Encoding question

[JenyaRostov]

Less of an issue and more of a question
How do i encode this:
mov eax, [someAddress]
i tried modifying ZydisEncoderRequest with this instruction, but changed displacement to a much larger value
from 503640 to 137616392292062
what do i need to change in my request? (request is generated from ZydisDecodedInstruction)

[athre0z]

Please provide your code and let us know how you determined the "incorrect" displacement to allow us to get a better idea of what is going wrong here. I suspect that this is likely due to rip relative addressing, but can't say for sure without further information.

[JenyaRostov]

kinda figured it out
my original instruction was with a small displacement and encoded as follows: 8B 05 4E650800 mov eax, [variable]
zydis correctly identified it as rip displacement
but to change displacement to a much larger value i had to this

which changes instruction to A1 E886D391F77F0000 (absolute address)

[JenyaRostov]

oops should've written it as reply

[mappzor]

If you want to remain RIP-rel you should set ZYDIS_REGISTER_RIP as mem.base. Best solution is to use ZydisEncoderDecodedInstructionToEncoderRequest and modify requests.operands[1].mem.displacement.

i tried modifying ZydisEncoderRequest with this instruction, but changed displacement to a much larger value
from 503640 to 137616392292062

RIP-rel displacements are limited to 32 bits and it's signed, so you cannot reference anything beyond -2GB and +2GB from RIP.