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Thread: ROM disassembly


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Permlink Replies: 22 - Pages: 2 [ Previous | 1 2 ] - Last Post: Oct 29, 2013 12:24 PM Last Post By: bbraun Threads: [ Previous | Next ]
jduerstock

Posts: 10
Registered: 6/30/13
Re: ROM disassembly
Posted: Jun 30, 2013 5:39 PM   in response to: bbraun in response to: bbraun
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Apparently we have some similar interests:

https://github.com/jduerstock/5bf10fd1

My version of it builds using GNU binutils with m68k support.
bbraun


Posts: 493
Registered: 7/25/12
Re: ROM disassembly
Posted: Jun 30, 2013 7:29 PM   in response to: jduerstock in response to: jduerstock
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Nice! So that looks like the AV ROM?
I've found the AV ROM doesn't actually boot earlier machines that work with dougg3's ROM SIMM. The AV machines have pads for SIMM sockets, but dougg3 found they are incompatible with his ROM SIMM unfortunately.
Are you just using your ROM with emulators?
jduerstock

Posts: 10
Registered: 6/30/13
Re: ROM disassembly
Posted: Jun 30, 2013 11:29 PM   in response to: bbraun in response to: bbraun
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Yes, that's the AV ROM.

I mostly wanted to know how things like the AT&T 3210 DSP worked, etc., but I've gotten amused and distracted along the way several times.

Currently my new interest is the "Classic" emulation in OS X 10.4, since you can still pop into the debugger there. If there's anything particular you want me to look at or poke at, let me know.
superpete

Posts: 18
Registered: 4/4/13
Re: ROM disassembly
Posted: Jul 2, 2013 12:32 AM   in response to: jduerstock in response to: jduerstock
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I know this is off topic, but I'd be interested to see what you discover in your Classic hacking. I'm rather interested to see if there are any hooks in the Classic distribution which modern emulators might be able to use to allow more seamless integration. A bit like greybox for OS 9 apps.
bbraun


Posts: 493
Registered: 7/25/12
Re: ROM disassembly
Posted: Jul 3, 2013 8:40 PM   in response to: jduerstock in response to: jduerstock
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Out of curiosity, did you use objdump to disassemble the ROM, then add symbols by hand?
It'd be pretty handy to be able to reassemble the ROM. I notice with yours it's not entirely disassembled, so you can't change any offsets when reassembling. That'd still be useful since I typically end up overwriting unused or disabled code, like the RAM test routines. Being able to convert the fdisasm files I've got to work as input to whatever you used to disassemble would be nice.
jduerstock

Posts: 10
Registered: 6/30/13
Re: ROM disassembly
Posted: Jul 3, 2013 11:42 PM   in response to: bbraun in response to: bbraun
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Initially I used objdump, then I did some scripting to get the offsets and values in the comments. The progress was sort of haphazard, because there are a few quirks from what got disassembled to reassembly (especially in the vector stuff). I've also used IDA Pro to guide my work around sometimes.
bigmessowires


Posts: 217
Registered: 10/29/13
Re: ROM disassembly
Posted: Oct 29, 2013 1:18 AM   in response to: bbraun in response to: bbraun
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What's your goal with this disassembly project - to produce something like the commented ROM disassemblies for older Macs at http://minivmac.sourceforge.net/extras/fdisasm.html, but for the IIsi? Or something more detailed?

The stuff bundled with FDisasm is a great start, but still leaves a lot of ground uncovered. A while back, I spent a ton of time poring through the Mac Plus ROM and adding more annotations, and eventually submitted it all back to Paul Pratt who maintains FDisasm.
bbraun


Posts: 493
Registered: 7/25/12
Re: ROM disassembly
Posted: Oct 29, 2013 12:24 PM   in response to: bigmessowires in response to: bigmessowires
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Originally, my disassembly was mainly for the ROM Disk driver I did for dougg3's ROM SIMM. Figuring out patching the boot process, adding the custom driver, patching out the memory test and checksum validation, finding "unused" sections of code I could commandeer for adding my own code, etc.

But, the fdisasm disassembly is kind of a monotonous, mind numbing, repetitive task in a good, relaxing sort of way, so I kept going. Eventually I had to stop so I could get other things done. :)

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