If you’re lucky, the thread that is racing with your crashing thread is still running on another processor. Maybe you’re not using a fast enough processor or the right BIOS version, but in any event, how can you tell what system configuration the customer is using from just a dump file? The asterisk are considered comment lines for $$<. The commands in this section are going to let you find out critical details about your system that just might be the clues you need to perform your analysis. Your feedback will help guide WinDbg's development going forward. 1. NOTE: The !vm output currently has a bug where the non-paged pool usage will always be listed as zero. In the WinDbg command line, input:.loadby sos clr Next, let’s run an analysis on the dump:!analyze … We then get to note the current usage of the system PTEs as well as the pools. Luckily, the debugger provides a quick way to identify the threads participating in the operation so that you can get right to resolving the issue. Post Your Comment, THREAD 8543cd48  Cid 0004.0b58  Teb: 00000000 Win32Thread: 00000000 READY, THREAD 85367020  Cid 0004.0008  Teb: 00000000 Win32Thread: 00000000 READY. …. For example, you can even query information about which RAM slots are populated using the smbios switch (e.g. As part of the Debugging Tools for Windows, WinDbg is a very known debugging tool that can use for both live and postmortem debug, user and kernel mode with a graphical user interface.. They’re difficult to track, difficult to reproduce, and when you get a crash it may be too late. !verifier 0x80 Address – This command dumps the allocate and free log, which logs each pool allocate and free made by your driver.  Free System PTEs: 231247 ( 924988 Kb) We can also see what happens if we specify a virtual address that isn’t valid to the hardware, such as one with its backing page currently in transition: contains 9B441863       contains 8B5A0860. !sysinfo smbios –memory). Included in the output is the call stack of the operation, which can be invaluable when you’re trying to track down use after free or double free bugs. WinDBG has a couple of commands that can make you feel like you’ve won the lottery and pinpoint the racing thread with ease. From WinDbg's command line do a !heap -p -a , where is the address of your allocation ***. ... 1    f7867120  86fb5b30            ............... f7a1eba0 f6c0d445 portcls!CIrpStream::GetMapping+0x17, f7a1ebc8 f6c31ce1 portcls!CPortPinWavePci::GetMapping+0x2a. Note: If the installation location for your instance of WinDBG is different, replace everything in front of cd in the command line above with the actual installation location of WinDBG in your case. ?\C:\pagefile.sys The EXCEPTION_RECORD field shows the excep… It helps Developers find and resolve errors in their … And, as luck would have it, if you enable Driver Verifier handle tracing is automatically turned on for the System process. User Comments You can look for the thread in the windbg Processes and Threads number or do it from the command window: First, list all threads: ~* Then, find the thread of interest, look for the thread ID of interest, and switch to it. Few developers know or understand the “old school” way of troubleshooting to uncover additional details; enter the WinDbg debugger.. WinDbg is a general-purpose debugger for Windows operating system applications and code. In this example, the debugger is attached to a user-mode application that has encountered an exception. Process Debug Server. Don’t be fooled by the name, the !vm command gives you a great quick view into the virtual and physical memory usage on a system. WinDbg cheat sheet for crash dump analysis. If the thread isn’t actively running, you might think that you would have to go the long way and try finding a racing thread with !process 0 7. As driver writers, however, we’re typically only interested in kernel handles. Race conditions are the worst. This is where !running comes in, which will show you information about each thread that is currently running on a processor in the system. In the WinDbg window, just to the left of the command line, notice the processor and thread numbers.  PagedPool Maximum: 51200 ( 204800 Kb) The debugger documentation is also available on line here. However, for those that might not be aware, !pool will take an arbitrary virtual address and let you know if it is a pool allocation or not. Enter !sysinfo, a command that can tell you just about anything you’d want to know about your system using information cached on the target. 1. !pnptriage is a nifty command that combines the output of several PnP related debugging commands. Thus, as long as Driver Verifier is enabled on the target you can dump the handle tracing log for all kernel handles with !htrace 0 PEPROCESS: Thread ID = 0x00000ab4, Process ID = 0x00000408, 0x828cef7b: nt!ExpWorkerFactoryCreateThread+0xFC, 0x828bf02e: nt!NtSetInformationWorkerFactory+0x56D, 0x82a97fde: nt!ObOpenObjectByPointerWithTag+0xC1, 0x82a98043: nt!ObOpenObjectByPointer+0x24, 0x82a9cdf0: nt!PspCreateObjectHandle+0x2E. In that case, you can use the !pte command, which will provide decoded information about a virtual address. On the File menu, choose Open Executable. The commands in this section are going to let you find out critical details about your system that just might be the clues you need to perform your analysis. to ask questions on Stack Overflow. You’re likely a developer and have used a code editor to debug and analyze your application failures. Well, what you might not realize is that starting in Windows Vista Verifier has been enhanced to keep a log of interesting events that happen in your driver. When used without any switches, !analyze simply returns the results of its analysis. In this case, an error message was displayed, indicating that either your machine was unable to access the internet or the web site was not working. Next, type the following into the elevated Command Prompt and press Enter:. You can analyze crash dump files by using WinDbg and other Windows debuggers. WinDbg Preview is using the same underlying engine as WinDbg today, so all the commands, extensions, and workflows you're used to will still work as they did before. ContentsDumping the StackDumping function argumentFinding nearest symbolFinding crash contextDumping the variables in Call stackDetermine the address of a symbolDumping the structureRelated Posts WinDbg support !analyze command for analyzing crash dump . For File name, enter notepad.exe. The actual non-paged pool usage is listed as, “NonPagedPoolNx Usage” in the output. BiosReleaseDate = 10/05/2001 Hot Network Questions How should we think about Spherical Harmonics? BiosVersion = A05 While !heap -p -a [UserAddr] will dump a call-stack, no source information will be included. kd> !pool 8539da40 2 When I use !pool, I like to specify a flags value of 2 to suppress information about other allocations surrounding the address (See Figure 4). 4. Optionally, the command takes an address value that will limit the output to only include allocation ranges including that address. On the Debug menu, choose Step Into (or press F11). WinDbg Preview is a new version of WinDbg with more modern visuals, faster windows, a full-fledged scripting experience, built with the extensible debugger data model front and center. Update Signature = REG_BINARY 0,0,0,0,2d,0,0,0 windbg ANSI Command Tree 1.0 title {"Window title"} body {"Group Heading"} {"Name of command to display"} {"command"} {"Name of command to display"} {"command… In the Open Executable dialog box, navigate to the folder that contains notepad.exe (for example, C:\Windows\System32). Here are a couple of commands that will get you the information that you need. Near the bottom of the WinDbg window, in the command line, enter this command: The symbol search path tells WinDbg where to look for symbol (PDB) files. For File name, enter MyApp.exe. Therefore it's good to have several versions of WinDbg available. Crash Dump Analysis Checklist. This command analyzes exception information in the crash dump, determines the place where the exception … We’re all using Driver Verifier, right? 3. Now WinDbg knows where to find symbols and source code for your application. Use WinDBG to Debug and analyze the screen dump, and then get to the root cause of the problem. SOSEX for .NET. From WinDbg's command line do a !heap -p -a [UserAddr], where [UserAddr] is the address of your allocation ***. Have an address and want to know what it is? ProcessorNameString = REG_SZ Intel(R) Pentium(R) 4 CPU 1.80GHz Thread commands not working in WInDbg. Unfortunately these facilities need to be turned on before the problem happens, but knowing that this information is available can be useful in some situations. However, some commands may make use of API calls that are not available and thus fail. Here’s some example output for a valid virtual address: contains 9B441863       contains 8B660121, pfn 9b441 ---DA--KWEV   pfn 8b660 -G--A--KREV. Can you count the number of WinDBG commands you know on one hand? Once you have enabled tracing via GFlags, you can view the trace for a given object with !obtrace(shown in Figure 5, page 29). ~MHz = REG_DWORD 1779 !poaction is the essential command for debugging any of your power related issues. The .cmdtree command allows to open a .txt file with predefined commands which you can simply double click to execute.. How to create command file. !verifier 0x200– This command dumps the critical region log, which logs each call to KeEnterCriticalRegion andKeLeaveCriticalRegion made by your driver. We will also assume that the application source code is in C:\MyApp\MyApp and that the target machine compiled MyApp.exe. However, WinDBG also provides us a way to look at threads that are ready to run, with the !ready command. ... We need to load SOS.dll or psscor2.dll for .NET 2.0 applications or psscor4.dll for .NET 4.0 applications into WinDbg for analyzing managed code. Install and configure WinDBG and the Symbols path to the correct Symbols folder. To set and verify a breakpoint at ZwWriteFile, enter these commands: Enter g to start Notepad running again.  Available Pages: 211575 ( 846300 Kb) BaseBoardVersion =. Remember what you've done and retain long outputs which can't be kept in WinDbg's buffer. Luckily, the O/S has built in facilities for logging handle and reference count activities. WinDbg is a kernel-mode and user-mode debugger that is included in Debugging Tools for Windows. The race has already happened and when the system crashes you’re dealing with the secondary failure, so there’s nothing that can be done, right? To see a list of code modules that are loaded in the Notepad process, enter this command: To see a stack trace, enter this command: To start Notepad running again, enter this command: To break in to Notepad, choose Break from the Debug menu. 2. Create Custom Command Window in Windbg. netext. Send me an email at ap@osr.comand let me know! For example: Navigate to your installation directory, and open WinDbg.exe. 2. In this example the current processor number is 0, and the current thread number is 11. MSR8B = REG_QWORD 2d00000000 kd> !sysinfo cpuinfo  Page File: \? Your application breaks in to the debugger when it comes to its main function. If you are connected to the internet, the debugger attempts to access a database of crash solutions maintained by Microsoft. Remote debugging through a process server involves running a small application called a process server on the server computer.  Physical Memory: 261886 ( 1047544 Kb) Example Documenting your work. The FAULTING_IP field shows the instruction pointer at the time of the fault. WinDbg displays your source code and the Command window.  NonPagedPool Max: 52691 ( 210764 Kb) Analyze crash dump files by using WinDbg. Great for getting insight into what’s going on when the system will mysteriously refuse to enter or resume from a lower power state: Flags..........: 80000004 OverrideApps|Critical, Allocated power irps (PopIrpList - 82978480), IRP: 8e1d8f00 (set/D0,), PDO: 89c0a248, CURRENT: 89fde028, IRP: 9d722e48 (set/D0,), PDO: 89c08818, CURRENT: 89f92620, IRP: 9fe7ee70 (set/D0,), PDO: 89c08940, CURRENT: 89f917a0. The most commonly used command is !analyze -v, which analyzes the current state of the program being debugged and the machine/process state at the moment of crash or hang. Is it a pool allocation? *** Virtual Memory Usage *** Object reference tracing, on the other hand, needs to be enabled on a system wide basis with GFlags. Now, start WinDbg on the debugger's side, invoke kernel debugging (Ctrl+K) to connect to the debuggee's machine (refer to for more information).   Pooltag Io : general IO allocations, Binary : nt!io. In many cases, WinDbg versions provided for newer Windows versions still work on older versions on Windows, e.g. Version 10 of WinDbg can still be used on Windows 7. In the Open Executable dialog box, navigate to the folder that contains notepad.exe (for example, C:\Windows\System32). Before moving on, I’d like to note something in the output here that often confuses people.  NonPagedPool Usage: 0 ( 0 Kb) WinDbg Preview is using the same underlying engine as WinDbg today, so all the commands, extensions, and workflows still work as they did before. When I run !vm I like to use a flags value of 0x21, which will omit some process specific memory usage information and add in some extra info about the kernel address space on platforms that support it (See Figure 1). Share your opinion with the community! The previous size value mentioned here is not the, “previous size of this allocation.” Instead, what it is telling you is the size of the allocation preceding this entry in the pool page. After you have installed the debugging tools, locate the installation directories for 64-bit (x64) and 32-bit (x86) versions of the tools. 2. Whenever using !ready, I like to use the 0xF flags value so that I can see the call stacks of the threads, though I won’t do that here just to keep the output short (see Figure 3). 1. setting a breakpoint in windbg using a script. We've updated WinDbg to have more modern visuals, faster windows, a full-fledged scripting experience, with the easily extensible debugger data model front and center. Here we provide hands-on exercises that will help you get started using WinDbg as a user-mode debugger. Assuming that you’ve enabled Driver Verifier on your driver, you can now extract valuable information with the following !verifier commands: Handle leaks and object reference leaks can be very tricky to track down, especially when working with a large code base. Patterns. For information about how to get Debugging Tools for Windows, see Debugging Tools for Windows (WinDbg, KD, CDB, NTSD). !verifier 0x100 Address – This command dumps the IRP log, which logs each call to IoAllocateIrp,IoCancelIrp, andIoCompleteRequest made by your driver. The O/S has some built in trace facilities that you can turn on to collect data that might be useful during analysis.  PagedPool Usage: 4904 ( 19616 Kb) Download WinDbg Preview from the Microsoft Store: WinDbg Preview. Here is how to use this command: cdb -z c:\myapp.dmp -logo out.txt -lines -c "!analyze -v;q" If I wanted to run !analyze and get the list of loaded modules, the following debugging script text file called, BasicAnalysis.txt, shows those commands. To look at the stack trace for thread 0, enter these commands: To quit debugging and detach from the Notepad process, enter this command: Suppose you have written and built this small console application. To analyze its contents, in the text field from the bottom of the Command panel, type !analyze -v and press Enter on your keyboard. [CPU Information] WinDbg on the debugger's side Find driver's address. For more information about remote sessions, see Remote Debugging Using WinDbg.  NonPagedPoolNx Usage: 2969 ( 11876 Kb) Template for VS. Python Scripting. and select Debug > Break. The running code breaks in when it comes to ZwCreateFile. 05/23/2017; 2 minutes to read; D; K; E; In this article. Handle tracing needs to be enabled on a per-process basis, which can be done by using Application Verifier. Navigate to your installation directory, and open WinDbg.exe. Identifier = REG_SZ x86 Family 15 Model 1 Stepping 2 The output is similar to this: WinDbg displays an analysis of the problem (division by 0 in this case). When you step into the line y = x / p2, your application will crash and break in to the debugger. Processes are the fundamental blocks of windows operating system. 3. Analyst’s Perspective is a column by OSR Consulting Associate, Scott Noone. Got your own favorite command that wasn’t represented here? How about the BIOS version and other platform info? CMDTREE.TXT for .cmdtree WinDbg command corresponding to Crash Dump Analysis Checklist. This command loads the SOS debugger extension for Windbg and basically helps Windbg understand how the memory is structured in managed programs, such as.NET applications, it provides detail about the internal Common Language Runtime (CLR) environment. ‘File’) and you can also limit the tracing to only apply to a single process’ objects. BiosVendor = Dell Computer Corporation To see a list of all threads in the Notepad process, enter this command (the tilde): In this example, there are 12 threads with indexes 0 through 11. It will identify any of your devnodes with problems as well as dump out any PnP worker threads that are currently executing, which will give you the ability to quickly identify the threads in the system that might be of interest to you: ****************************************************, InstancePath is "USB\VID_0403&PID_6001\7&2363c875&0&1", Previous State = DeviceNodeUninitialized (0x301). Continue stepping until you have stepped into MyFunction. !vm Don’t be fooled by the name, the !vm command gives you a great quick view into the virtual and physical memory usage on a system. This command analyzes exception information in the crash dump, determines the place where the exception occurred, the call stack, and displays detailed report. 0. Most importantly, !poaction will show any outstanding query or set power operations and the driver to which they were sent, which can be used to quickly identify which devices are preventing the power operations from occurring. Sometimes you’d like to view the virtual memory structures for a given virtual address, such as the PDE and PTE. Whenever I run this command I like to specify the –ti switch, to include thread stacks in the output as well as idle threads: 0    f7857120  85ed2da8            ................ ba9be62c 805310dd nt!KiDispatchException+0x307, ba9be694 8053108e nt!CommonDispatchException+0x4d, ba9be6a4 f6cd768d nt!Kei386EoiHelper+0x18e, ba9be6b4 f6c0675a ks!KsReleaseIrpOnCancelableQueue+0x5b, ba9be758 f6c15264 portcls!CIrpStream::ReleaseUnmappingIrp+0xd0, ba9be780 f6c21760 portcls!UpdateActivePinCount+0xb, f6cd7553 10c2c95e portcls!CPortPinWavePci::DistributeDeviceState+0x4d. 2. In order to view any .Net objects in WinDbg, you have to load the SOS extension. This command is often able to debug the current problem in a completely automated fashion. Before using WinDbg to analyze the dump, try using Process-Monitor (SysInternals, freeware) to monitor your process's activity. ... This document describes the procedure used in order to analyze the .dmpfile that is created when the Cisco Jabber for Windows client crashes. Create the file using this template. Load the .NET 4 managed (as appropriate) code extension and SOS extension with the following commands: If you have feedback such as a feature that you really want to see or a bug that makes something difficult, use the Feedback Hub. WinDbg Extensions. Comments or suggestions for this or future Analyst’s Perspective columns can be addressed to ap@osr.com. Wrong! CPUID1 = REG_BINARY 12,f,0,0,8,8,1,0,0,0,0,0,ff,fb,eb,3f. As is often the case, it worked on my machine and only manifested itself in production on a live site. Component Information = REG_BINARY 0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0 While !heap -p -a will dump a call-stack, no source information will be included. Its goals is to automatic analyze failures, detecting and assigning to known problems of … SystemManufacturer = Dell Computer Corporation if it fails because of a file system related issue, you can see exactly what caused the problem and what exactly it tried to do before failing. 1. BaseBoardProduct = OptiPlex GX400 Do you have a customer that can repeatedly reproduce a problem but you just can’t reproduce it with the exact same procedure? Note here that we see the amount of physical memory in the system as well as how much memory is currently free. Sometimes as part of your analysis, you’d like a bit more detailed information about the target system that generated the crash dump. If we suspect some sort of resource exhaustion going on in the system, we can use this command to quickly pinpoint which resource is being consumed. Running the !analyze -v command in WinDbg Preview to interpret the dump file. Update Status = REG_DWORD 0 Windbg Type Casting. Is it paged out? Probably what you want to do is switch to the owning thread and see what it's doing, why it's still holding the lock, etc. MEX Debugging Extension. Then a user-mode debugger is started on the client computer. Pool page 8539da40 region is Nonpaged pool !pool is a standard command for any toolbox, so I suspect that most of you know it and love it already.
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