Difference between revisions of "Windows BSOD"

Revision as of 12:30, 13 October 2023

Windows Crash Dumps

If you do managed to get a Blue Screen Of Death (BSOD), Windows should in theory write a crash dump file to:

C:\Windows\MEMORY.DMP

The dump file can be analyzed with WinDbg.exe

Debug builds of ZFSin include debugging symbols to assist in dump analysis which are located at:

C:\Program Files\OpenZFS On Windows\symbols\

WinDbg.exe at the Command Line

Once installed, WinDbg.exe can be run from a CMD.com or PowerShell terminal with Administrative privileges:

WinDbgX.exe -y ‘C:\Program Files\OpenZFS On Windows\symbols\’ -z C:\Windows\MEMORY.DMP

This will launch the application and you can perform dump analysis with:

kd> !analyze -v

To run the analysis in a single command:

WinDbgX.exe -y ‘C:\Program Files\OpenZFS On Windows\symbols\’ -z C:\Windows\MEMORY.DMP -c !analyze -v

WinDbg.exe in the GUI

Launch WinDbg.exe and set the symbol path:

kd> .symfix c:\cache
kd> .sympath+ C:\Program Files\OpenZFS On Windows\symbols
kd> .reload

So that it can load both the symbols from Microsoft, and from the installed Open ZFS directory.

Open the crash dump file with:

File: Open crash dump
C:\Windows\MEMORY.DMP

Perform the analysis:

kd> !analyze -v

Should at least show the stack.

• 

  Set symbol path

• 

  Add path

• 

  Load crash dump

• 

  Locate minidump

• 

  minidump loading

• 

  analyze with stack

Example Crash report

A successful crash dump would look something like:

 	ZFSin!zfs_range_lock_reader+0x290 [c:\src\zfsin\zfsin\zfs\module\zfs\zfs_rlock.c @ 417]	C/C++/ASM
	ZFSin!zfs_range_lock+0x16d [c:\src\zfsin\zfsin\zfs\module\zfs\zfs_rlock.c @ 453]	C/C++/ASM
	ZFSin!zil_lwb_commit+0x99f [c:\src\zfsin\zfsin\zfs\module\zfs\zil.c @ 1570]	C/C++/ASM
	ZFSin!zil_process_commit_list+0x30e [c:\src\zfsin\zfsin\zfs\module\zfs\zil.c @ 2182]	C/C++/ASM
	ZFSin!zil_commit_writer+0x111 [c:\src\zfsin\zfsin\zfs\module\zfs\zil.c @ 2318]	C/C++/ASM

If you get only ZFSin+0x"hex-number" it means it is not reading the debug symbols correctly, to be able to convert the hex-number into a function name.

Debug Print Buffer

Windows features a circular debug print buffer which can also be written to disk:

Old

kd> r $t0 = poi(ZFSin!cbuf)
kd> .writemem C:\Users\<your Windows username>\Desktop\cbuf.txt $t0 L100000

New

kd> r $t0 = poi(OpenZFS!cbuf)
kd> .writemem C:\Users\<your Windows username>\Desktop\cbuf.txt $t0 L100000

Do not worry if you get a message about short write, it just means you have not yet filled the buffer.

This will include -EB- at the end of the buffer. Do not worry if the rest of the buffer has "@" (nul) symbols, it just means the buffer was not yet full.

Please provide the contents of the dump analysis and cbuf.txt in you ZFSin in your crash-related tickets.