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Subject[PATCH v4 2/6] perf tools: add a mechanism to inject stack frames
Date
From: Alexandre Truong <alexandre.truong@arm.com>

Add a mechanism for platforms to inject stack frames for the leaf
frame caller if there is enough information to determine a frame
is missing from dwarf or other post processing mechanisms.

Signed-off-by: Alexandre Truong <alexandre.truong@arm.com>
Signed-off-by: German Gomez <german.gomez@arm.com>
---
tools/perf/util/machine.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index fb8496df8432..3eddad009f78 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -2710,6 +2710,12 @@ static int find_prev_cpumode(struct ip_callchain *chain, struct thread *thread,
return err;
}

+static u64 get_leaf_frame_caller(struct perf_sample *sample __maybe_unused,
+ struct thread *thread __maybe_unused, int usr_idx __maybe_unused)
+{
+ return 0;
+}
+
static int thread__resolve_callchain_sample(struct thread *thread,
struct callchain_cursor *cursor,
struct evsel *evsel,
@@ -2723,9 +2729,10 @@ static int thread__resolve_callchain_sample(struct thread *thread,
struct ip_callchain *chain = sample->callchain;
int chain_nr = 0;
u8 cpumode = PERF_RECORD_MISC_USER;
- int i, j, err, nr_entries;
+ int i, j, err, nr_entries, usr_idx;
int skip_idx = -1;
int first_call = 0;
+ u64 leaf_frame_caller;

if (chain)
chain_nr = chain->nr;
@@ -2850,6 +2857,34 @@ static int thread__resolve_callchain_sample(struct thread *thread,
continue;
}

+ /*
+ * PERF_CONTEXT_USER allows us to locate where the user stack ends.
+ * Depending on callchain_param.order and the position of PERF_CONTEXT_USER,
+ * the index will be different in order to add the missing frame
+ * at the right place.
+ */
+
+ usr_idx = callchain_param.order == ORDER_CALLEE ? j-2 : j-1;
+
+ if (usr_idx >= 0 && chain->ips[usr_idx] == PERF_CONTEXT_USER) {
+
+ leaf_frame_caller = get_leaf_frame_caller(sample, thread, usr_idx);
+
+ /*
+ * check if leaf_frame_Caller != ip to not add the same
+ * value twice.
+ */
+
+ if (leaf_frame_caller && leaf_frame_caller != ip) {
+
+ err = add_callchain_ip(thread, cursor, parent,
+ root_al, &cpumode, leaf_frame_caller,
+ false, NULL, NULL, 0);
+ if (err)
+ return (err < 0) ? err : 0;
+ }
+ }
+
err = add_callchain_ip(thread, cursor, parent,
root_al, &cpumode, ip,
false, NULL, NULL, 0);
--
2.25.1
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