[PATCH v1 04/12] perf annotate-data: Count flexible array accesses for the whole struct

[Arnaldo Carvalho de Melo]

From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

The per-member percentage sums the histogram entries in the member's
own [offset, offset + size) range.  A flexible array member is resolved
past the end of its struct, so the struct row only covered its declared
size and showed 0.00% while the member row showed 100.00% and the
header said N samples.

Take a member's extent as the end of its last child as well, so the
struct counts what was resolved past it.  Union members all start at
offset 0, so a plain union keeps its size; a member that is itself a
struct with a flexible array extends the union too.

Extend tests/shell/data_type_flex_array.sh to check that the accesses
count for the struct in the percent, samples and period columns.

Fixes: aaca646915a1bb53 ("perf annotate-data: Adjust type offset for flex-array")
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 .../perf/tests/shell/data_type_flex_array.sh  | 40 ++++++++++++++++++-
 tools/perf/util/annotate-data.c               | 24 ++++++++++-
 2 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/tools/perf/tests/shell/data_type_flex_array.sh b/tools/perf/tests/shell/data_type_flex_array.sh
index 983cde2b3c7d2b29..7a7a782320afee23 100755
--- a/tools/perf/tests/shell/data_type_flex_array.sh
+++ b/tools/perf/tests/shell/data_type_flex_array.sh
@@ -100,5 +100,43 @@ if ! grep -Fq "# data-type: struct flex +0x4 (data)" "$perfout"; then
 	exit 1
 fi
 
-echo "flexible array member resolved"
+# The accesses to the flexible array are resolved past the end of the
+# struct: they must count for the struct, not only for the member.
+if ! perf annotate --data-type -i "$perfdata" --stdio > "$perfout" 2>/dev/null; then
+	echo "FAIL: perf annotate --data-type"
+	cleanup
+	exit 1
+fi
+
+if ! awk '
+	$1 + 0 == 100.00 && /struct flex/ { struct_ok = 1 }
+	$1 + 0 == 100.00 && /char\[\]/ && /data;/ { data_ok = 1 }
+	$1 + 0 == 0.00 && /int/ && /len;/ { len_ok = 1 }
+	END { exit !(struct_ok && data_ok && len_ok) }
+' <(sed -n "/^Annotate type: 'struct flex' in/,/^Annotate type: /p" "$perfout"); then
+	echo "FAIL: --data-type does not count the flexible array accesses"
+	cleanup
+	exit 1
+fi
+
+# Same with the samples and period columns, the other two display modes.
+for mode in --show-nr-samples --show-total-period; do
+	if ! perf annotate --data-type -i "$perfdata" --stdio "$mode" > "$perfout" 2>/dev/null; then
+		echo "FAIL: perf annotate --data-type $mode"
+		cleanup
+		exit 1
+	fi
+
+	if ! awk '
+		$1 + 0 > 0 && /struct flex/ { total = $1 + 0 }
+		/char\[\]/ && /data;/ { data = $1 + 0 }
+		END { exit !(total > 0 && total == data) }
+	' <(sed -n "/^Annotate type: 'struct flex' in/,/^Annotate type: /p" "$perfout"); then
+		echo "FAIL: --data-type $mode does not count the flexible array accesses"
+		cleanup
+		exit 1
+	fi
+done
+
+echo "flexible array member resolved and counted"
 cleanup
diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index dd9c1d7b2da8be8a..7fae186ffd76b533 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -2233,6 +2233,25 @@ static void print_annotated_data_value(struct type_hist *h, u64 period, int nr_s
 		color_fprintf(stdout, color, " %7.2f", percent);
 }
 
+/*
+ * A flexible array member is resolved past the end of its parent, so the
+ * parent's samples are not bounded by its size.
+ */
+static int member_extent(struct annotated_member *member)
+{
+	struct annotated_member *child;
+	int end = member->offset + member->size;
+
+	list_for_each_entry(child, &member->children, node) {
+		int child_end = member_extent(child);
+
+		if (child_end > end)
+			end = child_end;
+	}
+
+	return end;
+}
+
 static void print_annotated_data_type(struct annotated_data_type *mem_type,
 				      struct annotated_member *member,
 				      struct evsel *evsel, int indent)
@@ -2240,6 +2259,7 @@ static void print_annotated_data_type(struct annotated_data_type *mem_type,
 	struct annotated_member *child;
 	struct type_hist *h;
 	int i, nr_events = 0, samples = 0;
+	int end = member_extent(member);
 	u64 period = 0;
 	int width = symbol_conf.show_total_period ? 11 : 7;
 	struct evsel *pos;
@@ -2253,10 +2273,10 @@ static void print_annotated_data_type(struct annotated_data_type *mem_type,
 
 		samples = 0;
 		period = 0;
-		for (i = 0; i < member->size; i++) {
+		for (i = member->offset; i < end; i++) {
 			struct type_hist_entry *entry;
 
-			if (!hashmap__find(&h->samples, member->offset + i, &entry))
+			if (!hashmap__find(&h->samples, i, &entry))
 				continue;
 
 			samples += entry->nr_samples;
-- 
2.56.0