CODEWITHSUNDEEP
assemblyx86patchdisassemblyida
user3712482
user3712482

Reputation: 113

IDA "Invalid Operand" error when patching

I am attempting to patch a binary in IDA using the "Assemble" option, and every time I enter an instruction with some arithmetic to calculate the offset, I receive an Invalid Operand error. For example:

mov [bp-4], bx

returns Invalid Operand, while

mov ax, bx

works.

I've attempted playing around with the format of the instruction (eg include word ptr, use 4h, etc) but nothing seems to work. Is there any way about this error, or is entering byte code for patching the only option?

Upvotes: 6

Views: 7830

Answers (2)

tomysshadow
tomysshadow

Reputation: 932

A bit late, but although the Assemble dialog says "Invalid operand" if you know the bytecode you can use the Change byte... menu option instead. You could use OllyDbg to assemble to bytecode (select anywhere and hit space), then copy that into IDA's Change byte dialog as a workaround.

Upvotes: 2

Orwellophile
Orwellophile

Reputation: 13933

according to Hex Rays:

The assembler command is supported for only a few processors, only a few instructions. We do not plan to extend this feature, sorry

Lame, I know.

Upvotes: 7

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