I always inject code that write to that address because it's more efficient. Like this:

Noobrzor · Posted: Fri Apr 29, 2016 3:47 pm Post subject:

I'm sorry, I don't quite understand?

First of all, I stated I'm not looking for more efficiency, just fixing a bug.
Second, what do you mean 'write to this address'? You mean a code that doesn't access a health address and then modified via injection to also write to the health address, but a code that specifically writes to this adress? If that's so, I would disagree - I like modifying code that only accesses an address, not inheretnly writes to it.
If you didn't mean that, then i don't know, because:
add [eax+000002D4],ecx
is adding ecx, which is the result of maxHP/50 (so 2% of maxhealth) to the address of health. I said it works as intended, only that dividing breaks it, and only in certain circumstances. And I wish to know the reason why is that happening.

Also, I apologize but I hardly understand your script.

Cake-san · Posted: Fri Apr 29, 2016 4:04 pm Post subject:

Instruction that write to address is intruction that make change to the value of that address like inc/dec it.

I had test you code and I see nothing wrong except if the the damage is greater than max health, then , you die.

Just test my script,then. You might see the difference.

Edited
Sorry, I didn't notice this:
regeneration Laughing

Zanzer · Posted: Fri Apr 29, 2016 4:07 pm Post subject:

Before IDIV, add:

Noobrzor · Posted: Fri Apr 29, 2016 5:24 pm Post subject:

Zanzer · Posted: Fri Apr 29, 2016 5:43 pm Post subject:

I suggested the fall through just so it executes the original code at the correct time.
No reason to do a CMP when you're about to do a bunch of other instructions.
Those instructions may throw off the conditional flags causing the game to make the wrong jump as it normally would.

When using divide, your dividend spans registers EDX:EAX.
So when you don't clear it, it's trying to divide by some random big number.
Whatever value you had in EDX was causing a divide exception.