[Question] Possible XOR a Singly Linked List?

[x BlueRobot]

I was debugging (will post the example later) a dump file, which seemed to have a problem with a singly linked list and memory alignment leading to a access violation exception.

I noticed within one of the instructions, that a xor assembly instruction was used, I read that you could XOR through a linked list, but this seemed to only apply to a doubly linked list, therefore my question is, is it possible to xor on a singly linked list or that instruction completely unrelated to the problem with the singly linked list?

BSOD 0x0000001E, 1D, 3B on Computer Shutdown - Windows 7 Help Forums

 

[jcgriff2]

I am banned (as are most others here!!) from that site & therefore cannot download the zipped dump file(s).

Can you attach them here, please?

Thanks,

John

 

[x BlueRobot]

I'm uploading the files now :)

 

[x BlueRobot]

FOLLOWUP_IP: 
dxgmms1!VidSchDdiNotifyDpcWorker+36
fffff880`0fd40caa 33f6            [COLOR=#ff0000]xor[/COLOR]     esi,esi

This is the specific area I'm talking about.

 

[jcgriff2]

Sorry. . . don't know about xor.

All dumps named NVIDIA -

nvlddmkm.sys     Wed Oct 23 02:21:50 2013 (52676AFE)

Did you advise removal of Daemon Tools? -- just a suggestion

 

[x BlueRobot]

I advised they check they had the latest WHQL driver installed for nVidia, and then remove Daemon Tools.

 

[Vir Gnarus]

The XOR in this case is a common used assembly shortcut for zeroing a register, as it will zero any similarities between source and destination. Most CPU architectures perform this faster than pushing a zero value onto the register. You will see this kind of behavior in a lot of functions.

I'm pretty sure this has no application to the actual function of walking through a linked list. Rather, it is just a simple register cleaning operation. It may be involved in a related linked list function, but it in itself does not perform much outside of cleaning up a register for use.

Btw, concerning XOR on linked lists, yes, a XOR linked list is double. However, I'm personally not aware of how to do XOR lists at all if it's through a Windows API call. I'm pretty sure those require actual addresses and nor XOR differences. Correct me if I'm wrong.