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James Taylor

Explain struct in assembly?

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James Taylor

I am having trouble understanding struct in assembly from disassembly. can you please explain the code below. Disassembly pseudo code.

Thanks

enter image description here

enter image description here

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evlncrn8
Posted (edited)

well you picked a terrible example...

as those arent really a good example for referencing structs.. they're just doing the strcpy inline

as dwords.. thats why its +4, +8 and so on, with a null terminator

4 th line in the asm for example

mov dword ptr [eax] , 'orP C'

mov dword ptr [eax+4], 'marg'

infact the only struct usage you'll probably see is in the book id portion

all the rest is just filling in strings into the structs

 

Edited by evlncrn8 (see edit history)

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kao

1) Get a basic book about assembly language. Read it and learn it. Then get a basic book about IDA disassembler. Read that too. That will answer all the questions you've asked so far on this forum and most of the questions you might ask in next few days.

2) If you're compiling your own example code to learn assembly language, disable all code optimizations in the compiler settings and enable PDB file generation. Make sure IDA loads the PDB file - it will make disassembly much more readable and understandable.

3) What you see in the disassembly screenshot, is inlined strcpy method. I don't want to repeat what's already be explained lots of times, so I'll just refer you to evlncrn8 's answer and https://reverseengineering.stackexchange.com/questions/18252/some-question-about-ida

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