MANAGED DEBUGGING with WINDBG. Setting a Breakpoint. Part 1
Hi all,
This post is a continuation of MANAGED DEBUGGING with WINDBG. Preparing the Environment.
SETTING A BREAKPOINT. Part 1
We can only set breakpoints when doing live debugging, but many of the commands explained here can be used when doing dump analysis, too.
· We find the method where we want to set the breakpoint:
If we don’t know the name of the module, class or method we need, we can do the following:
0:004> !DumpDomain
...
--------------------------------------
Domain 1: 00094bd8
LowFrequencyHeap: 00094bfc
HighFrequencyHeap: 00094c54
StubHeap: 00094cac
Stage: OPEN
SecurityDescriptor: 00095938
Name: WindowsApplication1.exe
Assembly: 000d9748 [C:\Windows\assembly\GAC_32\mscorlib\2.0.0.0__b77a5c561934e089\mscorlib.dll]
ClassLoader: 0008d348
SecurityDescriptor: 000d6568
Module Name
790c2000 C:\Windows\assembly\GAC_32\mscorlib\2.0.0.0__b77a5c561934e089\mscorlib.dll
007823dc C:\Windows\assembly\GAC_32\mscorlib\2.0.0.0__b77a5c561934e089\sortkey.nlp
00782050 C:\Windows\assembly\GAC_32\mscorlib\2.0.0.0__b77a5c561934e089\sorttbls.nlp
Assembly: 000e4ba0 [C:\ __MANAGED DEBUGGING\BuggyNETApp\bin\Debug\WindowsApplication1.exe]
ClassLoader: 0008d658
SecurityDescriptor: 000e4b18
Module Name
00762c3c C:\ __MANAGED DEBUGGING\BuggyNETApp\bin\Debug\WindowsApplication1.exe
...
0:004> !DumpAssembly 000e4ba0
Parent Domain: 00094bd8
Name: C:\ __MANAGED DEBUGGING\BuggyNETApp\bin\Debug\WindowsApplication1.exe
ClassLoader: 0008d658
SecurityDescriptor: 00843678
Module Name
00762c3c C:\ __MANAGED DEBUGGING\BuggyNETApp\bin\Debug\WindowsApplication1.exe
0:004> !DumpModule -mt 00762c3c
Name: C:\ __MANAGED DEBUGGING\BuggyNETApp\bin\Debug\WindowsApplication1.exe
Attributes: PEFile
Assembly: 000e4ba0
LoaderHeap: 00000000
TypeDefToMethodTableMap: 007600c0
TypeRefToMethodTableMap: 007600ec
MethodDefToDescMap: 0076024c
FieldDefToDescMap: 00760344
MemberRefToDescMap: 007603a0
FileReferencesMap: 007605bc
AssemblyReferencesMap: 007605c0
MetaData start address: 01123128 (10832 bytes)
Types defined in this module
MT TypeDef Name
------------------------------------------------------------------------------
00763dbc 0x02000002 WindowsApplication1.My.MyApplication
00765e74 0x02000003 WindowsApplication1.My.MyComputer
00765c48 0x02000004 WindowsApplication1.My.MyProject
007661f4 0x02000005 WindowsApplication1.My.MyProject+MyForms
00766330 0x02000006 WindowsApplication1.My.MyProject+MyWebServices
00765de0 0x02000007 WindowsApplication1.My.MyProject+ThreadSafeObjectProvider`1
00766e94 0x02000008 WindowsApplication1.Form1
Types referenced in this module
MT TypeRef Name
------------------------------------------------------------------------------
5e4e3d4c 0x01000001 Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase
79104368 0x01000002 System.Collections.ArrayList
...
0:004> !DumpMT -md 00766e94
EEClass: 00ed0a30
Module: 00762c3c
Name: WindowsApplication1.Form1
mdToken: 02000008 (C:\ __MANAGED DEBUGGING\BuggyNETApp\bin\Debug\WindowsApplication1.exe)
BaseSize: 0x158
ComponentSize: 0x0
Number of IFaces in IFaceMap: 15
Slots in VTable: 395
--------------------------------------
MethodDesc Table
Entry MethodDesc JIT Name
7b05e348 7b4a4668 PreJIT System.Windows.Forms.Form.ToString()
...
7b068b6c 7b4a4680 PreJIT System.Windows.Forms.Form.OnResizeEnd(System.EventArgs)
00851638 00766d68 JIT WindowsApplication1.Form1.get_Button1()
...
0076c2d8 00766d60 JIT WindowsApplication1.Form1.InitializeComponent()
0076c1b4 00766e08 NONE WindowsApplication1.Form1.CopyMem(IntPtr, IntPtr, Int64)
0076c2ec 00766db8 NONE WindowsApplication1.Form1.Button1_Click(System.Object, System.EventArgs)
...
Now, the method we choose can be jitted (.NET compiles IL to asm when we are going to use a method for the first time - Just In Time-)/pre-jitted, or not:
0:004> !DumpMD 00766d60
Method Name: WindowsApplication1.Form1.InitializeComponent()
Class: 00ed0a30
MethodTable: 00766e94
mdToken: 06000021
Module: 00762c3c
IsJitted: yes
m_CodeOrIL: 00850a08
0:004> !DumpMD 00766db8
Method Name: WindowsApplication1.Form1.Button1_Click(System.Object, System.EventArgs)
Class: 00ed0a30
MethodTable: 00766e94
mdToken: 0600002d
Module: 00762c3c
IsJitted: no
m_CodeOrIL: ffffffff
If we know the name of the method and in which module we can find it, we can get the method descriptor and jitted address directly like this:
0:004> !Name2EE WindowsApplication1!WindowsApplication1.Form1.InitializeComponent
...
0:004> !Name2EE WindowsApplication1 WindowsApplication1.Form1.InitializeComponent
Module: 00762c3c (WindowsApplication1.exe)
Token: 0x06000021
MethodDesc: 00766d60
Name: WindowsApplication1.Form1.InitializeComponent()
JITTED Code Address: 00850a08
0:004> !Name2EE WindowsApplication1 WindowsApplication1.Form1.Button1_Click
Module: 00762c3c (WindowsApplication1.exe)
Token: 0x0600002d
MethodDesc: 00766db8
Name: WindowsApplication1.Form1.Button1_Click(System.Object, System.EventArgs)
Not JITTED yet. Use !bpmd -md 00766db8 to break on run.
And if we know the name of the method but not the module, we can still get the method descriptor and jitted address like this:
0:004> !Name2EE * WindowsApplication1.Form1.InitializeComponent
Module: 790c2000 (mscorlib.dll)
--------------------------------------
...
--------------------------------------
Module: 00762c3c (WindowsApplication1.exe)
Token: 0x06000021
MethodDesc: 00766d60
Name: WindowsApplication1.Form1.InitializeComponent()
JITTED Code Address: 00850a08
--------------------------------------
...
Like a process, an Application Domain or AppDomain is both a container and a boundary. The .NET runtime uses an AppDomain as a container for code and data and to isolate code inside of a secure boundary.
An AppDomain belongs to only a single process, but single process can hold multiple AppDomains: typically a system domain (tracks all domains), a shared domain (contains code which is shared between all the other app domains), and at least one other app domain (the main app domain of the app).
In ASP.NET, w3wp.exe will hold system and shared domains, and also a default domain and one app domain per web application (virtual directory marked as application):
0:000> !dumpdomain
--------------------------------------
System Domain: 7a38bb38
...
--------------------------------------
Shared Domain: 7a38c110
…
--------------------------------------
Domain 1: 001a8d58
…
Name: DefaultDomain
…
--------------------------------------
Domain 2: 001caff8
…
Name: /LM/w3svc/1/ROOT/DebuggingWorkshop-1-128030638920977997
…
Next post: MANAGED DEBUGGING with WINDBG. Setting a Breakpoint. Part 2.
Index: MANAGED DEBUGGING with WINDBG. Introduction and Index.
Regards,
Alex (Alejandro Campos Magencio)