perf intel-pt: Fix corrupt data after perf inject from

Commit 42bbabed09ce6208 ("perf tools: Add hw_idx in struct branch_stack")
changed the format of branch stacks in perf samples. When samples use
this new format, a flag must be set in the corresponding event.

Synthesized branch stacks generated from Intel PT were using the new
format, but not setting the event attribute, leading to consumers
seeing corrupt data. This patch fixes the issue by setting the event
attribute to indicate use of the new format.

Fixes: 42bbabed09ce6208 ("perf tools: Add hw_idx in struct branch_stack")
Signed-off-by: Al Grant <[email protected]>
Acked-by: Adrian Hunter <[email protected]>
Reviewed-by: Mathieu Poirier <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Leo Yan <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mike Leach <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Suzuki Poulouse <[email protected]>
Cc: [email protected]
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Leo Yan <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 8 insertions, 1 deletions

diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index 2a8d245351e7..0af4e81c46e2 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -3017,8 +3017,15 @@ static int intel_pt_synth_events(struct intel_pt *pt,
 
 	if (pt->synth_opts.callchain)
 		attr.sample_type |= PERF_SAMPLE_CALLCHAIN;
-	if (pt->synth_opts.last_branch)
+	if (pt->synth_opts.last_branch) {
 		attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;
+		/*
+		 * We don't use the hardware index, but the sample generation
+		 * code uses the new format branch_stack with this field,
+		 * so the event attributes must indicate that it's present.
+		 */
+		attr.branch_sample_type |= PERF_SAMPLE_BRANCH_HW_INDEX;
+	}
 
 	if (pt->synth_opts.instructions) {
 		attr.config = PERF_COUNT_HW_INSTRUCTIONS;