I was wondering how I can tell if the Octave is busy doing something, or free and ready to accept new commands. There is no message on statue bar, or any other type of indicator.
For now I'm using disp("Busy..."); at the beginning of m-file and disp("Done"); or beep() at the end of m-file to see when the calculation is finished.
Thank you very much.
Related
I'm new to octave (and any kind of programing in general). It doesn't matter the code that I run, every time i do it the command window displays every line of it and every step, which can get overwhelming when doing cyclical algorithms. And this doesn't seem to happened to every other user I personally know. Even using exactly the same .m file, i get all the lines displayed and some other person doesn't.
I've searched in every configuration window possible, I tried reinstalling but nothing helped. And I've seen nobody else having this problem, is it just a configuration that I'm not aware of?
I'm running Octave 5.2.0 in Linux Mint 19.3
have you tried adding ";" at the end of your command lines ?
Basically if your code is something like:
x=5
y=4
Then your command window will display:
x=5
y=4
Whereas if you add the semicolons at the end of your code like so:
x=5;
y=4;
Then your values will be store and registered but nothing will be displayed in the command window.
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.
I am debugging an exe (x86) in WinDbg because it is crashing on my computer, the devs provide no support and it's closed source.
So far I found out that it crashes because a null pointer is passed to ntdll!RtlEnterCriticalSection.
I'm trying to find the source of that null pointer and I've reached a point (my "current point") where I have absolutely no idea where it was called from. I tried searching the area of the last few addresses on the stack, but there were no calls, jumps or returns at all there.
The only thing I have is the last dll loaded before the crash, which is apparently also long (at least a few thousand instructions) before my current point.
I can't just set a few thousand break points, so I thought single step exceptions could help (I could at least print eip on every instruction, I don't care if that would take days).
But I can't get the CPU to fire the exception! After loading the exe, I enter the following in the debugger:
sxe ld:<dll name>
g
sxe sse
sxe wos
r tf=1
g
The debugger breaks for the loaded dll where I want it to, but after the second g, the program just runs for a few seconds before hitting the crash point, not raising any single step exception at all.
If I do the same without the first two lines (so I'm at the start point of the program), it works. I know that tf is set to zero every time a SSE is fired, but why doesn't it fire at all later in the program?
Am I missing something? Or is there any other way I could find the source of that null pointer?
g is not the command for single stepping, it means "go" and only breaks on breakpoints or exceptions.
To do single stepping, use p. Since you don't have the source code, you cannot do instruction-stepping on source code level, meaning that you have to do it on assembly level. (Assembler instruction stepping should be default, it not enable it with l-t.) Depending on how far you need to go, this takes time.
Above only answers the question as it is. The open question is, like pointed out in the comments already, what will you do to mitigate that bug? You can't simply create a new critical section nor do you know which existing critical section should be used in that place.
I try to analyze a dll file with my poor assembly skills, so forgive me if I couldn't achieve something very trivial. My problem is that, while debugging the application, I find the code I'm looking for only in debug session, after I stop the debugger, the address is gone. The dll doesn't look to be obfuscated, as many of the code is readable. Take a look at the screenshot. The code I'm looking for is located at address 07D1EBBF in debug376 section. BTW, where did I get this debug376 section?
So my question is, How can I find this function while not debugging?
Thanks
UPDATE
Ok, as I said, as soon as I stop the debugger, the code is vanished. I can't even find it via sequence of bytes (but I can in debug mode). When I start the debugger, the code is not disassembled imediately, I should add a hardware breakpoint at that place and only when the breakpoint will be hit, IDA will show disassembled code. take a look at this screenshot
You see the line of code I'm interested in, which is not visible if the program is not running in debug mode. I'm not sure, but I think it's something like unpacking the code at runtime, which is not visible at design time.
Anyway, any help would be appreciated. I want to know why that code is hidden, until breakpoint hit (it's shown as "db 8Bh" etc) and how to find that address without debugging if possible. BTW, could this be a code from a different module (dll)?
Thanks
UPDATE 2
I found out that debug376 is a segment created at runtime. So simple question: how can I find out where this segment came from :)
So you see the code in the Debugger Window once your program is running and as you seem not to find the verry same opcodes in the raw Hex-Dump once it's not running any more?
What might help you is taking a Memory Snapshot. Pause the program's execution near the instructions you're interested in to make sure they are there, then choose "Take memory snapshot" from the "Debugger" Menu. IDA will then ask you wether to copy only the Data found at the segments that are defined as "loder segments" (those the PE loader creates from the predefined table) or "all segments" that seem to currently belong to the debugged program (including such that might have been created by an unpacking routine, decryptor, whatever). Go for "All segments" and you should be fine seeing memory contents including your debug segments (a segment
created or recognized while debugging) in IDA when not debugging the application.
You can view the list of segements at any time by pressing Shift+F7 or by clicking "Segments" from View > Open subviews.
Keep in mind that the programm your trying to analyze might choose to create the segment some other place the next time it is loaded to make it harder to understand for you what's going on.
UPDATE to match your second Question
When a program is unpacking data from somewhere, it will have to copy stuff somewhere. Windows is a virtual machine that nowadays get's real nasty at you when trying to execute or write code at locations that you're not allowed to. So any program, as long as we're under windows will somehow
Register a Bunch of new memory or overwrite memory it already owns. This is usually done by calling something like malloc or so [Your code looks as if it could have been a verry pointer-intensive language... VB perhaps or something object oriented] it mostly boils down to a call to VirtualAlloc or VirtualAllocEx from Windows's kernel32.dll, see http://msdn.microsoft.com/en-us/library/windows/desktop/aa366887(v=vs.85).aspx for more detail on it's calling convention.
Perhaps set up Windows Exception handling on that and mark the memory range als executable if it wasn't already when calling VirtualAlloc. This would be done by calling VirtualProtect, again from kernel32.dll. See http://msdn.microsoft.com/en-us/library/windows/desktop/aa366898(v=vs.85).aspx and http://msdn.microsoft.com/en-us/library/windows/desktop/aa366786(v=vs.85).aspx for more info on that.
So now, you should take a step trough the programm, starting at its default Entrypoint (OEP) and look for calls tho one of those functions, possibly with the memory protection set to PAGE_EXECUTE or a descendant. After that will possibly come some sort of loop decrypting the memory contents, copying them to their new location. You might want to just step over it, depending on what your interest in the program is by justr placing the cursor after the loop (thick blue line in IDA usually) and clicking "Run to Cursor" from the menu that appears upon right clicking the assembler code.
If that fails, just try placing a Hardware Breakpoint on kernel32.dll's VirtualAlloc and see if you get anything interestin when stepping into the return statement so you end up wherever the execution chain will take you after the Alloc or Protect call.
You need to find the Relative Virtual Address of that code, this will allow you to find it again regardless of the load address (pretty handy with almost all systems using ASLR these days). the RVA is generally calculated as virtual address - base load address = RVA, however, you might also need to account for the section base as well.
The alternative is to use IDA's rebasing tool to rebase the dll to the same address everytime.
as part of a homework assignment for my security class, I'm supposed to "add a simple function which prints "Hello, World!" to a compiled C Linux binary". The binary provided is just a compiled main function with 10 NOPs in it.
Normally, I would have written the code needed into the NOP section directly, but we were explicitly told to add a new function to the program.
I have no idea how to do that. I tried putting some code at the end of the binary, but this seems to destroy it. Could somebody clear this up for me?
EDIT: This question sounds somewhat similar.
EDIT 2: Searching for "ELF injection" yields many interesting results.
Perhaps you need to learn more about ELF (espacially if you want to make a program able to "infect" any Linux binary, not just the simple one you've got).
The Linux ABI X86-64 supplement could also be useful, and also the Linux Assembly Howto
You could end the main function, and then start a new function in the NOPs -- but before ending the main function, call the new function you have added after the end of the main function.