When loading the vmcore in crash you may find something similar to the message below:
WARNING: yourvmcorefilename: may be truncated or incomplete
PT_LOAD p_offset: 3358304032
bytes required: 17048508192
dumpfile size: 5412478976
crash: read error: kernel virtual address: ffff81042ff0eac0 type: "cpu_pda entry"
crash: read error: kernel virtual address: ffff810230005458 type: "pglist node_id"
A workaround to get some data in this case is to use a recent crash and use the --minimal parameter.
crash --minimal vmcorefilehere vmlinux
NOTE: minimal mode commands: log, dis, rd, sym, eval and exit
This will present you with a limited set of commands that you can use that will allow you to get basic data from the vmcore.
It is important to note that backtraces are not entirely accurate and that when you inspect memory it may not be available. Crash usually throws an error when this is the case.
This is not an april fools joke.