perf: sort-pmuevents: really keep array terminators

Commit e1382583cd50 ("perf: sort-pmuevents: don't drop elements") tried
to fix a case where the array terminator elements were dropped from the
sorted list breaking the build, but it only worked for the case where
the terminator is the only element of the array. When the array has other
elements the terminator will still be silently dropped, causing invalid
memory accesses at runtime when the perf utility iterates over the array.

Fix this by treating any unmatched entry as an array terminator and also
add a comment to make it a little more clear how things are ending up at
the right position in the sorted list.

(From OE-Core rev: 69c35a48c5100b884f1b633142b07222b9390e92)

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-kernel/perf/perf/sort-pmuevents.py

@@ -62,7 +62,10 @@ for struct in re.findall( struct_block_regex, data ):
             #print( "    name found: %s" % name.group(1) )
             entry_dict[struct[2]]['fields'][name.group(1)] = entry
 
-        if not entry_dict[struct[2]]['fields']:
+        # unmatched entries are most likely array terminators and
+        # should end up as the last element in the sorted list, which
+        # is achieved by using '0' as the key
+        if not cpuid and not name:
             entry_dict[struct[2]]['fields']['0'] = entry
 
 # created ordered dictionaries from the captured values. These are ordered by