Question

Windbg u command

Asked by: Jonesey007

Hi,
I have a mini dump and am trying to find out whats causing my BSOD
When i press 'u' i get unassembed code, if i press 'u' again the output changes and so on and so on
Can someone tell me what im doing, am i moving down some sort of stack?

Thanks

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Asked On
2009-09-07 at 07:21:14ID24712702
Topics

Assembly Programming Language

,

Debugging Software for Development

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Answers

 

by: t0t0Posted on 2009-09-07 at 12:40:31ID: 25276941

You're unassembling code.  Look at your pair of hex addresses, notice they get bigger everytime you press 'u'? That's because it's advancing further along in memory. The hex pairs are your memory address and offset address.

Normally, you start at ????.0100. On my machine it's 0F00.0100.

If you want debug to return to the start again, enter 'u 100'.

Check out debug's commands by entering just a question mark (?)....

Below: example output from debug. Notice how I return to the start by entering 'u 100'?

-u
0F00:0100 059888        ADD     AX,8898
0F00:0103 0E            PUSH    CS
0F00:0104 0498          ADD     AL,98
0F00:0106 41            INC     CX
0F00:0107 F3            REPZ
0F00:0108 A4            MOVSB
0F00:0109 883E0798      MOV     [9807],BH
0F00:010D C70619960000  MOV     WORD PTR [9619],0000
0F00:0113 5E            POP     SI
0F00:0114 EB80          JMP     0096
0F00:0116 803E259901    CMP     BYTE PTR [9925],01
0F00:011B 7534          JNZ     0151
0F00:011D 00EF          ADD     BH,CH
0F00:011F 0E            PUSH    CS
-u
0F00:0120 96            XCHG    SI,AX
0F00:0121 01750D        ADD     [DI+0D],SI
0F00:0124 803E269902    CMP     BYTE PTR [9926],02
0F00:0129 7506          JNZ     0131
0F00:012B BAE989        MOV     DX,89E9
0F00:012E E93106        JMP     0762
0F00:0131 A02599        MOV     AL,[9925]
0F00:0134 A21396        MOV     [9613],AL
0F00:0137 D0E0          SHL     AL,1
0F00:0139 D0E0          SHL     AL,1
0F00:013B A21E99        MOV     [991E],AL
0F00:013E A01496        MOV     AL,[9614]
-u 100
0F00:0100 059888        ADD     AX,8898
0F00:0103 0E            PUSH    CS
0F00:0104 0498          ADD     AL,98
0F00:0106 41            INC     CX
0F00:0107 F3            REPZ
0F00:0108 A4            MOVSB
0F00:0109 883E0798      MOV     [9807],BH
0F00:010D C70619960000  MOV     WORD PTR [9619],0000
0F00:0113 5E            POP     SI
0F00:0114 EB80          JMP     0096
0F00:0116 803E259901    CMP     BYTE PTR [9925],01
0F00:011B 7534          JNZ     0151
0F00:011D 00EF          ADD     BH,CH
0F00:011F 0E            PUSH    CS
-q

                                              
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by: roman2Posted on 2009-09-07 at 22:35:49ID: 25278887

Hello, Jonesey007,
there are commands "k", "kb" and etc in the windbg to view the stack of the current thread. It's important that only registers and stack trace are available in the minidump.

20120131-EE-VQP-002

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