I am running QEmu on Linux and the virtualized OS is Windows XP. I would like to have either the 1st or the 2nd possibility:
to apply a command in QEmu which creates a dump that can be opened with WinDbg
to apply a command in QEmu which creates a dump of a particular type and then use another utility to make it readable with WinDbg
I know about QEmu's "dump-guest-memory" (creates an ELF-dump), rekall's raw2dmp plugin and Volatility's raw2dmp plugin. The output can be scanned by WinDbg, but in fact you face the problem of a bad header - probably, the most important part of a dump, which is good for nothing when the dump was created using tools/plugins mentioned above. Many fields are lacking in correct details. Comparing to a normal dump created by Windows OS itself (for example, when crashing), which contains information which is full and correct.
I am a student and I got the task to resolve this problem. I think it is reasonable to ensure that it has not been completed yet by anybody so doing it does make sense.
if Qemu Monitor commands are acceptable set the crashonctrlscroll registry key in the guest os
set the dump creation parameters in SystemApplet
Mycomputer->properties->Advanced->Startup and Recovery->Settings->Complete memory dump)
path , no overwrite , uncheck automatically restart
and from Qemu monitor shell use sendkeys ctrl_r-scroll_lock-scroll_lock
that will generate a dump that will be windbg compatible
manually initiated_crash bugcheck code 0xe2
screen shot of a 700 mb ram xp64 guest os running inside qemu on a 32 bit xp32 os
Related
I have a custom windows kernel driver I have compiled. I sign it with a test cert, create the cat file from the cdf, stamp the inx into a inf file, then load it with pnputil. I then create a software device with SwDeviceCreate so the OS will pair my driver and the driver. This works fine.
The problem is if i screw up something in the compilation and get something like an error code 39 (viewable in device manager), I do not see that error. Instead the OS seems to try to fix the error by loading the previously working version of the driver. In order to see that error, I have to purge the driver and device using pnputil /d oem42.inf along with a pnputil /remove-device, then restart my PC, that seems to fix the issue. This is difficult because it means i have to restart my PC every time i run a test. I know crashing a kernel driver can cause a panic anyway and cause me to restart, but there seems to be instances where this is not the case and the OS tries to rectify the issue without me (as it probably should).
So my question is this. Is there a way to completely purge my driver without a complete restart in-between installations/tests so I can correctly break it. I know I am suppose to use another machine and remote debug kernel drivers, but i do not have access to another machine right now that can support windows 11.
I'm developing a program running on embedded Linux (Debian Buster), and I found the program sometimes has performance issues. After some debugging process, I doubt the issue might not be in my program. Instead, somehow the OS start doing memory swap and my program was swapped to the file system.
Therefore, I use the code here to verify. And it turns out my program occupied much less physical memory after about 500 seconds, and it matches the hypothesis.
Now I want to find which process suddenly takes lots of memory at that point, but I don't know how.
Is there anyway to keep monitoring memory usage of all processes (or the top 10) of the system and dump to a log file? Any tools or commands would be good.
Thanks.
I'm developing a program running on embedded Linux
It will be helpful, if you could specify which embedded Linux you are working on.
Based on that, there are tools that someone could suggest.
For Linux, I would say, you could use:
top -p [PID]
you can get PID by:
ps [options]
I am not sure if there is a problem while using the command line?
dump to a log file
I think you could use grep to dump the terminal output to a log file you can create using touch command.
I am trying to write a simple OS, I already wrote a bootloader but now I want to debug it, so I switched from using VirtualBox to QEMU because I saw it had better debugging.
The problem is that after I added the -s parameter to QEMU command and successfully connected via GDB, it says that the symbol table isn't loaded and that I should use the "file" command.
The only difference from what I did to what I saw people on the Internet do, is that they started GDB with gdb vmlinux, but I can't do that because I am not debugging a Linux kernel... so I figured that the issue is that I didn't start GDB with an executable, but using the "file" command on my OS image, and the compiled and linked .out file, tells me it's a "DOS/MBR boot sector", so I can't start GDB with either of them (I tried to do that anyways, but GDB failed).
Help would be appreciated.
EDIT: also, I did assemble the bootloader with the -g and --gstabs+ options.
gdb would like a file so that it can give you symbolic debugging information. For that you will need to give it a file in a format with debug info which corresponds to where your OS ends up in RAM. The "DOS/MBR boot sector" file is a disk image (the BIOS will load part of this into RAM for you, and it will then presumably finish loading code itself).
But gdb will also entirely happily let you do assembly-level debugging; you can just ignore the warning about not having a symbol table, and use the single step instruction, disassemble-from-pc and similar commands:
"disas $pc,+32" disassembles 32 bytes from the current PC
the display command prints after execution stops, so "disp /3i $pc" will print the next 3 instructions every time gdb gets control
"stepi" and "nexti" do single-instruction step/next ("step" and "next" are source-line stepping and require debug info)
I tried to learn "Lena's reversing for newbies", when some trouble arise.
I start Pixtopian Book with ollyDbg, then try to have MessageBox with message about uregistered version.
Then i switch to OllyDbg, stop program executing and press "Alt+F9" for "Back to user mode" which stop the program after it exit from DLL.
But after this program does not work, it's frozen and does not respond to my actions.
If i turn off "Back to user mode" program normally work.
What's the problem? Can i try to use "Back to user mode" in IDA (uses WinDbg) or some other debugger and How i can do this? Can i repair it function in OllyDbg?
P.S. It's like the program stopped and didn't run after use "ALT+F9".
/Sorry for my English, i'm just learning ;-)/
First of all, Ollydbg is meant for 32 bit platform. It means that it will run only on a 32 bit OS and can only debug 32 bit apps.
In x64 Operating Systems (specifically Windows) there is a feature called compatibility mode that lets you run 32 bit apps. The 32 bit code is either run by emulation or natively (when the hardware itself implements the instruction set and then it is called x86-64).
So, when you try to run Ollydbg in a x64 environment it will run, but you will experience problems like the one you are facing. It occurs because Ollydbg is run in an emulation mode. Being a debugger it needs access to the registers and other system structures, which it is denied. What it can see is a virtual image of the system.
So the solution to the problem is using a Virtual Machine.
You would install a 32 bit OS in it and debug the app using Ollydbg. As far as Virtual Machines are concerned, I would recommend VMWare. You can use either the workstation or player version. The latter is free but does not support snapshots.
Other solutions are Virtual Box, Parallels Workstation and Microsoft Virtual PC.
The disadvantages of them are that Virtual Box does not support hardware breakpoints, Parallels Workstation is no longer supported as of 2014 and moreover there you would get a BSOD if you try to single step through FPU instructions. I have not tested Virtual PC though.
Note : Ollydbg does not supports x64 but its author is working on a x64 version.
I just learned how to update changes to the exe file for ollydby v 2.01e.
suppose I wished to change a jl command to a jmp; do this by clicking the executable modules button, choose the file and right click to view the file. then record the changes and save file. The saved file also has a backup in case something goes wrong.
I just did a thorough learning of the pixtopian file. When I downloaded
that tutorial I get the file pixtopian107.exe only. Since it didn't agree with the tutorial I investigated further. That file is an installation file. It produces a regular pixtopian.exe file which is the file you wish to play with.
I also noticed that in running the file it never enters the main module.
this is because of the TLS callback. right now I am trying to learn how
to overcome this which is how i came to this site in the first place.
I am using ollydbg vs2.01e very effectively.
Another thing, in vs 2.01e I am still trying to save changed data. Until I succeed I am recording the changes in the exe files using hex editor.
From my experience I can tell that this functionality won't work on Windows 7.
On Windows 7 64bit --> Won't work at all.
On Windows 7 32bit --> Will work partially, but only when using option "File>Attach" in OllyDbg.
For me, best solution was to use Windows XP 32bit, then it worked fine.
I have recently started windows driver development. I am wondering how does it actually debug my driver. The setup I have is --> Win7 as host, XP as guest on VMware, and I am debugging through serial port.
The research I have done:
I found only this link saying very few things that I am talking about.
I already know how debugger works on single OS, in that case debugger is also on the same OS, so it knows which process is running. That is understandable. But here, debugger is on entirely different OS, an entirely different environment. I just say file->open source files and I AM able to put breakpoints!! Moreover when I load driver, it actually breaks there. I mean why../How? How does XP's kernel comes to know(drivers are extension to kernel, atleast WDM, don't know about WDK) that there is source code of this driver? and that also outside its control(environment)? I mean I can have 10 files open with breakpoint in them, but it works beautifully, I am not able to fail/fool it.
So what I am thinking is like, whenever we add source to windbg on Win7, it creates the binary from that source, and whenever XP is going to load any binary, it checks if this is the binary that windbg is waiting for. what is confusing in above link is, Vikrant is saying that debugger asks kernel(XP) that it is willing to debug a process --> Bus HELLO... process is running on XP, and windbg on Win7 and does not know name or id of process. It has source code, but consider a case where there is a driver which is build out of 300 files, and just one, probably simplest file is open in windbg, how it matched that this source code is of the driver being run?
#Kjelll answer is correct. Here is the full scenario, including explanation to your comment:
PDB files have line information. This is a mapping from each (file,line) location to address (RVA - relative virtual address).
When you set a break point on a source file, WinDBG checks whether this source file correspond to a current address. If it is - it sets the breakpoint. Otherwise, it becomes a "future breakpoint" (not sure whether Microsoft uses this terminology).
When a new binary is a loaded, the agent on the client communicates with the host, informs it about the binary. At this point - WinDBG will try to allocate a PDB file.
WinDBG will start at the PDB location embedded within the file. You can see this value by using this command line: windbg -dump -pdbpath xxx.sys. This should explain how WinDBG will find a symbol file even if not on the .sympathy path (that I believe answers your comment to Kjell).
WinDBG will then search at the .sympathy.
Once symbol is find, it will look at all future breakpoint, and if applicable will set an actual breakpoint.
I think your link explain your question pretty well, but you have probably not realized what the mechanism of the pdb do for the debugger. The windbg on your host OS uses the pdb file to translate line nubers in the source files to addresses in your guest OS (xp) . Then the the debugger agent uses this address to set break points (Int 3) in the guest OS.This is much in the same way as a local debugger do to a local process.