Posted: Sun Aug 04, 2013 6:30 pm Post subject: [Help]Size of opcodes
When i have to do code injections or asm edits where the size of opcodes matter, i always struggle to get the opcode length (bytes) and i have to assemble it somewhere, then look at Bytes column
random example:
chrome.exe+48B23 - 75 06 - jne chrome.exe+48B2B
chrome.exe+48B45 - E9 89FEFFFF - jmp chrome.exe+489D3
Is there a way to tell how many bytes does an opcode require without assembling it?
Joined: 09 May 2003 Posts: 25296 Location: The netherlands
Posted: Sun Aug 04, 2013 6:41 pm Post subject:
easiest method is just use the code injection template in the auto assembler.
it figures out the size of the instructions for you. You just have to make sure that nothing jumps inbetween the instruction(s) it's overwriting
But if you do it yourself you'll have to assemble it manually, or don't pick instructions that are affected by their position. (Jumps and calls are affected by their location) _________________
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