Get started with WinDbg (kernel-mode)

2025-07-24

Windows Debugger (WinDbg) is a kernel-mode and user-mode debugger included in the Debugging Tools for Windows. This article provides exercises to help you get started with using WinDbg as a kernel-mode debugger.

To get WinDbg, see Download and install the Windows debugger (WinDbg).

Set up a kernel-mode debugging

A kernel-mode debugging environment typically has two computers, the host computer and the target computer. The debugger runs on the host computer, and the code being debugged runs on the target computer. The host and target are connected by a debug cable.

The Windows debuggers support the following types of cables:

Ethernet
USB 3.0
Serial (also called null modem)

For speed and reliability, you should use an Ethernet cable with a local network hub. The following diagram illustrates a host and target computer connected for debugging with an Ethernet cable:

Diagram showing host and target computers connected by using an Ethernet cable for debugging.

An option for older versions of Windows is to use a direct cable, such as a serial cable:

Diagram showing host and target computers connected by using a debug cable for debugging.

Start the process by following the setup procedure for your desired configuration:

To set up the host and target computers, see Set up kernel-mode debugging manually.
To connect a debugger to a Hyper-V virtual machine (VM), see Set up network debugging for a virtual machine host - Kernel debugging over network (KDNET).

Establish a kernel-mode debugging session

After you set up your host and target computer and connect them with a debug cable, you can establish a kernel-mode debugging session.

Continue with the instructions in the article you used for the setup process. For example, if you set up your host and target computers for debugging over an Ethernet cable for kernel-mode debugging, follow the instructions in Set up KDNET network kernel debugging automatically.

Start debugging with WinDbg

To get started with using WinDbg for the debugging session, follow these steps:

On the host computer, open WinDbg and establish a kernel-mode debugging session with the target computer.
Open the debugger documentation CHM (.chm) file by selecting Help > Contents.

The debugger documentation is also available online in the Debugging Tools for Windows. For more information, see Install the Windows debugger.
When you establish a kernel-mode debugging session, WinDbg might break into the target computer automatically. If WinDbg doesn't break in, select Debug > Break.
In the command line at the bottom of the WinDbg window, run the following commands:
1. Set the symbol path with the .sympath (Symbol Path) command.
```
.sympath srv*
```
  The output is similar to this example:
```
Symbol search path is: srv*
Expanded Symbol search path is: cache*;SRV*https://msdl.microsoft.com/download/symbols
```
  The symbol search path tells WinDbg where to look for symbol program database (PDB) files (.pdb). The debugger needs symbol files to obtain information about code modules, such as function names and variable names.
2. Run the .reload command so WinDbg starts finding and loading symbols files.
```
.reload
```

View a list of loaded modules with the lm command.

lm

The output is similar to this example:

0:000>3: kd> lm
start               end                 module name
fffff800`00000000   fffff800`00088000   CI            (deferred)
...
fffff800`01143000   fffff800`01151000   BasicRender   (deferred)
fffff800`01151000   fffff800`01163000   BasicDisplay  (deferred)
...
fffff800`02a0e000   fffff800`03191000   nt  (pdb symbols) C:\...\ntkrnlmp.pdb
fffff800`03191000   fffff800`03200000   hal (deferred)
...

Start the target computer running again with the g (Go) command.
```
g
```
Break in to the target computer again by selecting Debug > Break.

Run the dt (Display Type) command and examine the _FILE_OBJECT data type in the nt module:

dt nt!_FILE_OBJECT

The output is similar to this example:

0:000>0: kd> dt nt!_FILE_OBJECT
   +0x000 Type                 : Int2B
   +0x002 Size                 : Int2B
   +0x008 DeviceObject         : Ptr64 _DEVICE_OBJECT
   +0x010 Vpb                  : Ptr64 _VPB
   ...
   +0x0c0 IrpList              : _LIST_ENTRY
   +0x0d0 FileObjectExtension  : Ptr64 Void

Run the x (Examine Symbols) command and look at some of the symbols in the nt module:

x nt!\*CreateProcess\*

The output is similar to this example:

0:000>0: kd> x nt!*CreateProcess*
fffff800`030821cc   nt!ViCreateProcessCallbackInternal (<no parameter info>)
...
fffff800`02e03904   nt!MmCreateProcessAddressSpace (<no parameter info>)
fffff800`02cece00   nt!PspCreateProcessNotifyRoutine = <no type information>
...

Run the bu (Set Breakpoint) and bl (Breakpoint List) commands to set and check breakpoints:

Use the bu command and set a breakpoint at the Windows call into the MmCreateProcessAddressSpace routine. Then run the bl command and verify the breakpoint is set.
```
bu nt!MmCreateProcessAddressSpace
bl
```
The output is similar to this example:
```
0:000>0: kd> bu nt!MmCreateProcessAddressSpace
0: kd> bl
0 e fffff800`02e03904  0001 (0001) nt!MmCreateProcessAddressSpace
```
Enter g (Go) to let the target computer run.
```
g
```
The target computer breaks into the debugger when Windows calls the MmCreateProcessAddressSpace routine.

If the target computer doesn't break into the debugger immediately, perform a few actions on the target computer. For example, open Notepad and save a file.

View the stack trace with the .reload and k (Display Stack Backtrace) commands:

.reload
k

The output is similar to this example:

0:000>2: kd> k
Child-SP            RetAddr             Call Site
ffffd000`224b4c88   fffff800`02d96834   nt!MmCreateProcessAddressSpace
ffffd000`224b4c90   fffff800`02dfef17   nt!PspAllocateProcess+0x5d4
ffffd000`224b5060   fffff800`02b698b3   nt!NtCreateUserProcess+0x55b
...
000000d7`4167fbb0   00007ffd`14b064ad   KERNEL32!BaseThreadInitThunk+0xd
000000d7`4167fbe0   00000000`00000000   ntdll!RtlUserThreadStart+0x1d

Select View > Disassembly. Then select Debug > Step Over (or select F10).

Enter step commands a few more times as you watch the output in the Disassembly window.
Clear your breakpoint with the bc (Breakpoint Clear) command.
```
bc *
```
Enter g (Go) to let the target computer run.
```
g
```
To break in again, select Debug > Break, or select CTRL-Break.

View a list of all processes with the !process command:

!process 0 0

The output is similar to this example:

0:000>0: kd> !process 0 0
**** NT ACTIVE PROCESS DUMP ****
PROCESS ffffe000002287c0
    SessionId: none  Cid: 0004    Peb: 00000000  ParentCid: 0000
    DirBase: 001aa000  ObjectTable: ffffc00000003000  HandleCount: <Data Not Accessible>
    Image: System

PROCESS ffffe00001e5a900
    SessionId: none  Cid: 0124    Peb: 7ff7809df000  ParentCid: 0004
    DirBase: 100595000  ObjectTable: ffffc000002c5680  HandleCount: <Data Not Accessible>
    Image: smss.exe
...
PROCESS ffffe00000d52900
    SessionId: 1  Cid: 0910    Peb: 7ff669b8e000  ParentCid: 0a98
    DirBase: 3fdba000  ObjectTable: ffffc00007bfd540  HandleCount: <Data Not Accessible>
    Image: explorer.exe

Copy the address for a process, such as ffffe00000d52900, and view the process information with the !process command. Replace the <process-address> portion with the process address:

!process <process-address> 2

The output for the ffffe00000d52900 process shows the following threads in the process:

0:000>0:000>0: kd> !process ffffe00000d52900 2
PROCESS ffffe00000d52900
    SessionId: 1  Cid: 0910    Peb: 7ff669b8e000  ParentCid: 0a98
    DirBase: 3fdba000  ObjectTable: ffffc00007bfd540  HandleCount:
     Image: explorer.exe

        THREAD ffffe00000a0d880  Cid 0910.090c  Teb: 00007ff669b8c000
            ffffe00000d57700  SynchronizationEvent

        THREAD ffffe00000e48880  Cid 0910.0ad8  Teb: 00007ff669b8a000
            ffffe00000d8e230  NotificationEvent
            ffffe00000cf6870  Semaphore Limit 0xffff
            ffffe000039c48c0  SynchronizationEvent
        ...
        THREAD ffffe00000e6d080  Cid 0910.0cc0  Teb: 00007ff669a10000
            ffffe0000089a300  QueueObject

Copy the address for a thread, such as ffffe00000e6d080, and view the thread information with the !thread command. Replace the <thread-address> portion with the thread address:

!thread <thread-ddress>

The output for the ffffe00000e6d080 thread shows the following summary information:

0: kd> !thread ffffe00000e6d080
THREAD ffffe00000e6d080  Cid 0910.0cc0  Teb: 00007ff669a10000 Win32Thread: 0000000000000000 WAIT: ...
    ffffe0000089a300  QueueObject
Not impersonating
DeviceMap                 ffffc000034e7840
Owning Process            ffffe00000d52900       Image:         explorer.exe
Attached Process          N/A            Image:         N/A
Wait Start TickCount      13777          Ticks: 2 (0:00:00:00.031)
Context Switch Count      2              IdealProcessor: 1
UserTime                  00:00:00.000
KernelTime                00:00:00.000
Win32 Start Address ntdll!TppWorkerThread (0x00007ffd14ab2850)
Stack Init ffffd00021bf1dd0 Current ffffd00021bf1580
Base ffffd00021bf2000 Limit ffffd00021bec000 Call 0
Priority 13 BasePriority 13 UnusualBoost 0 ForegroundBoost 0 IoPriority 2 PagePriority 5
...

View all the device nodes in the Plug and Play device tree with the !devnode command:

!devnode 0 1

The output is similar to this example:

0:000>0: kd> !devnode 0 1
Dumping IopRootDeviceNode (= 0xffffe000002dbd30)
DevNode 0xffffe000002dbd30 for PDO 0xffffe000002dc9e0
  InstancePath is "HTREE\ROOT\0"
  State = DeviceNodeStarted (0x308)
  Previous State = DeviceNodeEnumerateCompletion (0x30d)
  DevNode 0xffffe000002d9d30 for PDO 0xffffe000002daa40
    InstancePath is "ROOT\volmgr\0000"
    ServiceName is "volmgr"
    State = DeviceNodeStarted (0x308)
    Previous State = DeviceNodeEnumerateCompletion (0x30d)
    DevNode 0xffffe00001d49290 for PDO 0xffffe000002a9a90
      InstancePath is "STORAGE\Volume\{3007dfd3-df8d-11e3-824c-806e6f6e6963}#0000000000100000"
      ServiceName is "volsnap"
      TargetDeviceNotify List - f 0xffffc0000031b520  b 0xffffc0000008d0f0
      State = DeviceNodeStarted (0x308)
      Previous State = DeviceNodeStartPostWork (0x307)
...

View the device nodes and their hardware resources with the !devnode command:

!devnode 0 9

The output is similar to this example:

0:000>...
        DevNode 0xffffe000010fa770 for PDO 0xffffe000010c2060
          InstancePath is "PCI\VEN_8086&DEV_2937&SUBSYS_2819103C&REV_02\3&33fd14ca&0&D0"
          ServiceName is "usbuhci"
          State = DeviceNodeStarted (0x308)
          Previous State = DeviceNodeEnumerateCompletion (0x30d)
          TranslatedResourceList at 0xffffc00003c78b00  Version 1.1  Interface 0x5  Bus #0
            Entry 0 - Port (0x1) Device Exclusive (0x1)
              Flags (0x131) - PORT_MEMORY PORT_IO 16_BIT_DECODE POSITIVE_DECODE
              Range starts at 0x3120 for 0x20 bytes
            Entry 1 - DevicePrivate (0x81) Device Exclusive (0x1)
              Flags (0000) -
              Data - {0x00000001, 0x00000004, 0000000000}
            Entry 2 - Interrupt (0x2) Shared (0x3)
              Flags (0000) - LEVEL_SENSITIVE
              Level 0x8, Vector 0x81, Group 0, Affinity 0xf
...

View a device node that has a service name of "disk" with the !devnode command:

!devnode 0 1 disk

The output is similar to this example:

0: kd> !devnode 0 1 disk
Dumping IopRootDeviceNode (= 0xffffe000002dbd30)
DevNode 0xffffe0000114fd30 for PDO 0xffffe00001159610
  InstancePath is "IDE\DiskST3250820AS_____________________________3.CHL___\5&14544e82&0&0.0.0"
  ServiceName is "disk"
  State = DeviceNodeStarted (0x308)
  Previous State = DeviceNodeEnumerateCompletion (0x30d)
...

The output of the !devnode 0 1 command shows the address of the physical device object (PDO) for the node.

Copy the address of a PDO, such as 0xffffe00001159610, and view the PDO details with the !devstack command. Replace the <PDO-address> portion with the PDO information:
```
!devstack <PDO-address>
```
The output for the PDO 0xffffe00001159610 thread shows the following device stack:
```
0:000>0: kd> !devstack 0xffffe00001159610
  !DevObj           !DrvObj            !DevExt           ObjectName
  ffffe00001d50040  \Driver\partmgr    ffffe00001d50190  
  ffffe00001d51450  \Driver\disk       ffffe00001d515a0  DR0
  ffffe00001156e50  \Driver\ACPI       ffffe000010d8bf0  
```

Get information about the disk.sys driver object with the !drvobj command and the driver name "disk":

!drvobj disk 2

The output shows detailed information about the driver object:

0:000>0: kd> !drvobj disk 2
Driver object (ffffe00001d52680) is for:
 \Driver\disk
DriverEntry:   fffff800006b1270 disk!GsDriverEntry
DriverStartIo: 00000000
DriverUnload:  fffff800010b0b5c CLASSPNP!ClassUnload
AddDevice:     fffff800010aa110 CLASSPNP!ClassAddDevice

Dispatch routines:
[00] IRP_MJ_CREATE                      fffff8000106d160    CLASSPNP!ClassGlobalDispatch
[01] IRP_MJ_CREATE_NAMED_PIPE           fffff80002b0ab24    nt!IopInvalidDeviceRequest
[02] IRP_MJ_CLOSE                       fffff8000106d160    CLASSPNP!ClassGlobalDispatch
[03] IRP_MJ_READ                        fffff8000106d160    CLASSPNP!ClassGlobalDispatch
...
[1b] IRP_MJ_PNP                         fffff8000106d160    CLASSPNP!ClassGlobalDispatch

The output of the !drvobj command shows addresses of dispatch routines, such as CLASSPNP!ClassGlobalDispatch. Set and verify a breakpoint at the ClassGlobalDispatch routine with the following commands:
```
bu CLASSPNP!ClassGlobalDispatch
bl
```
Enter g (Go) to let the target computer run.
```
g
```
The target computer breaks into the debugger when Windows calls the ClassGlobalDispatch routine.

If the target computer doesn't break into the debugger immediately, perform a few actions on the target computer.or example, open Notepad and save a file.

View the stack trace with the following commands:

.reload
k

The output is similar to this example:

2: kd> k
Child-SP          RetAddr           Call Site
ffffd000`21d06cf8 fffff800`0056c14e CLASSPNP!ClassGlobalDispatch
ffffd000`21d06d00 fffff800`00f2c31d volmgr!VmReadWrite+0x13e
ffffd000`21d06d40 fffff800`0064515d fvevol!FveFilterRundownReadWrite+0x28d
ffffd000`21d06e20 fffff800`0064578b rdyboost!SmdProcessReadWrite+0x14d
ffffd000`21d06ef0 fffff800`00fb06ad rdyboost!SmdDispatchReadWrite+0x8b
ffffd000`21d06f20 fffff800`0085cef5 volsnap!VolSnapReadFilter+0x5d
ffffd000`21d06f50 fffff800`02b619f7 Ntfs!NtfsStorageDriverCallout+0x16
...

Use the qd (Quit and Detach) command to end your debugging session.
```
qd
```

Summary of commands

The following links provide more information about the commands described in this article.

For more information about menu commands like Debug > Break and Help > Contents, see the Get started with WinDbg (user-mode) article.

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Get started with WinDbg (kernel-mode)

Set up a kernel-mode debugging

Establish a kernel-mode debugging session

Start debugging with WinDbg

Summary of commands

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