Command line tool to read CPU Model Specific Registers (MSR).
For example, to read the Time Stamp Counter (in a very inefficient manner), on CPU #0 (x86):
$ sudo ./readmsr.py 0 0x10 191f 1c7032c8
I'm using it to read the SMI (system management interrupt) counter on Nehalem and newer Intel CPUs:
$ sudo ./readmsr.py 0 0x34 0 310