For your review, this patch adds support for arch-dependent symbolic
event names to the "perf stat" tool, and could be expanded to other
"perf *" commands fairly easily, I suspect.
To support arch-dependent event names without adding arch-dependent code
to perf, I added a callout mechanism whereby perf will look for the
environment variable: PERF_ARCH_DEP_LIB, and if it exists, it will try
to open it as a shared object. If that succeeds, it looks for the symbol
"parse_arch_dep_event". If that exists, that function will be called by
parse_events() before all of the other event parsing functions in
parse-events.c. It is passed the same arguments as the other
parse_*_event functions, namely the event string and a pointer to an
event attribute structure.
As the code existed, "perf stat" would print out the count results, but
for raw events (which is how arch-dependent events are supported in
perf_events), it would just print out a raw code. This is not
acceptable, especially when a symbolic name was placed on the command
line. So I changed the code to save away the event name that was passed
on the command line, rather than doing a reverse translation to an event
string based on the event type and config fields of the attr structure.
In this way, there's no need for a reverse translation function in the
arch-dependent library; only a event string->attr struct function is
I could well be missing something, but I don't understand why reverse
translation is ever needed in perf, as long as the tool keeps track of
the original event strings.