Archive for July 14th, 2010

Notepad Debugging :-)

Wednesday, July 14th, 2010

Have you heard about the new method of visual notepad debugging? You don’t even need a debugger, just a notepad. If not, here’s a recipe:

1. Open a buggy application executable file or a DLL file you suspect in notepad.exe


2. Change the font to Webdings 

3. Search for a bang: ‘!’ (a bug in Webdings font)

4. Remove the bug and repeat the search

5. Remove that bug too

6. Find another bug and remove it too

7. You might consider “Replace All” if there are too many bugs in your application

8. Save the debugged file

9. Run it - if it crashes do a postmortem analysis - may be you overfixed your bugs. Or you might see a transmutation, in my case the 32-bit Win32 Application2Debug.exe became an MS-DOS application silently terminating after the launch: 

0:000> kL
ChildEBP RetAddr 
011ef874 76e45500 ntdll!KiFastSystemCallRet
011ef878 76e1b518 ntdll!ZwTerminateProcess+0xc
011ef888 76be41ec ntdll!RtlExitUserProcess+0x7a
011ef89c 0e75c85f kernel32!ExitProcess+0x12
011ef8a4 0e79b07f ntvdm!host_terminate+0x23
011ef8b0 0e781db6 ntvdm!terminate+0x78
011efbfc 0e78094b ntvdm!cmdGetNextCmd+0x294
011efc04 0e769d94 ntvdm!CmdDispatch+0xf
011efc10 0e771882 ntvdm!MS_bop_4+0x2f
011efc14 0e77278a ntvdm!EventVdmBop+0x29
011efc2c 0e73510b ntvdm!cpu_simulate+0x17a
011efc38 0e735086 ntvdm!host_main+0x5f
011efc74 0e7352bd ntvdm!main+0x3a
011efd54 76bed0e9 ntvdm!host_main+0x211
011efd60 76e219bb kernel32!BaseThreadInitThunk+0xe
011efda0 76e2198e ntdll!__RtlUserThreadStart+0x23
011efdb8 00000000 ntdll!_RtlUserThreadStart+0x1b

- Dmitry Vostokov @ + -

Crash Dump Analysis Patterns (Part 53b)

Wednesday, July 14th, 2010

This is a specialization of Blocked Thread pattern where a thread is waiting for a hardware I/O response. For example, a frozen system initialization thread is waiting for a response from one of ACPI general register ports:

kd> kL 100
ChildEBP RetAddr 
f7a010bc f74c5a57 hal!READ_PORT_UCHAR+0×7
f7a010c8 f74c5ba4 ACPI!DefReadAcpiRegister+0xa1
f7a010d8 f74b4d78 ACPI!ACPIReadGpeStatusRegister+0×10
f7a010e4 f74b6334 ACPI!ACPIGpeIsEvent+0×14
f7a01100 8054157d ACPI!ACPIInterruptServiceRoutine+0×16
f7a01100 806d687d nt!KiInterruptDispatch+0×3d
f7a01194 804f9487 hal!HalEnableSystemInterrupt+0×79
f7a011d8 8056aac4 nt!KeConnectInterrupt+0×95
f7a011fc f74c987c nt!IoConnectInterrupt+0xf2
f7a0123c f74d13f0 ACPI!OSInterruptVector+0×76
f7a01250 f74b5781 ACPI!ACPIInitialize+0×154
f7a01284 f74cf824 ACPI!ACPIInitStartACPI+0×71
f7a012b0 f74b1e12 ACPI!ACPIRootIrpStartDevice+0xc0
f7a012e0 804ee129 ACPI!ACPIDispatchIrp+0×15a
f7a012f0 8058803b nt!IopfCallDriver+0×31
f7a0131c 805880b9 nt!IopSynchronousCall+0xb7
f7a01360 804f515c nt!IopStartDevice+0×4d
f7a0137c 80587769 nt!PipProcessStartPhase1+0×4e
f7a015d4 804f5823 nt!PipProcessDevNodeTree+0×1db
f7a01618 804f5ab3 nt!PipDeviceActionWorker+0xa3
f7a01630 8068afc6 nt!PipRequestDeviceAction+0×107
f7a01694 80687e48 nt!IopInitializeBootDrivers+0×376
f7a0183c 806862dd nt!IoInitSystem+0×712
f7a01dac 805c61e0 nt!Phase1Initialization+0×9b5
f7a01ddc 80541e02 nt!PspSystemThreadStartup+0×34
00000000 00000000 nt!KiThreadStartup+0×16

kd> r
eax=00000000 ebx=00000000 ecx=00000002 edx=0000100c esi=00000000 edi=867d8008
eip=806d664b esp=f7a010c0 ebp=f7a010c8 iopl=1         nv up ei pl zr na pe nc
cs=0008  ss=0010  ds=0023  es=0023  fs=0030  gs=0000             efl=00001246
806d664b c20400          ret     4

kd> ub eip
806d663f cc              int     3
806d6640 cc              int     3
806d6641 cc              int     3
806d6642 cc              int     3
806d6643 cc              int     3
806d6644 33c0            xor     eax,eax
806d6646 8b542404        mov     edx,dword ptr [esp+4]
806d664a ec              in      al,dx

kd> version
System Uptime: 0 days 0:03:42.140

kd> !thread
THREAD 867c63e8  Cid 0004.0008  Teb: 00000000 Win32Thread: 00000000 RUNNING on processor 0
IRP List:
    867df008: (0006,0190) Flags: 00000000  Mdl: 00000000
Not impersonating
DeviceMap                 e1005460
Owning Process            0       Image:         <Unknown>
Attached Process          867c6660       Image:         System
Wait Start TickCount      39             Ticks: 1839 (0:00:00:18.416)
Context Switch Count      4            
UserTime                  00:00:00.000
KernelTime                00:00:00.911
Start Address nt!Phase1Initialization (0x80685928)
Stack Init f7a02000 Current f7a014a4 Base f7a02000 Limit f79ff000 Call 0
Priority 31 BasePriority 8 PriorityDecrement 0 DecrementCount 0

- Dmitry Vostokov @ + -