New Debugging Book – Windows Debugging Notebook: Essential User Space WinDbg Commands

A reference book for technical support and escalation engineers troubleshooting and debugging complex software issues. The book is also invaluable for software maintenance and development engineers debugging Windows applications and services.   Do you want to know more about this book? Check out here…

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Special Command—Using .dump/.dumpcab to Get Dumps and Symbols from Production Servers

Using WinDbg you can create a dump file from an application running, for instance, in a production server. After collecting the dump file, you can load it in another machine and debug it. However, to be more effective during your debugging session you need symbols. Thus, thinking about it, here’s the trick to get both dump…

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Special Command—Using !chksym/!itoldyouso to Check PDB Files Against Modules

These are two debugger extensions that are used to see the PDB file that matches a specific module. Note that !itoldyouso is not documented. The output of both commands is identical.   Usage:   0:025> !chksym ntdll   ntdll.dll     Timestamp: 49EEA706   SizeOfImage: 180000           pdb: wntdll.pdb       pdb sig: E06BEA15-5E97-48BE-A818-E2D0DD2FED95           age: 2…

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Special Command—Using !for_each_frame to Run Commands

!for_each_frame is a favorite among debuggers. It’s a very flexible and powerful command that enables you to run commands for each frame of the call stack. You can use basically any command.  For instance, let’s say you want to see all local variables from each frame of a specific stack. Of course, to see local variables…

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Special Command—Peeking Memory Addresses Using !address

Let’s say that you get a memory address and you want to know if it’s from the heap, the stack, or someplace else. Or yet, let’s say you have a .NET application consuming lots of memory, and you want to get a better understanding of this memory consumption. The !address command is helpful in both situations…

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Special Command—Parsing Strings, Files, and Commands Output Using .foreach

  This is by far one of the most powerful WinDbg commands. Even if you don’t create scripts, you’ll benefit from this command.  It’s powerful because it’s flexible. You can use it for a huge variety of operations.   The .foreach token parses the output of one or more debugger commands and uses each value…

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Special Command—Parsing Commands Using .shell

Finally I’m writing about this command. I love it! It’s so powerful! .shell command launches a shell process and redirects its output to the debugger or to a specified file. Usage: .shell [Options] [ShellCommand] .shell -i InFile [-o OutFile [-e ErrFile]] [Options] ShellCommand  According to the WinDbg help, options can be: -ci “Commands” Processes the specified debugger commands and then passes their output as an…

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[PowerShell Script] Downloading PDB for Specific Modules

A few weeks ago, during a laboratory with a customer, I found myself struggling to download the public symbol from a specific driver. Since driver is Kernel Mode if you get a User Mode dump from the application using the driver, you won’t be able to actually see and download the driver. If you have…

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Special Command—Listing the Nearest Symbols with ln

ln is a very useful command. It stands for list nearest. You provide an address as argument, and it gives you the closest symbol that matches the address. Of course, you have to be using the right symbols!   Here is the syntax:   ln [address]   Example:       Tip: You can see…

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Special Command—Extracting Class and Struct Fields Using dt

dt is another command used almost all the time whenever you want to get the fields and type for a structure or class. For example, you may have a this pointer and use dt to get its fields and type. It’s a simple command with interesting variations that you should be aware of, because it’s…

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