General IDA 6816 question

General IDA 6816 question

Postby EFI-Unlimited » Mon Jan 02, 2012 4:08 pm

I am disassembling code from an older Chrysler vehicle. It uses the 68HC16 processor like the older Subaru's did. I am having an issue that I am hoping someone here has experience with.

I have several instructions that use a single immediate EXT operand that is getting flagged as 'bad' or 'suspicious' by IDA. It marks the operand in RED, and wont let me define it as an offset. Consequently, my listing is missing a lot of data, because it wont let me flag it.

I have tried changing the high/low suspiciousness limits, with no difference. Is this a bug in the processor module?

Brian
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Re: General IDA 6816 question

Postby Rhinoman » Fri Jan 06, 2012 4:00 am

Did you resolve this? I've had this problem as well in the past, I think it was with the index register offsets.
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Re: General IDA 6816 question

Postby EFI-Unlimited » Fri Jan 06, 2012 1:58 pm

Nope, no resolution yet.

I also have found several cases of data addresses that are referenced at several locations in the code, but when your actually at that data location, and you select 'show xrefs to...' it says there are no xrefs to the data, when there are in fact several.

I haven't figured out anything in common between the stuff that works and the stuff that doesn't, so I'm not sure how to work around it. Mostly, I want to find out if its something I'm doing, or something that I have to live with. By the way its sounding, I guess I'll just have to live with it.

Brian
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Re: General IDA 6816 question

Postby Rhinoman » Fri Jan 06, 2012 2:27 pm

Its rather odd because I only had this problem on one ECU, several others worked OK.
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Re: General IDA 6816 question

Postby EFI-Unlimited » Fri Jan 06, 2012 4:14 pm

I haven't looked too closely, but I know that some of the addresses that have the issue are part of an instruction that uses EXT addressing, rather than IMM, Z or otherwise. It seems as though this is a bug in the IDA processor module. Maybe someone can bring this up to Ilfak.

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Re: General IDA 6816 question

Postby Rhinoman » Wed Jan 18, 2012 5:06 am

I've just had a similar issue with an H8/532 binary, the address were highlighted red. When I tried to name the locations IDAPro asked me to define a section (segment?), once I did that the red highlight disappeared. I have a new problem now though, my disassembly is one byte short, I can't get it to list 0xFFFF :?
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Re: General IDA 6816 question

Postby EFI-Unlimited » Fri Jan 20, 2012 4:28 pm

I might see if some segment shenanigans are to blame. I haven't played with it lately. For what it's worth, I'm using the "Z" 6816 module. I might see if I can try colby's processor module.

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