vmss file is VMware virtual machine snapshot file and contains all the necessary memory dump that crash requires. 

there is public available parse to read the format. https://code.google.com/p/vmsnparser/ 

there is vmss2core (https://labs.vmware.com/flings/vmss2core) to convert it to standard core file. 

and this patch just enables crash to read it directly.

rgds,

Dyno