so I'm trying to track down a weird bug where opening a massive amount of
events (10000) in one group and then trying to read the values causes
memory corruption.
But in any case I ran across this code in kernel/events/core.c
+static void perf_event__read_size(struct perf_event *event)
+{
+ int entry = sizeof(u64); /* value */
+ int size = 0;
+ int nr = 1;
+
+ if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
+ size += sizeof(u64);
+
+ if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
+ size += sizeof(u64);
+
+ if (event->attr.read_format & PERF_FORMAT_ID)
+ entry += sizeof(u64);
^^^^^
+
+ if (event->attr.read_format & PERF_FORMAT_GROUP) {
+ nr += event->group_leader->nr_siblings;
+ size += sizeof(u64);
+ }
+
+ size += entry * nr;
+ event->read_size = size;
+}
Shouldn't that be
if (event->attr.read_format & PERF_FORMAT_ID)
size += sizeof(u64);
otherwise we are allocating 16-bytes for each entry rather than 8-bytes
if PERF_FORMAT_ID is specified? or am I missing something?
I tried to track down where this change originated but my git powers are
not enough to get a git blame to work past a file rename.
Vince
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