perf machine: Add a mechanism to inject stack frames

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.

Reviewed-by: James Clark <[e-mail]>
Signed-off-by: Alexandre Truong <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: John Garry <[e-mail]>
Cc: Leo Yan <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Mathieu Poirier <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: German Gomez <[e-mail]>
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/machine.c

···
 	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,
···
 	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;
···
 			if (err)
 				return (err < 0) ? err : 0;
 			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,