[PATCH v2 2/4] tools/lib/perf: Add perf_record_header_attr_id()

[Namhyung Kim]

The HEADER_ATTR record has an event attr followed by the id array.  But
perf data from a different version could have different size of attr.

So it cannot just use event->attr.id to access the array.  Let's add the
perf_record_header_attr_id() macro to calculate the start of the array.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/lib/perf/include/perf/event.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
index ba2dcf64f4e6..e563dd8c3628 100644
--- a/tools/lib/perf/include/perf/event.h
+++ b/tools/lib/perf/include/perf/event.h
@@ -151,6 +151,10 @@ struct perf_record_header_attr {
 	__u64			 id[];
 };
 
+/* Returns the pointer to id array based on the actual attr size. */
+#define perf_record_header_attr_id(evt)			\
+	((void *)&(evt)->attr.attr + (evt)->attr.attr.size)
+
 enum {
 	PERF_CPU_MAP__CPUS = 0,
 	PERF_CPU_MAP__MASK = 1,
-- 
2.42.0.rc1.204.g551eb34607-goog