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| − | <!-- Tutorial:CodeInjection_Integers --> | + | <span style="font-size:25px;color:red">Sorry! Content not available.</span> |
| − | [[Category:Tutorial]]
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| − | [[Category:Auto Assembler]]
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| − | {{DISPLAYTITLE:Code Injection - Working with Integers}}
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| − | This tutorial builds on the topic of Code Injection:
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| − | {{TutorialsCodeInjection}}
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| − | | |
| − | <br>
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| − | Let's say you have an integer and some code that increases the value.
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| − | <pre>
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| − | add [eax+10],ecx
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| − | </pre>
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| − | <blockquote>
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| − | What if what writes to the value is only a [[Assembler:Commands:MOV|MOV]]. Try to find a spot above the write instruction that has an [[Assembler:Commands:ADD|ADD]] (or a [[Assembler:Commands:SUB|SUB]] depending on what you want to do).
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| − | <pre>
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| − | add ecx,ebx
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| − | //...
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| − | mov [eax+10],ecx
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| − | </pre>
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| − | </blockquote>
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| − | | |
| − | <br>
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| − | == Hardcoded value == | |
| − | We could just hardcode a value for this.
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| − | <pre>
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| − | add dword ptr [eax+10],(int)100 // #100 //// "#" is a short hand for integer
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| − | </pre>
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| − | | |
| − | <br>
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| − | == Editable value ==
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| − | We could use a [[Auto Assembler:label|label]], giving it some memory. And optionally [[Auto_Assembler:registerSymbol|register]] it so the label can be used on the table as an address.
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| − | <pre>
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| − | //...
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| − | alloc(someMem, 0x400)
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| − | //...
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| − | label(someSymbol)
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| − | registerSymbol(someSymbol)
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| − | //...
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| − | someMem:
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| − | //...
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| − | mov ecx,[someSymbol]
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| − | add [eax+10],ecx
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| − | //...
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| − | jmp return
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| − | //...
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| − | someSymbol:
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| − | dd (int)100
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| − | //...
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| − | </pre>
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| − | | |
| − | <br>
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| − | == Adding a Multiplier ==
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| − | We could add an editable value like above but use [[Assembler:Commands:IMUL|IMUL]] to add a multiplier to the script.
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| − | <pre>
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| − | //...
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| − | alloc(someMem, 0x400)
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| − | //...
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| − | label(someSymbol)
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| − | registerSymbol(someSymbol)
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| − | //...
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| − | someMem:
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| − | //...
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| − | imul ecx,[someSymbol]
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| − | add [eax+10],ecx
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| − | //...
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| − | jmp return
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| − | //...
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| − | someSymbol:
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| − | dd (int)10
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| − | //...
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| − | </pre>
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| − | | |
| − | <br>
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| − | == Fractional Multiplier ==
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| − | But what if we wanted to be able to multiply by a fractional number (i.e.: "0.5"). Well this can take a bit more, but we can use [[Assembler:Commands:CVTSI2SS|CVTSI2SS]] and [[Assembler:Commands:CVTSS2SI|CVTSS2SI]] to convert the value form an integer to a float and back a gain. Then we can just use [[Assembler:Commands:MULSS|MULSS]] to do the multiplying, but we will need an [[Assembler#Structure|XMM]] [[Assembler#Registers|registry]] to work with. So we will need some extra memory and use [[Assembler:Commands:MOVUPS|MOVUPS]] to save and restore the XMM registry.
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| − | <pre>
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| − | //...
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| − | alloc(someMem, 0x400)
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| − | //...
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| − | label(someSymbol)
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| − | registerSymbol(someSymbol)
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| − | label(extraStuff)
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| − | //...
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| − | someMem:
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| − | //...
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| − | movups [extraStuff],xmm0 //// save
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| − | cvtsi2ss xmm0,ecx
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| − | mulss xmm0,[someSymbol]
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| − | cvtss2si ecx,xmm0
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| − | movups xmm0,[extraStuff] //// restore
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| − | //...
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| − | jmp return
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| − | //...
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| − | someSymbol:
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| − | dd (int)10
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| − | extraStuff:
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| − | dd 0 //// Data double-word (4 bytes)
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| − | dd 0
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| − | dq 0 //// Data quad-word (8 bytes)
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| − | //...
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| − | </pre> | |
| − | | |
| − | <br>
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| − | == Calculate a value for a Multiplier ==
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| − | Let's say we just can't find an [[Assembler:Commands:ADD|ADD]] or a [[Assembler:Commands:SUB|SUB]], and all we have is a [[Assembler:Commands:MOV|MOV]].
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| − | <pre>
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| − | mov [eax+10],ecx
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| − | </pre>
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| − | | |
| − | We can just do some math in the script, to calculate a value for a multiplier.
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| − | <pre>
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| − | //...
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| − | alloc(someMem, 0x400)
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| − | //...
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| − | label(someSymbol)
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| − | registerSymbol(someSymbol)
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| − | //...
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| − | someMem:
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| − | //...
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| − | sub ecx,[eax+10]
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| − | imul ecx,[someSymbol]
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| − | add ecx,[eax+10]
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| − | mov [eax+10],ecx
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| − | //...
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| − | jmp return
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| − | //...
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| − | someSymbol:
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| − | dd (int)10
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| − | //...
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| − | </pre>
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| − | | |
| − | <br>
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| − | == See Also ==
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| − | {{TutorialsAA}}
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