Does anyone ever succeeded in installing MAtConvNet under Octave ?
If so could you please let me know the steps to proceed ?
thanks and regards
Arno
I was just looking into this issue myself. I have reached a point in researching this where I feel the issues are too complicated for my own project and are not worth my time trying to finish running down. However, if someone else is determined to track this down, hopefully this information will help.
The basic problem comes down Octave only compiling to support 32-bit architectures even if you use the 64-bit installer. If you want Octave to support 64-bit, you need to compile from source using the appropriate compiling options. The other details are as follows.
MatConvNet appears to require a 64-bit system to compile.
http://www.vlfeat.org/matconvnet/mfiles/vl_compilenn/
MatConvNet detects system architecture in in the mex_cuda_config function in vl_compilenn.m:
https://github.com/vlfeat/matconvnet/blob/master/matlab/vl_compilenn.m
Octave's computer function is not a perfect analog to Matlab's function, so the mex_cuda_config function in vl_compilenn.m would need to be modified or Octave's computer function would need to be updated. More specifically, the computer function's handling of the 'arch' argument needs to be changed.
There may be other issues, but this is where I would start if I had the time to invest in trying to track this down.
Related
I want to disassemble Wii game executable binaries in C, which use the broadway microprocessor and unfortunately the only disassembler I am aware that I can use is libopcodes.
Documentation about this library is scarce and I'm using this tutorial https://blog.yossarian.net/2019/05/18/Basic-disassembly-with-libopcodes to get a basic disassembler, from which (after reading) I copy pasted the last complete code snippet. I initially used the default binutils version of Ubuntu 20, which worked for the x86 architecture but immediately segfaulted with no output for my architecture of interest (bfd_arch_powerpc and bfd_mach_ppc_750). I now built from source the latest binutils version (2.39.50), which now demands an fprintf_styled argument (I provided a very simple one which vprintfs to stdout). Now I am getting an a floating point exception on buffer_read_memory (?) when disassembling the tutorial's architecture and a segfault when diassembling mine.
I am not familiar at all with libopcodes and am pretty much blindly following the only tutorial I could find for it on the internet. If anyone could help be up to create a basic powerpc disassembler with libopcodes that disassembles a void* buffer (or at least point me to any resource) it would be greatly appreciated.
A ppc example usage of libbfd can be seen in the disasm() function of qtrace-tools/qtdis. This is used to disassemble a buffer of powerpc64 instructions.
I solved my issue. I had to install binutils-multiarch-dev to support bfd_arch_powerpc and bfd_mach_ppc_750. In my case, I also had to remove my custom installation of binutils because the custom build with no flags apparently does not support PowerPC and dis-asm.h from /usr/local/include was taking priority over the one in /usr/include.
I am currently trying to solve a reversing challenge, where c code is compiled for a 32bit linux system.
To solve this challenge I am trying to make use of ghidra but am faced with a few issues. A bit of a summary what I have done up to this point:
I have two OS available to me, one 64bit Linux System on my Laptop and this 64bit Windows 10. Apparantly the programm was compiled with gcc without a -g option making ghidra fail to debug the programm. Manually debugging it with gdb in Terminal is possible but terrible to use (at least for me).
So all I can do is look at the assembler code in the CodeBrowser of Ghidra and its respective decomipled c code. With that I got to understand that some of the instructions are decrypted during the runtime of the programm and in order to further analyse the code, I want to be able to execute parts of the instructions to slowly but surely decrypt and understand the hidden parts of the programm.
That being said, the only issue here is that I do not know how I can do that. I have noticed that ghidra has the ability to run java code, but all the examples I looked at that were provided by ghidra allow me to only patch hardcoded instructions into the programm but not to actually execute/evaluate them.
My specific issue at hand is following part of the programm (green marked part):
Ghidra has all the knowledge it needs to execute this part and I just do not know how to do that. I could of cause do it by hand, but that is just boring and not really why I am doing these challenges and that is the same reason as why I am not looking for finished scripts that unpack this programm for me but for a way to execute my analysis.
Finally to summarize my question: I am asking for a way to execute the green marked decrypting part of the targeted programm in ghidra without starting the debugger (since the ghidra debugger keeps failing on me).
I think you are mixing up a few things here. You say:
the programm was compiled with gcc without a -g option making ghidra fail to debug the programm
The debug information added with -g makes it easier to analyze and debug a program because you have information that would have otherwise have to be recovered by reverse engineering. This should not have an influence on whether you can run the program under a debugger in the first place, and as you noted running it with gdb in the terminal works. The Ghidra debugger basically just runs gdb in the background and attaches to it to exchange information, so it should work.
You have a few options now:
1. Get the Ghidra Debugger to run with this binary
Whatever issue you are encountering with the Ghidra debugger is probably a valid question for https://reverseengineering.stackexchange.com/
From then on you can pursue your initial plan to solve this via debugging.
2. Write a GhidraScript to reimplement the decryption
Understand the basic idea of what you recognized correctly as some kind of decryption loop. Then you can use one of Ghidra's scripting options[0] to write a simple script that reimplements this decryption, but writes the decrypted values to the Ghidra memory directly.
Any scripting language will obviously include basic arithmetic operations like + -, and xor and loops, and the Ghidra API provides the functions byte getByte(Address address) and setByte(Address address, byte value). If you encounter any issues or API questions while writing this script that will also be a valid follow up question for the RE Stack Exchange.
This approach has the advantage that you can then statically analyse the resulting data inside Ghidra again, e.g. disassemble the resulting code.
[0] Ghidra natively supports Python 2.7 and Java based Scripts and a rudimentary Python REPL, but there are other options like Jupyter and Script based Kotlin or Ruby, Kotlin and Clojure Scripts
At first I was excited about working on open development projects for Octave related to implementing programs heavy in mathematics and physics, such as delaunayTriangulation class, but after talking to a few octave maintainers I have come to the sad conclusion that Octave will be complete after classdef is complete, at which point physics or mathematician like programmers will no longer be needed to build new functionality to Octave. Is this true?
I have followed your thread on the Octave maintainers mailing list and I think you have misunderstood this quite badly.
Once classdef gets implemented, the problems won't be solved, quite the contrary. It will allow for many problems to be solved, which can't be done just yet in a Matlab compatible way. There are 2 things here:
you may have felt that there's no problems left to solve after seeing many suggestions of libraries that already solve the problem. That doesn't mean they will be used. Even if licensing allows it, there comes a point where having to "reshape" the data in Octave into whatever form the other library uses it, is just too much and a native interface is preferred. This is specially true in Octave because it's mostly written in the Octave language which allows for users to participate in its development.
Even if an external library is used in the end, remember that "the devil is in the details". Implementing an interface between Octave and an external library is not a trivial problem.
When classdef is complete, the work will start, not finish. And classdef is already working on the development version, so if you are interested in those classes, you could start implementing them there and they'd be released with the next version. To continue development of classdef, Octave needs that people it, so that it's problems can be found. And the delaunayTriangulation class requires classdef. It looks like a great pair, that should be developed together.
After quite a bit of searching and trying different things, I am stumped on how to get mym to work (as found here: http://sourceforge.net/projects/mym/). I was wondering if anyone has a very simple list of actions needed to get this to work. I think my main trouble is installing zlib. I don't understand how to actually install it or work with it. I have tried to use Microsoft Visual C++ Express 2010 but then only the debug versions are compiled. That means when I try to use the mex function in matlab it gives me the error:
Error: Could not detect a compiler on local system
which can compile the specified input file(s)
I just don't understand the process and everywhere I look it says something different. I have tried multiple versions of each all of the programs involved and nothing seems to work. Any help would be greatly appreciated.
Do:
mex -setup
from the command line to define your compiler on your system. Once you do that then Matlab will correctly locate the compiler and build the mex libraries it needs.
See:
http://www.mathworks.com/help/matlab/matlab_external/building-mex-files.html
I need to use the CobraToolbox for a course and I am wondering if it is compatible with Octave.
Even googling for this doesn't return much results..
Thanks in advance
Unless someone has published their results, you can't know without trying it. However, there is a very high likelihood that it will work on Octave, here's what Jordi has to say on this issue answering this question.
I am new to Octave and was wondering if it is possible to use matlab
toolboxes in Octave?
It depends on what you mean by "Matlab toolbox". If you mean the code
that came with Matlab, it's probably a license violation to use it
with Octave, assuming you can compile it for Octave when it's
necessary to compile.
If you mean free code out there you found on the internet that was
written for Matlab, it is likely it will work on Octave. Just try it.
If you need to compile mex files, the "mkoctfile --mex" command may be
of use.
If you want to have a rough equivalent of the Matlab toolboxes in
Octave, try the Octave-Forge packages:
My personal experience is that Octave has become extremely good at accepting Matlab code. I would hazard a guess that any time you spend setting up Octave and this toolbox will be worth it. Even the MEX files appear to have a portability mechanism. Unless they are using some very specific features like addpref for toolbox persistent data, it will slide right into Octave. Even if they are using the prefs, it could be modified to live in Octave.