Find which HT-cores are sharing a physical core from /proc/cpuinfo

The ones that share the same physical core should have the same core id and physical id, with different processor number. Try this:

cat /proc/cpuinfo |egrep "processor|physical id|core id" | sed 's/^processor/\nprocessor/g'

The problem is already solved by Portable Hardware Locality (hwloc).

This utility will show how system is organized in terms of sharing physical packages, caches, physical cores. It supports HT and Linux too.