What is the mount adapter I need to mount a Vivitar 28mm 1:2 No.22 (made by Kino, aka Kiron) lens on my Canon 600D? Is it the T/T2 lens mount?
I used to mount this lens on my dad's Olympus OM-10.
No. (I should clarify that. I mean, "no, that's not the right adapter." The answer to the underlying question, "can I use an Olympus OM-mount lens on my Canon EF-mount camera," is clearly, "yes.")
The T-mount lens is a screw-mount type introduced by Tamron as a universal mount (to be used with adapters to fit the various camera brands), and is a sort of precursor to their later Adaptall/Adaptall2 mount system. These days, the T-mount system is used mostly as an interface between cameras and other optical systems, like telescopes, microscopes and binoculars (using only one of the two optics, of course).
You would need an OM to EF adapter, like the Photodiox model listed here. Luckily, the OM mount had one of the longest flange-to-film distances ever, so the adapter is just a simple bit of metal with no additional optics, and will still allow infinity focus. Whether the adapted lens will work on your camera depends on whether your camera allows lenses with no electronic linkage to speak of to work (it varies by model—check your manual).