CSL '0401' Program Binary Disassembly Notes

[karter16]

It appears that the memory space at 0x00ff8000 through 0x00ff87ff (which is managed by CS5 in the SIM module) is somehow a shared memory space between Master and Slave for global variables which need to be accessed by both functions that reside on the master and on the slave. I'm yet to confirm for sure or figure out exactly how it works, or whether there's some other mechanism at play.

[karter16]

Original post is now updated with link to the GitHub repo and some basic information on getting started. For anyone who is interested please have a look and let me know where you might need more info/guidance on getting up and running.

[karter16]

I know there isn't one for the CSL binary, I am still trying to figure out which binary it does belong to 😂

This is why I shouldn't reply to comments at work. Sorry. Yes interesting question - I haven't seen that information anywhere. I guess a way to do it would be to load each binary against it and see how much of it aligns, but that would be a huge amount of effort. Also I guess it's entirely possible the A2L is from during development and doesn't align exactly to any production binary.


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[bmwfnatic]

Ah I'm with you apologies - afaik there was never a correct A2L leaked for the CSL binary - others have pieced it together from the A2L that was leaked. It is incomplete and there are a range of parameters/curves and tables that seem specific to the CSL that are not identified by the A2L. This is part of the fun and as I'm going through I'm discovering where the XDF/A2L is incorrect.


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I know there isn’t one for the CSL binary, I am still trying to figure out which binary it does belong to 😂

[karter16]

Sounds good, but I meant more which binary belongs to the A2L.
I understand we intend to reverse the CSL bin.

Ah I'm with you apologies - afaik there was never a correct A2L leaked for the CSL binary - others have pieced it together from the A2L that was leaked. It is incomplete and there are a range of parameters/curves and tables that seem specific to the CSL that are not identified by the A2L. This is part of the fun and as I'm going through I'm discovering where the XDF/A2L is incorrect.


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[bmwfnatic]

Off the back of Heinz's suggestion I'm setting up a GitHub repo with the basics to enable multiple people to contribute to this. I'll share here as soon as it's good enough to share as a start. This will include the binary, etc (I'm using Terra's modified 0401 binary)


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Sounds good, but I meant more which binary belongs to the A2L.
I understand we intend to reverse the CSL bin.

[karter16]

Makes sense, which binary do we use for this?

Off the back of Heinz's suggestion I'm setting up a GitHub repo with the basics to enable multiple people to contribute to this. I'll share here as soon as it's good enough to share as a start. This will include the binary, etc (I'm using Terra's modified 0401 binary)


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[bmwfnatic]

Pretty much - the A2L/XDF gives you the memory locations and names of the parameters, curves and tables in the data space along with some somewhat questionable details around UOM etc. from there you can find the references to these in the program binary and start working backwards from there. The FunktionsRahmen helps a bit too with identifying some of the global var names, etc.


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Makes sense, which binary do we use for this?

[karter16]

How do you get started on this, using that leaked A2L and then using a matched binary and then just start cross referencing? Or is there something I am missing.

Pretty much - the A2L/XDF gives you the memory locations and names of the parameters, curves and tables in the data space along with some somewhat questionable details around UOM etc. from there you can find the references to these in the program binary and start working backwards from there. The FunktionsRahmen helps a bit too with identifying some of the global var names, etc.


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[bmwfnatic]

How do you get started on this, using that leaked A2L and then using a matched binary and then just start cross referencing? Or is there something I am missing.

[karter16]

Awesome, thanks for sharing! Let me know if you ever need/want help and I can try to jump in.

Would be nice to get this binary publicly disassembled so that we can write some custom features into the DME (e.g. current gear broadcast to retrofit the SMG screen in a manual car, MK60 brake pressure query over D bus and rebroadcast over CAN, etc.).

Can always leverage the wiki on the github repo if that works better than this thread.

The GitHub wiki is a good idea - I will look into that. I'd love as much help as possible, I'm just trying to figure out how I best set everything up that others can access and contribute to it while keeping some semblance of order.

[karter16]

Monolithic you say? Sounds copy-pastable to me!

haha - maybe - what I'm not sure about is what the code in the non-csl binary looks like that handles the TOG (oil level/temp sensor). Depending on how it was written and how the CSL version replaced it it may or may not be easy to add in the additional functionality. The way the CSL version is written I'm guessing it was a fairly brute-force replacement of the original code, but maybe not. (I'd love to look into it, but this is all very time consuming and trying to take the time to get the basics in place first to aid in better understanding of the code).

[heinzboehmer]

Monolithic you say? Sounds copy-pastable to me!

[karter16]

Would love to figure out the oil level read out to be able to get it working on non CSL HP DME tunes

I was actually looking through this function yesterday. It stands out as a feature that was added in afterwards for a couple of reasons.

1: It's a monolithic function - the decompiled C code is 700 lines, this is much larger than most other functions which are much more modular in design.
2: It has repeated calls to lookup the same table values in different if/else statements. The rest of the binary is carefully written to prepare the inputs and do a single table lookup, but this one has clearly been written differently in a different style.

It will be a non-trivial exercise to reverse engineer it completely, however for your purpose the key would be to identify the various inputs and outputs, their relative locations in your target binary and go from there.

[nextelbuddy]

Awesome, thanks for sharing! Let me know if you ever need/want help and I can try to jump in.

Would be nice to get this binary publicly disassembled so that we can write some custom features into the DME (e.g. current gear broadcast to retrofit the SMG screen in a manual car, MK60 brake pressure query over D bus and rebroadcast over CAN, etc.).

Can always leverage the wiki on the github repo if that works better than this thread.

Would love to figure out the oil level read out to be able to get it working on non CSL HP DME tunes