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Common WinDbg Commands (Thematically Grouped)



1) Built-in help commands
Cmd Variants / Params Description

?

?
? /D

Display regular commands
Display regular commands as DML

.help

.help
.help /D
.help /D a*

Display . commands
Display . commands in DML format (top bar of links is given)
Display . commands that start with a* (wildcard) as DML

.chain

.chain
.chain /D

Lists all loaded debugger extensions
Lists all loaded debugger extensions as DML (where extensions are linked to a .extmatch)

.extmatch

.extmatch /e ExtDLL FunctionFilter
.extmatch /D /e ExtDLL FunctionFilter

Show all exported functions of an extension DLL. FunctionFilter = wildcard string
Same in DML format (functions link to "!ExtName.help FuncName" commands)

Example: .extmatch /D /e uext * (show all exported functions of uext.dll)

.hh

.hh
.hh Text

Open WinDbg's help
Text = text to look up in the help file index
Example: .hh dt

2) General WinDbg's commands (show version, clear screen, etc.)
Cmd Variants / Params Description

version

Dump version info of debugger and loaded extension DLLs

vercommand

Dump command line that was used to start the debugger

vertarget

Version of target computer

CTRL+ALT+V

Toggle verbose mode ON/OFF
In verbose mode some commands (such as register dumping) have more detailed output.

n

n [8 | 10 | 16]

Set number base

.formats

.formats Expression

Show number formats = evaluates a numerical expression or symbol and displays it in multiple numerical formats (hex, decimal, octal, binary, time, ..)
Example 1: .formats 5
Example 2: .formats poi(nLocal1) == .formats @@($!nLocal1)

.cls

Clear screen

.lastevent

Displays the most recent exception or event that occurred (why the debugger is waiting?)

.effmach

.effmach
.effmach .
.effmach #
.effmach x86 | amd64 | ia64 | ebc

Dump effective machine (x86, amd64, ..):
Use target computer's native processor mode
Use processor mode of the code that is executing for the most recent event
Use x86, amd64, ia64, or ebc processor mode

This setting influences many debugger features:
-> which processor's unwinder is used for stack tracing
-> which processor's register set is active

.time

display time (system-up, process-up, kernel time, user time)

3) Debugging sessions (attach, detach, ..)
Cmd Variants / Params Description

.attach

PID

attach to a process

.detach

ends the debugging session, but leaves any user-mode target application running

q

q, qq

Quit = ends the debugging session and terminates the target application
Remote debugging: q= no effect; qq= terminates the debug server

.restart

Restart target application

4) Expressions and commands
Cmd Variants / Params Description

;

Command separator (cm1; cm2; ..)

?

? Expression
?? Expression

Evaluate expression (use default evaluator)
Evaluate c++ expression

.expr


.expr
.expr /q
.expr /s c++
.expr /s masm

Choose default expression evaluator
Show current evaluator
Show available evaluators
Set c++ as the default expression evaluator
Set masm as the default expression evaluator

*

* [any text]

Comment Line Specifier
Terminated by: end of line

$$

$$ [any text]

Comment Specifier
Terminated by: end of line OR semicolon

.echo

.echo String
.echo "String"

Echo Comment -> comment text + echo it
Terminated by: end of line OR semicolon
With the $$ token or the * token the debugger will ignore the inputted text without echoing it.

5) Debugger markup language (DML)

Starting with the 6.6.07 version of the debugger a new mechanism for enhancing output from the debugger and extensions was included: DML.
DML allows output to include directives and extra non-display information in the form of tags.
Debugger user interfaces parse out the extra information to provide new behaviors.

DML is primarily intended to address two issues:
  • Linking of related information
  • Discoverability of debugger and extension functionality
Cmd Variants / Params Description

.dml_start

Kick of to other DML commands

.prefer_dml

.prefer_dml [1 | 0]

Global setting: should DML-enhanced commands default to DML?
Note that many commands like k, lm, .. output DML content thereafter.

.help /D

.help has a new DML mode where a top bar of links is given

.chain /D

.chain has a new DML mode where extensions are linked to a .extmatch

.extmatch /D

.extmatch has a new DML format where exported functions link to "!ExtName.help FuncName" commands

lmD

lm has a new DML mode where module names link to lmv commands

kM

k has a new DML mode where frame numbers link to a .frame/dv

.dml_flow



.dml_flow StartAddr TargetAddr

Allows for interactive exploration of code flow for a function.

  1. Builds a code flow graph for the function starting at the given start address (similar to uf)
  2. Shows the basic block given the target address plus links to referring blocks and blocks referred to by the current block
Example: .dml_flow CreateRemoteThread CreateRemoteThread+30

6) Main extensions
Cmd Variants / Params Display supported commands for ..

!Ext.help

General extensions

!Exts.help

-||-

!Uext.help

User-Mode Extensions (non-OS specific)

!Ntsdexts.help

User-Mode Extensions (OS specific)

!logexts.help

Logger Extensions

!clr10\sos.help

Debugging managed code

!wow64exts.help

Wow64 debugger extensions

!Wdfkd.help

Kernel-Mode driver framework extensions

!Gdikdx.help

Graphics driver extensions

..

!NAME.help



!NAME.help FUNCTION

Display detailed help about an exported function
NAME = placeholder for extension DLL
FUNCTION = placeholder for exported function

Example: !Ntsdexts.help handle (show detailed help about !Ntsdexts.handle)

7) Symbols
Cmd Variants / Params Description

ld

ld ModuleName
ld *

Load symbols for Module
Load symbols for all modules

!sym

!sym
!sym noisy
!sym quiet

Get state of symbol loading
Set noisy symbol loading (debugger displays info about its search for symbols)
Set quiet symbol loading (=default)

x

x [Options] Module!Symbol
x /t ..
x /v ..
x /a ..
x /n ..
x /z ..

Examine symbols: displays symbols that match the specified pattern
with data type
verbose (symbol type and size)
sort by address
sort by name
sort by size ("size" of a function symbol is the size of the function in memory)

ln


ln Addr

List nearest symbols = display the symbols at or near the given Addr. Useful to:

  • determine what a pointer is pointing to
  • when looking at a corrupted stack to determine which procedure made a call

.sympath

.sympath
.sympath+

Display or set symbol search path
Append directories to previous symbol path

.symopt

.symopt
.symopt+ Flags
.symopt- Flags

displays current symbol options
add option
remove option

.symfix

.symfix
.symfix+ DownstreamStore

Set symbol store path to automatically point to http://msdl.microsoft.com/download/symbols
+ = append it to the existing path
DownstreamStore = directory to be used as a downstream store. Default is WinDbgInstallationDir\Sym.

.reload

.reload
.reload [/f | /v]
.reload [/f | /v] Module

Reload symbol information for all modules**
f = force immediate symbol load (overrides lazy loading); v = verbose mode
Module = for Module only

**Note: The .reload command does not actually cause symbol information to be read. It just lets the debugger know that the symbol files may have changed, or that a new module should be added to the module list. To force actual symbol loading to occur use the /f option, or the ld (Load Symbols) command.

x *! list all modules
x ntdll!* list all symbols of ntdll
x /t /v MyDll!* list all symbol in MyDll with data type, symbol type and size
x kernel32!*LoadLib* list all symbols in kernel32 that contain the word LoadLib
.sympath+ C:\MoreSymbols add symbols from C:\MoreSymbols (folder location)
.reload /f @"ntdll.dll" Immediately reload symbols for ntdll.dll.
.reload /f @"C:\WINNT\System32\verifier.dll" Reload symbols for verifier. Use the given path.

Also check the "!lmi" command.
8) Sources
Cmd Variants / Params Description

.srcpath

.srcpath
.srcpath+ DIR

Display or set source search path
Append directory to the searched source path

.srcnoisy

{1|0}

Controls noisy source loading

.lines

[-e | -d | -t]

Toggle source line support: enable; disable; toggle

l (small letter L)

l+l, l-l
l+o, l-o
l+s, l-s
l+t, l-t

show line numbers
suppress all but [s]
source and line number
source mode vs. assembly mode

9) Exceptions, events, and crash analysis
Cmd Variants / Params Description

g

g
gH
gN

Go
Go exception handled
Go not handled

.lastevent

What happened? Shows most recent event or exception

!analyze

!analyze -v
!analyze -hang
!analyze -f

Display information about the current exception or bug check; verbose
User mode: Analyzes the thread stack to determine whether any threads are blocking other threads.
See an exception analysis even when the debugger does not detect an exception.

sx

sx
sxe
sxd
sxn
sxi
sxr

Show all event filters with break status and handling
break first-chance
break second-chance
notify; don't break
ignore event
reset filter settings to default values

.exr

.exr-1
.exr Addr

display most recent exception record
display exception record at Addr

.ecxr

displays exception context record (registers) associated with the current exception

!cppexr

Addr

Display content and type of C++ exception

exr -1 display most recent exception
.exr 7c901230 display exception at address 7c901230
!cppexr 7c901230 display c++ exception at address 7c901230
10) Loaded modules and image information
Cmd Variants / Params Description

lm

lm[ v | l | k | u | f ] [m Pattern]
lmD

List modules; verbose | with loaded symbols | k-kernel or u-user only symbol info | image path; pattern that the module name must match
DML mode of lm; lmv command links included in output

!dlls

!dlls
!dlls -i
!dlls -l
!dlls -m
!dlls -v
!dlls -c ModuleAddr
!dlls -?

all loaded modules with load count
by initialization order
by load order (default)
by memory order
with version info
only module at ModuleAddr
brief help

!imgreloc

ImgBaseAddr

information about relocated images

!lmi

Module

detailed info about a module (including exact symbol info)

!dh

!dh ImgBaseAddr
!dh -f ImgBaseAddr
!dh -s ImgBaseAddr
!dh -h

Dump headers for ImgBaseAddr
f = file headers only
s = section headers only
h = brief help

The !lmi extension extracts the most important information from the image header and displays it in a concise summary format. It is often more useful than !dh.

lm display all loaded and unloaded modules
lmv m kernel32 display verbose (all possible) information for kernel32.dll
lmD DML variant of lm
!dlls -v -c kernel32 display information for kernel32.dll, including load-count
!lmi kernel32 display detailed information about kernel32, including symbol information
!dh kernel32 display headers for kernel32
11) Process related information
Cmd Variants / Params Description

!dml_proc

(DML) displays current processes and allows drilling into processes for more information

| (pipe)

Print status of all processes being debugged

.tlist

lists all processes running on the system

!peb

display formatted view of the process's environment block (PEB)

!peb Dump formatted view of processes PEB (only some information)
r $peb Dump address ob PEB. $peb == pseudo-register
dt ntdll!_PEB Dump PEB struct
dt ntdll!_PEB @$peb -r Recursively (-r) dump PEB of our process
12) Thread related information
Cmd Variants / Params Description

~

~
~* [Command]
~. [Command]
~# [Command]
~Number [Command]
~~[TID] [Command]
~Ns

list threads
all threads
current thread
thread that caused the current event or exception
thread whose ordinal is Number
thread whose thread ID is TID (the brackets are required)
switch to thread N (new current thread)

[Command]: works for a few regular commands such as k, r

~e


~* e CommandString
~. e CommandString
~# e CommandString
~Number e CommandString

Execute thread-specific commands (CommandString = one or more commands to be executed) for:
all threads
current thread
thread which caused the current event
thread with ordinal

~f

~Thread f

Freeze thread (see ~ for Thread syntax)

~u

~Thread u

Unfreeze thread (see ~ for Thread syntax)

~n

~Thread n

Suspend thread = increment thread's suspend count

~m

~Thread m

Resume thread = decrement thread's suspend count

!teb

display formatted view of the thread's environment block (TEB)

!tls

!tls -1
!tls SlotIdx
!tls [-1 | SlotIdx] TebAddr

-1 = dump all slots for current thread
SlotIdx = dump only specified slot
TebAddr = specify thread; if omitted, the current thread is used

.ttime

display thread times (user + kernel mode)

!runaway

[Flags: 0 | 1 | 2]

display information about time consumed by each thread (0-user time, 1-kernel time, 2-time elapsed since thread creation). quick way to find out which threads are spinning out of control or consuming too much CPU time

!gle

!gle
!gle -all

Dump last error for current thread
Dump last error for all threads

Point of interest:
SetLastError( dwErrCode ) checks the value of kernel32!g_dwLastErrorToBreakOn and possibly executes a DbgBreakPoint.

if ((g_dwLastErrorToBreakOn != 0 ) && (dwErrCode == g_dwLastErrorToBreakOn))
DbgBreakPoint();

The downside is that SetLastError is only called from within KERNEL32.DLL.
Other calls to SetLastError are redirected to a function located in NTDLL.DLL, RtlSetLastWin32Error.

!error

!error ErrValue
!error ErrValue 1

Decode and display information about an error value
Treat ErrValue value as an NTSTATUS code

~* k call stack for all threads ~ !uniqstack
~2 f Freeze Thread TID=2
~# f Freeze the thread causing the current exception
~3 u Unfreeze Thread TID=3
~2e r; k; kd == ~2r; ~2k; ~2kd
~*e !gle will repeat every the extension command !gle for every single thread being debugged
!tls -1 Dump all TLS slots for current thread
!runaway 7 1 (user time) + 2 (kernel time) + 4 (time elapsed since thread start)
!teb Dump formatted view of our threads TEB (only some information)
dt ntdll!_TEB @$teb Dump TEB of current thread
13) Breakpoints
Cmd Variants / Params Description

bl

List breakpoints

bc

bc *
bc # [#] [#]

Clear all breakpoints
Clear breakpoint #

be

be *
be # [#] [#]

Enable all bps
Enable bp #

bd

bd *
bd # [#] [#]

Disable all bps
Disable bp #

bp

bp [Addr]
bp [Addr] ["CmdString"]

[~Thrd] bp[#] [Options] [Addr] [Passes] ["CmdString"]

Set breakpoint at address
CmdString = Cmd1; Cmd2; .. Executed every time the BP is hit.

~Thrd == thread that the bp applies too.
# = Breakpoint ID
Passes = Activate breakpoint after #Passes (it is ignored before)

bu

bu [Addr]

See bp ..

Set unresolved breakpoint. bp is set when the module gets loaded

bm

bm SymPattern
bm SymPattern ["CmdString"]

[~Thrd] bm [Options] SymPattern [#Passes] ["CmdString"]

Set symbol breakpoint. SymPattern can contain wildcards
CmdString = Cmd1; Cmd2; .. Executed every time the BP is hit.

~Thrd == thread that the bp applies too.
Passes = Activate breakpoint after #Passes (it is ignored before)

The syntax bm SymPattern is equivalent to using x SymPattern and then using bu on each of the results.

ba

ba [r|w|e] [Size] Addr

[~Thrd] ba[#] [r|w|e] [Size] [Options] [Addr] [Passes] ["CmdString"]

Break on Access: [r=read/write, w=write, e=execute], Size=[1|2|4 bytes]

[~Thrd] == thread that the bp applies too.
# = Breakpoint ID
Passes = Activate breakpoint after #Passes (it is ignored before)

br

br OldID NewID [OldID2 NewID2 ...]

renumbers one or more breakpoints


With bp, the breakpoint location is always converted to an address. In contrast, a bu or a bm breakpoint is always associated with the symbolic value.


Simple Examples
bp `mod!source.c:12` set breakpoint at specified source code
bm myprogram!mem* SymbolPattern is equivalent to using x SymbolPattern
bu myModule!func bp set as soon as myModule is loaded
ba w4 77a456a8 break on write access
bp @@( MyClass::MyMethod ) break on methods (useful if the same method is overloaded and thus present on several addresses)



Breakpoitns with options
Breakpoint that is triggered only once
bp mod!addr /1
Breakpoint that will start hitting after k-1 passes
bp mod!addr k



Breakpoints with commands: The command will be executed when the breakpoint is hit.
Produce a log every time the breakpoint is hit
ba w4 81a578a8 "k;g"
Create a dump every time BP is hit
bu myModule!func ".dump c:\dump.dmp; g"
DllMain called for MYDLL -> check reason
bu MYDLL!DllMain "j (dwo(@esp+8) == 1) '.echo MYDLL!DllMain -> DLL_PROCESS_ATTACH; kn' ; 'g' "
LoadLibraryExW( anyDLL ) called -> display name of anyDLL
bu kernel32!LoadLibraryExW ".echo LoadLibraryExW for ->; du dwo(@esp+4); g"
LoadLibraryExW( MYDLL ) called? -> Break only if LoadLibrary is called for MyDLL
bu kernel32!LoadLibraryExW ";as /mu ${/v:MyAlias} poi(@esp+4); .if ( $spat( \"${MyAlias}\", \"*MYDLL*\" ) != 0 ) { kn; } .else { g }"
  • The first parameter to LoadLibrary (at address ESP + 4) is a string pointer to the DLL name in question.
  • The MASM $spat operator will compare this pointer to a predefined string-wildcard, this is *MYDLL* in our example.
  • Unfortunately $spat can accept aliases or constants, but no memory pointers. This is why we store our string in question to an alias (MyAlias) first.
  • Our kernel32!LoadLibraryExW breakpoint will hit only if the pattern compared by $spat matches. Otherwise the application will continue executing.
Skip execution of a function
bu sioctl!DriverEntry "r eip = poi(@esp); r esp = @esp + 0xC; .echo sioctl!DriverEntry skipped; g"
  • Right at a function’s entry point the value found on the top of the stack contains the return address
    r eip = poi(@esp) -> Set EIP (instruction pointer) to the value found at offset 0x0
  • DriverEntry has 2x4 byte parameters = 8 bytes + 4 bytes for the return address = 0xC
    r esp = @esp + 0xC -> Add 0xC to Esp (the stack pointer), effectively unwinding the stack pointer
bu MyApp!WinMain "r eip = poi(@esp); r esp = @esp + 0x14; .echo WinSpy!WinMain entered; g"
  • WinMain has 4x4 byte parameters = 0x10 bytes + 4 bytes for the return address = 0x14


Howto set a brekpoint in your code programatically?
  • kernel32!DebugBreak
  • ntdll!DbgBreakPoint
  • __asm int 3 (x86 only)
14) Tracing and stepping (F10, F11)

Each step executes either a single assembly instruction or a single source line, depending on whether the debugger is in assembly mode or source mode.
Use the l+t and l-t commands or the buttons on the WinDbg toolbar to switch between these modes.
Cmd Variants / Params Description

g (F5)

g
gu

Go (F5)
Go up = execute until the current function is complete
gu ~= g @$ra
gu ~= bp /1 /c @$csp @$ra;g
-> $csp = same as esp on x86
-> $ra = The return address currently on the stack

p (F10)

p

pr
p Count
p [Count] "Command"
p =StartAddress [Count] ["Command"]

[~Thread] p [=StartAddress] [Count] ["Command"]

Single step - executes a single instruction or source line. Subroutines are treated as a single step.

Toggle display of registers and flags
Count = count of instructions or source lines to step through before stopping
Command = debugger command to be executed after the step is performed
StartAddress = Causes execution to begin at the specified address. Default is the current EIP.

~Thread = The specified thread is thawed and all others frozen

t (F11)

t
..

Single trace - executes a single instruction or source line. For subroutines each step is traced as well.

pt

pt
..

Step to next return - similar to the GU (go up), but staying in context of the current function
If EIP is already on a return instruction, the entire return is executed. After this return is returned, execution will continue until another return is reached.

tt

tt
..

Trace to next return - similar to the GU (go up), but staying in context of the current function
If EIP is already on a return instruction, the debugger traces into the return and continues executing until another return is reached.

pc

pc
..

Step to next call - executes the program until a call instruction is reached
If EIP is already on a call instruction, the entire call will be executed. After this call is returned execution will continue until another call is reached.

tc

tc
..

Trace to next call - executes the program until a call instruction is reached
If EIP is already on a call instruction, the debugger will trace into the call and continue executing until another call is reached.

pa

pa StopAddr


par
pa StopAddr "Command"
pa =StartAddress StopAddr ["Command"]

Step to address; StopAddr = address at which execution will stop
Called functions are treated as a single unit

Toggle display of registers and flags
Command = debugger command to be executed after the step is performed
StartAddress = Causes execution to begin at the specified address. Default is the current EIP.

ta

ta StopAddr
..

Trace to address; StopAddr = address at which execution will stop
Called functions are traced as well

wt

wt

wt [Options] [= StartAddr] [EndAddr]
wt -l Depth ..
wt -m Module [-m Module2] ..
wt -i Module [-i Module2] ..
wt -oa ..
wt -or ..
wt -oR ..
wt -nc ..
wt -ns ..
wt -nw ..

Trace and watch data. Go to the beginning of a function and do a wt. It will run through the entire function and display statistics.

StartAddr = execution begin; EndAddr = address at which to end tracing (default = after RET of current function)
l = maximum depth of traced calls
m = restrict tracing to Module
i = ignore code from Module
oa = dump actual address of call sites
or = dump return register values (EAX value) of sub-functions
oR = dump return register values (EAX value) in the appropriate type
nc = no info for individual calls
ns = no summary info
ns = no warnings

.step_filter

.step_filter
.step_filter "FilerList"
.step_filter /c

Dump current filter list = functions that are skipped when tracing (t, ta, tc)
FilterList = Filter 1; Filter 2; ... symbols associated with functions to be stepped over (skipped)
clear the filter list

.step_filter is not very useful in assembly mode, as each function call is on a different line.

ggo
g `:123`; ? poi(counter); gexecutes the current program to source line 123; print the value of counter; resume execution
psingle step
prtoggle displaying of registers
p 5 "kb"5x steps, execute "kb" thereafter
pcstep to next CALL instruction
pa 7c801b0bstep until 7c801b0b is reached
wttrace and watch sub-functions
wt -l 4 -oRtrace sub-functions to depth 4, display their return values
15) Call stack
Cmd Variants / Params Description

k

k [n] [f] [L] [#Frames]
kb ...
kp ...
kP ...
kv ...

dump stack; n = with frame #; f = distance between adjacent frames; L = omit source lines; number of stack frames to display
first 3 params
all params: param type + name + value
all params formatted (new line)
FPO info, calling convention

kd

kd [WordCnt]

display raw stack data + possible symbol info == dds esp

kM

DML variant with links to .frame #;dv

.kframes

Set stack length. The default is 20 (0x14).

.frame

.frame
.frame #
.frame /r [#]

show current frame
specify frame #
show register values

The .frame command specifies which local context (scope) will be used to interpret local variables, or displays the current local context.
When executing a near call, the processor pushes the value of the EIP register (which contains the offset of the instruction following the CALL instruction) onto the stack (for use later as a return-instruction pointer). This is the first step in building a frame. Each time a function call is made, another frame is created so that the called function can access arguments, create local variables, and provide a mechanism to return to calling function. The composition of the frame is dependant on the function calling convention.

!uniqstack

!uniqstack
!uniqstack [b|v|p] [n]
!uniqstack -?

show stacks for all threads
[b = first 3 params, v = FPO + calling convention, p = all params: param type + name + value], [n = with frame #]
brief help

!findstack

!findstack Symbol
!findstack Symbol [0|1|2]
!findstack -?

locate all stacks that contain Symbol or module
[0 = show only TID, 1 = TID + frames, 2 = entire thread stack]
brief help

k display call stack
kn call stack with frame numbers
kb display call stack with first 3 params
kb 5 display first 5 frames only

To get more than 3 Function Arguments from the stack
dd ChildEBP+8 (Parameters start at ChildEBP+8)
dd ChildEBP+8 (frame X) == dd ESP (frame X-1)

!uniqstack get all stacks of our process (one for each thread)
!findstack kernel32 2 display all stacks that contain "kernel32"
.frame show current frame
.frame 2 set frame 2 for the local context
.frame /r 0d display registers in frame 0
16) Registers
Cmd Variants / Params Description

r

r
r Reg1, Reg2
r Reg=Value

r Reg:Type











r Reg:[Num]Type


~Thread r [Reg:[Num]Type]

Dump all registers
Dump only specified registers (i.e.: r eax, edx)
Value to assign to the register (i.e.: r eax=5, edx=6)

Type = data format in which to display the register (i.e.: r eax:uw)
ib = Signed byte
ub = Unsigned byte
iw = Signed word (2b)
uw = Unsigned word (2b)
id = Signed dword (4b)
ud = Unsigned dword (4b)
iq = Signed qword (8b)
uq = Unsigned qword (8b)
f = 32-bit floating-point
d = 64-bit floating-point

Num = number of elements to display (i.e.: r eax:1uw)
Default is full register length, thus r eax:uw would display two values as EAX is a 32-bit register.

Thread = thread from which the registers are to be read (i.e.: ~1 r eax)

rM

rM Mask
rM Mask Reg1, Reg2
rM Mask Reg=Value
..

Dump register types specified by Mask
Dump only specified registers from current mask
Value to assign to the register

Flags for Mask
0x1 = basic integer registers
0x4 = floating-point registers == rF
0x8 = segment registers
0x10 = MMX registers
0x20 = Debug registers
0x40 = SSE XMM registers == rX

rF

rF
rF Reg1, Reg2
rF Reg=Value
..

Dump all floating-point registers == rM 0x4
Dump only specified floating-point registers
Value to assign to the register

rX

rX
rX Reg1, Reg2
rX Reg=Value
..

Dump all SSE XMM registers == rM 0x40
Dump only specified SSE XMM registers
Value to assign to the register

rm

rm
rm ?
rm Mask

Dump default register mask. This mask controls how registers are displayed by the "r".
Dump a list of possible Mask bits
Specify the mask to use when displaying the registers.

rm ? show possible bit mask
rm 1 enable integer registers only
r dump all integer registers
r eax, edx dump only eax and edx
r eax=5, edx=6 assign new values to eax and edx
r eax:1ub dump only the first byte from eax
rm 0x20 enable debug register mask
r dump debug registers
rF dump all floating point register
rM 0x4 dump all floating point register
rm 0x4; r dump all floating point registers
17) Information about variables
Cmd Variants / Params Description

dt

dt -h
dt [mod!]Name
dt [mod!]Name Field [Field]
dt [mod!]Name [Field] Addr
dt [mod!]Name*

dt [-n|y] [mod!]Name [-n|y] [Field] [Addr]


dt [-n|y] [mod!]Name [-n|y] [Field] [Addr] -abcehioprsv

Brief help
Dump variable info
Dump only 'field-name(s)' (struct or unions)
Addr of struct to be dumped
list symbols (wildcard)

-n Name = param is a name (use if name can be mistaken as an address)
-y Name = partially match instead of default exact match

-a = Shows array elements in new line with its index
-b = Dump only contiguous block of struct
-c = Compact output (all fields in one line)
-i = Does not indent the subtypes
-l ListField = Field which is pointer to the next element in list
-o = Omit the offset value (fields of struct)
-p = Dump from physical address
-r[l] = Recursively dump subtypes/fields (up to l levels)
-s [size] = For enumeration only, enumerate types only of given size.
-v = Verbose output.

dv

dv
dv Pattern
dv [/i /t /V] [Pattern]
dv [/i /t /V /a /n /z] [Pattern]

display local variables and parameters
vars matching Pattern
i = type (local, global, parameter), t = data type, V = memory address or register location
a = sort by Addr, n = sort by name, z = sort by size

dt ntdll!_PEB* list all variables that contain the word _PEB
dt ntdll!_PEB* -v list with verbose output (address and size included)
dt ntdll!_PEB* -v -s 9 list only symbols whose size is 9 bytes
dt ntdll!_PEB dump _PEB info
dt ntdll!_PEB @$peb dump _PEB for our process
dt ntdll!_PEB 7efde000 dump _PEB at Addr 7efde000
You can get our process's PEB address with "r @$peb" or with "!peb".
dt ntdll!_PEB Ldr SessionId dump only PEB's Ldr and SessionId fields
dt ntdll!_PEB Ldr -y OS* dump Ldr field + all fields that start with OS*
dt mod!var m_cs. dump m_cs and expand its subfields
dt mod!var m_cs.. expand its subfields for 2 levels
dt ntdll!_PEB -r2 dump recursively (2 levels)
dv /t /i /V dump local variables with type information (/t), addresses and EBP offsets (/V), classify them into categories (/i)
Note: dv will also display the value of a THIS pointer for methods called with the "this calling-convention".
BUG: You must first execute a few commands before dv displays the correct value.
Right at a function's entry point the THIS pointer is present in ECX, so you can easily get it from there.
18) Memory
Cmd Variants / Params Description

d*

d[a| u| b| w| W| d| c| q| f| D] [/c #] [Addr]













dy[b | d] ..

Display memory [#columns to display]
a = ascii chars
u = Unicode chars

b = byte + ascii
w = word (2b)
W = word (2b) + ascii
d = dword (4b)
c = dword (4b) + ascii
q = qword (8b)

f = floating point (single precision - 4b)
D = floating point (double precision - 8b)

b = binary + byte
d = binary + dword

e*

e[ b | w | d | q | f | D ] Addr Value








e[ a | u | za | zu ] Addr "String"

Edit memory
b = byte
w = word (2b)
d = dword (4b)
q = qword (8b)

f = floating point (single precision - 4b)
D = floating point (double precision - 8b)

a = ascii string
za = ascii string (NULL-terminated)
u = Unicode string
zu = Unicode string (NULL-terminated)

ds, dS


ds [/c #] [Addr]
dS [/c #] [Addr]

Dump string struct (struct! not null-delimited char sequence)
s = STRING or ANSI_STRING
S = UNICODE_STRING

d*s


dds [/c #] [Addr]
dqs [/c #] [Addr]

Display words and symbols (memory at Addr is assumed to be a series of addresses in the symbol table)
dds = dwords (4b)
dqs = qwords (8b)

dd*, dq*, dp*




dd*
dq*
dp*


d*a
d*u
d*p

Display referenced memory = display pointer at specified Addr, dereference it, and then display the memory at the resulting location in a variety of formats.

the 2nd char determines the pointer size used:
dd* -> 32-bit pointer used
dq* -> 64-bit pointer used
dp* -> standard size: 32-bit or 64-bit, depending on the CPU architecture

the 3rd char determines how the dereferenced memory is displayed:
d*a -> dereferenced mem as asci chars
d*u -> dereferenced mem as Unicode chars
d*p -> dereferenced mem as dword or qword, depending on the CPU architecture. If this value matches any known symbol, this symbol is displayed as well.

dl




dl[b] Addr MaxCount Size

Display linked list (LIST_ENTRY or SINGLE_LIST_ENTRY)
b = dump in reverse order (follow BLinks instead of FLinks)
Addr = start address of the list
MaxCount = max # elements to dump
Size = Size of each element

Use !list to execute some command for each element in the list.

!address


!address -?
!address Addr
!address -summary
!address -RegionUsageXXX

Display info about the memory used by the target process
Brief help
Dump info for region with Addr
Dump summary info for process
Dump specified regions (RegionUsageStack, RegionUsagePageHeap, ..)

!vprot

!vprot -?
!vprot Addr

Brief Help
Dump virtual memory protection info

!mapped_file

!mapped_file -?
!mapped_file Addr

Brief Help
Dump name of the file containing given Addr

dd 0046c6b0 display dwords at 0046c6b0
dd 0046c6b0 L1 display 1 dword at 0046c6b0
dd 0046c6b0 L3 display 3 dwords at 0046c6b0
du 0046c6b0 display Unicode chars at 0046c6b0
du 0046c6b0 L5 display 5 Unicode chars at 0046c6b0
dds esp == kd display words and symbols on stack
!mapped_file 00400000 Dump name of file containing address 00400000
!address show all memory regions of our process
!address -RegionUsageStack show all stack regions of our process
!address esp show info for committed sub-region for our thread's stack.
Note: For stack overflows SubRegionSize (size of committed memory) will be large, i.e.:
   AllocBase : SubRegionBase - SubRegionSize
   ---------------------------------------------
   001e0000 : 002d6000 - 0000a000



Determine stack usage for a thread
		
                Stack Identifier           Memory Identifier ^
                ---------------------------------------------------------
--------------  <- _TEB.StackBase          SubRegionBase3 + SubRegionSize3



|            |
| MEM_COMMIT |
|            |
|------------|  <- _TEB.StackLimit         SubRegionBase3 ^, SubRegionBase2 + SubRegionSize2
| PAGE_GUARD |
|------------|                             SubRegionBase2 ^, SubRegionBase1 + SubRegionSize1 
|            |
|MEM_RESERVED|
|            |
|------------|  <- _TEB.DeallocationStack  AllocationBase or RegionBase, SubRegionBase1 ^
  
                DeallocationStack: dt ntdll!_TEB TebAddr DeallocationStack
				
From MSDN CreateThread > dwStackSize > "Thread Stack Size":
"Each new thread receives its own stack space, consisting of both committed and reserved memory. By default, each thread uses 1 Mb of reserved memory, and one page of committed memory. The system will commit one page block from the reserved stack memory as needed."
19) Manipulating memory ranges
Cmd Variants / Params Description

c

c Range DestAddr

Compare memory

m

m Range DestAddr

Move memory

f

f Range Pattern

Fill memory. Pattern = a series of bytes (numeric or ASCII chars)

s

s Range Pattern

s -[Flags]b Range Pattern


s -[Flags]w Range 'Pattern'
s -[Flags]d Range 'Pattern'
s -[Flags]q Range 'Pattern'


s -[Flags]a Range "Pattern"
s -[Flags]u Range "Pattern"


s -[Flags,l length]sa Range
s -[Flags,l length]su Range


s -[Flags]v Range Object

Search memory

b = byte (default value)
Pattern = a series of bytes (numeric or ASCII chars)

w = word (2b)
d = dword (4b)
q = qword (8b)
Pattern = enclosed in single quotation marks (for example, 'Tag7')

a = ascii string (must not be null-terminated)
u = Unicode string (must not be null-terminated)
Pattern = enclosed in double quotation marks (for example, "This string")

Search for any memory containing printable ascii strings
Search for any memory containing printable Unicode strings
Length = minimum length of such strings; the default is 3 chars

Search for objects of the same type.
Object = Addr of a pointer to the Object or of the Object itself

Flags
-------
w = search only writable memory
1 = output only addresses of search matches (useful if you are using the .foreach)
Flags must be surrounded by a single set of brackets without spaces.
Example: s -[swl 10]Type Range Pattern

.holdmem


.holdmem -a Range
.holdmem -o
.holdmem -c Range
.holdmem -D
.holdmem -d { Range | Address }

Hold and compare memory. The comparison is made byte-for-byte
Memory range to safe
Display all saved memory ranges
Compares Range to all saved memory ranges
Delete all saved memory ranges
Delete specified memory ranges (any saved range containing Addr or overlapping with Range)

c Addr (Addr+100) DestAddr compare 100 bytes at Addr with DestAddr
c Addr L100 DestAddr -||-
m Addr L20 DestAddr move 20 bytes from Addr to DestAddr
f Addr L20 'A' 'B' 'C' fill specified memory location with the pattern "ABC", repeated several times
f Addr L20 41 42 43 -||-
s 0012ff40 L20 'H' 'e' 'l' 'l' 'o' search memory locations 0012FF40 through 0012FF5F for the pattern "Hello"
s 0012ff40 L20 48 65 6c 6c 6f -||-
s -a 0012ff40 L20 "Hello" -||-
s -[w]a 0012ff40 L20 "Hello" search only writable memory
20) Memory: Heap
Cmd Variants / Params Description

!heap

!heap -?

!heap
!heap -h
!heap -h [HeapAddr | Idx | 0]
!heap -v [HeapAddr | Idx | 0]
!heap -s [HeapAddr | 0]
!heap -i [HeapAddr]
!heap -x [-v] Address
!heap -l

Brief help

List heaps with index and HeapAddr
List heaps with index and range (= startAddr(=HeapAddr), endAddr)
Detailed heap info [Idx = heap Idx, 0 = all heaps]
Validate heap [Idx = heap Idx, 0 = all heaps]
Summary info, i.e. reserved and committed memory [Idx = heap Idx, 0 = all heaps]
Detailed info for a block at given address
Search heap block containing the address (v = search the whole process virtual space)
Search for potentially leaked heap blocks

!heap -b, -B

!heap Heap -b [alloc | realloc | free] [Tag]
!heap Heap -B [alloc | realloc | free]

Set conditional breakpoint in the heap manager [Heap = HeapAddr | Idx | 0]
Remove a conditional breakpoint

!heap -flt

!heap -flt s Size
!heap -flt r SizeMin SizeMax

Dump info for allocations matching the specified size
Filter by range

!heap -stat

!heap -stat
!heap -stat -h [HeapHandle | 0]

Dump heap handle list
Dump usage statistic for every AllocSize [HeapHandle = given heap | 0 = all heaps].
The statistic includes AllocSize, #blocks, TotalMem for each AllocSize.

!heap -p

!heap -p -?
!heap -p
!heap -p -h HeapHandle
!heap -p -a UserAddr
!heap -p -all

Extended page heap help
Summary for NtGlobalFlag, HeapHandle + NormalHeap list **
Detailed info about a page heap with Handle
Details of heap allocation containing UserAddr. Prints backtraces when available.
Details of all allocations in all heaps in the process.
The output includes UserAddr and AllocSize for every HeapAlloc call.

It seems that the following applies for windows XP SP2:

a) Normal heap

  1. CreateHeap -> creates a _HEAP
  2. AllocHeap -> creates a _HEAP_ENTRY
b) Page heap enabled (gflags.exe /i +hpa)
  1. CreateHeap -> creates a _DPH_HEAP_ROOT (+ _HEAP + 2x _HEAP_ENTRY)**
  2. AllocHeap -> creates a _DPH_HEAP_BLOCK
** With page heap enabled there will still be a _HEAP with two constant _HEAP_ENTRY's for every CreateHeap call.



Term Description Heap type
HeapHandle = value returned by HeapCreate or GetProcessHeap
For normal heap: HeapHandle == HeapStartAddr
Normal & page
HeapAddr = startAddr = NormalHeap Normal & page
UserAddr, UserPtr = value in the range [HeapAlloc...HeapAlloc+AllocSize]
For normal heap this range is further within Heap[startAddr-endAddr]
Normal & page
UserSize = AllocSize (value passed to HeapAlloc) Normal & page
_HEAP = HeapHandle = HeapStartAddr
For every HeapCreate a _HEAP struct is created.
You can use "!heap -p -all" to get these addresses.
Normal heap
_HEAP_ENTRY For every HeapAlloc a _HEAP_ENTRY is created.
You can use "!heap -p -all" to get these addresses.
Normal heap
_DPH_HEAP_ROOT = usually HeapHandle + 0x1000
For every HeapCreate a _DPH_HEAP_ROOT is created.
You can use "!heap -p -all" to get these addresses.
Page heap
_DPH_HEAP_BLOCK For every HeapAlloc a _DPH_HEAP_BLOCK is created.
You can use "!heap -p -all" to get these addresses.
Page heap

dt ntdll!_HEAP dump _HEAP struct
dt ntdll!_DPH_HEAP_ROOT dump _DPH_HEAP_ROOT struct.
Enable page heap. Then you can use "!heap -p -all" to get addresses of actual _DPH_HEAP_ROOT structs in your process.
dt ntdll!_DPH_HEAP_BLOCK dump _DPH_HEAP_BLOCK struct.
Enable page heap. Then you can use "!heap -p -all" to get addresses of actual _DPH_HEAP_BLOCK structs in your process.
!heap list all heaps with index and HeapAddr
!heap -h list all heaps with range information (startAddr, endAddr)
!heap -h 1 detailed heap info for heap with index 1
!heap -s 0 Summary for all heaps (reserved and committed memory, ..)
!heap -flt s 20 Dump heap allocations of size 20 bytes
!heap -stat Dump HeapHandle list. HeapHandle = value returned by HeapCreate or GetProcessHeap
!heap -stat -h 00150000 Dump usage statistic for HeapHandle = 00150000
!heap 2 -b alloc mtag Breakpoint on HeapAlloc calls with TAG=mtag in heap with index 2
!heap -p Dump heap handle list
!heap -p -a 014c6fb0 Details of heap allocation containing address 014c6fb0 + call-stack if available
!heap -p -all Dump details of all allocations in all heaps in the process


Who allocated memory - who called HeapAlloc?
  1. Select "Create user mode stack trace database" for your image in GFlags (gflags.exe /i +ust)
  2. From WinDbg's command line do a !heap -p -a , where is the address of your allocation ***.
  3. While !heap -p -a will dump a call-stack, no source information will be included.
  4. To get source information you must additionally enable page heap in step 1 (gflags.exe /i +ust +hpa)
  5. Do a dt ntdll!_DPH_HEAP_BLOCK StackTrace , where is the DPH_HEAP_BLOCK address retrieved in step 3.
  6. Do a dds ", where is the value retrieved in step 5.
    Note that dds will dump the stack with source information included.


Who created a heap - who called HeapCreate?
  1. Select "Create user mode stack trace database" and "Enable page heap" for your image in GFlags (gflags.exe /i +ust +hpa)
  2. a) From WinDbg's command line do a !heap -p -h , where is the value returned by HeapCreate. You can do a !heap -stat or !heap -p to get all heap handles of your process.
    b) Alternatively you can use !heap -p -all to get addresses of all _DPH_HEAP_ROOT's of your process directly.
  3. Do a dt ntdll!_DPH_HEAP_ROOT CreateStackTrace , where is the address of a _DPH_HEAP_ROOT retrieved in step 2
  4. Do a dds , where is the value retrieved in step 3.


Finding memory leaks
  • From WinDbg's command line do a !address –summary.
    If RegionUsageHeap or RegionUsagePageHeap are growing, then you might have a memory leak on the heap. Proceed with the following steps.
  1. Enable "Create user mode stack trace database" for your image in GFlags (gflags.exe /i +ust)
  2. From WinDbg's command line do a !heap -stat, to get all active heap blocks and their handles.
  3. Do a !heap -stat -h 0. This will list down handle specific allocation statistics for every AllocSize.
    For every AllocSize the following is listed: AllocSize, #blocks, and TotalMem. Take the AllocSize with maximum TotalMem.
  4. Do a !heap -flt s . =AllocSize that we determined in the previous step. This command will list down all blocks with that particular size.
  5. Do a !heap -p -a to get the stack trace from where you have allocated that much bytes. Use the that you got in step 4.
  6. To get source information you must additionally enable page heap in step 1 (gflags.exe /i +ust +hpa)
  7. Do a dt ntdll!_DPH_HEAP_BLOCK StackTrace , where is the DPH_HEAP_BLOCK address retrieved in step 5.
  8. Do a dds ", where is the value retrieved in step 7.
    Note that dds will dump the stack with source information included.


*** What is a ?
  1. is usually the address returned by HeapAlloc:
    int AllocSyze = 0x100000; 	// == 1 MB
    BYTE* pUserAddr = (BYTE*) HeapAlloc( GetProcessHeap(), HEAP_ZERO_MEMORY, AllocSyze); 
  2. Often any address in the range [UserAddr....UserAddr+AlloSize] is also a valid parameter:
    !heap -p -a [UserAddr....UserAddr+AlloSize]
21) Application Verifier
Application Verifier profiles and tracks Microsoft Win32 APIs (heap, handles, locks, threads, DLL load/unload, and more), Exceptions, Kernel objects, Registry, File system. With the !avrf extension we get access to this tracking information!
Cmd Variants / Params Description

!avrf

Displays Application Verifier options. If an Application Verifier Stop has occurred, reveal the nature of the stop and what caused it.

!avrf

-?

-vs N
-vs -a ADDR

-hp N
-hp -a ADDR

-cs N
-cs -a ADDR

-dlls N
-ex N
-cnt
-threads
-trm
-trace INDEX
-brk [INDEX]

Brief help

Dump last N entries from vspace log (MapViewOfFile, UnmapViewOfFile, ..).
Searches ADDR in the vspace log.

HeapAlloc, HeapFree, new, and delete log
Searches ADDR in the heap log.

DeleteCriticalSection API log (last #Entries). ~CCriticalSection calls this implicitly.
Searches ADDR in the critical section delete log.

LoadLibrary/FreeLibrary log
exception log
global counters (WaitForSingleObject, HeapAllocation calls, ...)
thread information + start parameters for child threads
TerminateThread API log
dump stack trace with INDEX.
dump or set/reset break triggers.

22) Logging extension (logexts.dll)

You must enable the following options for you image in GFlags:
-> "Create user mode stack trace database"
-> "Stack Backtrace: (Megs)" -> 10
-> It seems that you sometimes also need to check and specify the "Debugger" field in GFlags
Cmd Variants / Params Description

!logexts.help

displays all Logexts.dll extension commands

!loge

!loge [dir]

Enable logging + possibly initialize it if not yet done. Output directory optional.

!logi

Initialize (=inject Logger into the target application) but don't enable logging.

!logd

Disable logging

!logo

!logo
!logo [e|d] [d|t|v]

List output settings
Enable/disable [d - Debugger, t - Text file, v - Verbose log] output. Use logviewer.exe to examine Verbose logs.

!logc

!logc
!logc p #
!logc [e|d] *
!logc [e|d] # [#] [#]

List all categories
List APIs in category #
Enable/disable all categories
Enable/disable category #

!logb

!logb p
!logb f

Print buffer contents to debugger
Flush buffer to log files

!logm

!logm
!logm [i|x] [DLL] [DLL]

Display module inclusion/exclusion list
Specify module inclusion/exclusion list



Enable 19-ProcessesAndThreads and 22-StringManipulation logging:
!logeEnable logging
!logc d *Disable all categories
!logc p 19Display APIs of category 19
logc e 19 22Enable category 19 and 22
!logo d vDisable verbose output
!logo d tDisable text output
!logo e dEnable debugger output
Between 1 November 2007 and 31 Januar 2009 this article was published on software.rkuster.com where it was viewed 28.705 times.
 
Comments (6) Add Comment Expand all Comments RSS Feed
windbg question kam 19 Feb 2010 - 21:36     
Re: windbg question from kam Robert Kuster 18 Feb 2010 - 18:02     
windbg question kam 12 Feb 2010 - 18:28     
Re: Pattern matching Robert Kuster 14 May 2009 - 03:05     
Pattern matching adrian hodos 12 May 2009 - 18:17     
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