we want to export, so that userspace can deal with sane
name/value pairs.
+ Userspace must be prepared for the possibility that attributes
+ define overlapping bit ranges. For example:
+ attr1 = 'config:0-23'
+ attr2 = 'config:0-7'
+ attr3 = 'config:12-35'
+
Example: 'config1:1,6-10,44'
Defines contents of attribute that occupies bits 1,6-10,44 of
perf_event_attr::config1.