Surface shader built-in input variables

I'm investigating how shaders work in Unity. It appears that there are a bunch of built-in variables that could be used as vertex shader inputs. The ones that I've found

• viewDir

• lightDir

• vlight

• uv_MainTex

• uv_BumpMap

• uv_EmissionMap

Viewing debug version of my surface shaders reveals that engine copies the values with matching names. The problem is that I can't find the full list of those variables - neither in documentation nor in include files. So where is it ?