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Old 06 December 2018, 16:15   #1
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Assembly Hex Help

Hello, I have downloaded a hex editor on Windows and opened an Amiga binary file. I have found a string in the binary (ex at location 6E0C7). I now want to find from where that string is referenced.

How do I go about looking for reference to this address location within the rest of the binary?

I tried doing a hex search for 6E0C7 but the search returned no result
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Old 06 December 2018, 16:17   #2
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Are you sure the Windows hex editor isn't displaying little endian byte-ordering?
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Old 06 December 2018, 16:31   #3
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This can get fairly tricky and I don't think big vs little endian alone is going to be the problem.

You see, the Amiga binary format (assuming the binary is one you load through Amiga OS and not say a custom a trackloader) does it's utmost best to avoid the use of 'addresses' and 'direct references' because of it's multitasking nature (which means the program can't know in advance at what memory location it runs).

In essence, Amiga OS relocates all code that does use 'direct' addresses when it loads a binary. To support this, Amiga binaries do not store actual addresses, but rather entries in a relocation table and references to these tables. Complicating matters further is that Amiga binaries support many smaller parts, called Hunks. Each of which contains a small part of the program or data. Each of these hunks can have their own style of relocation. It's difficult (though not impossible) to see how many hunks there are visually and decode them using just a HEX editor.

To top it all off, there is yet another problem: there are many ways to get to an address or offset using 68k code so even if the above didn't apply it still would not necessarily be as easy as looking for the address/offset.

There is a lot more to be said about this, but the short version would be that it may be difficult to do this using a HEX editor (due to the relocation done). Perhaps an option is to use WinUAE's debugger and some Amiga tools to find out what part of code references the data and where this code is located in the file?
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Old 06 December 2018, 16:33   #4
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A windows hex editor shows the same byte order of an Amiga file as an Amiga hex editor, but a windows executable would have a different order.

The problem is that most references to strings are made PC-relative like

LEA string_blabla(PC),A0


string_blabla DC.B "blabla",0

You can find these references with a good Amiga disassembler.
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Old 06 December 2018, 22:07   #5

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While a disassembler might be sufficient for that task, when you are willing to do some calculations (like PC-relative offsets and relocations) yourself, what you really need here is a reassembler.
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