enhance makedumpfile to dump process list from vmcore

[Prasad Koya]

Hi

We use makedumpfile to read the dmesg buffer from the vmcore. We are
working on adding a feature to makedumpfile to extract the "process
list" from /proc/vmcore. Our main use case is to save the processes
that were running at the time of kernel crash to a file on the
permanent storage from the kdump kernel. We intend to read a handful
of useful data for each running task: pid, parent pid, real parent
pid, priority, nice value, RSS, VM size, command, utime, stime, OOM
score.

Process list from vmcore can probably be read using crash utility, but
in our embedded system using makedumpfile to do that job makes sense
for us.

If such an option is useful for the general users of makedumpfile,
we'd like to get more inputs and contribute to this feature.

Thank you
Prasad