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I am a newbie to RE and IDA Pro 7.2, and I am working my way through the book Practical Malware Analysis. I'm currently working on the lab 15-01 problem in the anti-disassembler chapter, but am having difficulty reproducing part of the solution in my environment.

I solved the lab by redefining some bogus opcodes into data, and now I have reasonable disassembly listings to look at. So far, so good. But at the end, the solution tells you to turn this fixed-up section into a function using the "P" hotkey. That doesn't work for me: I get this message in the output window:

.text:00401010: The function has undefined instruction/data at the specified address.
Your request has been put in the autoanalysis queue.

The address points to the first data definition I made.

Trying to flip over to graph mode doesn't work either. I get a popup that tells me that only instructions belonging to functions can be displayed in graph mode.

If I go to the Problems tab, I see lines like this:

.text:00401062  NONAME      db 0E8h

But I didn't glean anything in the IDA Pro help file for no name problems that helped me with my specific situation.

Ultimately, I used Edit -> Patch Program -> change byte to NOP out the data bytes and turn them into code. Then I had a function that I could graph.

My question is, is there a way to do this without patching bytes?

EDIT: Added error message text to the post.

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