[PATCH v3 04/12] perf tests: Exercise the flexible array member path

[Arnaldo Carvalho de Melo <acme@kernel.org>]

No test covered find_flex_array() and get_flex_array_member().  Add a
flex_array workload that keeps a struct with a trailing data[] behind a
global pointer, and a test that checks the accesses past the struct size
are resolved and named after the flexible array member.  The test skips
on 32-bit PIE builds, which load globals through the GOT.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/tests/builtin-test.c               |  1 +
 .../perf/tests/shell/data_type_flex_array.sh  | 70 +++++++++++++++++++
 tools/perf/tests/tests.h                      |  1 +
 tools/perf/tests/workloads/Build              |  2 +
 tools/perf/tests/workloads/flex_array.c       | 54 ++++++++++++++
 5 files changed, 128 insertions(+)
 create mode 100755 tools/perf/tests/shell/data_type_flex_array.sh
 create mode 100644 tools/perf/tests/workloads/flex_array.c

diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 299e07bd16a5a53f..18311673b231e657 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -200,6 +200,7 @@ static struct test_workload *workloads[] = {
 	&workload__callchain,
 	&workload__false_sharing,
 	&workload__global_data,
+	&workload__flex_array,
 
 #ifdef HAVE_RUST_SUPPORT
 	&workload__code_with_type,
diff --git a/tools/perf/tests/shell/data_type_flex_array.sh b/tools/perf/tests/shell/data_type_flex_array.sh
new file mode 100755
index 0000000000000000..8d6b277991aea96e
--- /dev/null
+++ b/tools/perf/tests/shell/data_type_flex_array.sh
@@ -0,0 +1,70 @@
+#!/bin/bash
+# perf data type profiling tests for flexible array members
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+perfdata=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
+perfout=$(mktemp /tmp/__perf_test.perf.out.XXXXX)
+
+cleanup()
+{
+	rm -f "$perfdata" "$perfout"
+	trap - EXIT TERM INT
+}
+
+trap_cleanup()
+{
+	echo "Unexpected signal in ${FUNCNAME[1]}"
+	cleanup
+	exit 1
+}
+trap trap_cleanup EXIT TERM INT
+
+if ! perf check feature -q dwarf; then
+	echo "Skip: no DWARF (libdw) support"
+	cleanup
+	exit 2
+fi
+
+# 32-bit PIE loads globals through the GOT, which the resolver does not follow
+if [ "$(getconf LONG_BIT)" = 32 ] &&
+   [ "$(od -An -tx1 -j16 -N2 "$(command -v perf)" | awk '{print $1}')" = 03 ]; then
+	echo "Skip: 32-bit PIE uses GOT-relative global accesses"
+	cleanup
+	exit 2
+fi
+
+# No point in recording if the PMU cannot do memory events.
+if perf mem record -o /dev/null -- true 2>&1 | \
+		grep -q "failed: no PMU supports the memory events"; then
+	cleanup
+	exit 2
+fi
+if ! perf mem record -o /dev/null -- true 2>/dev/null; then
+	echo "Skip: cannot record memory events on this PMU"
+	cleanup
+	exit 2
+fi
+
+if ! perf mem record -o "$perfdata" -- perf test -w flex_array 1 > /dev/null 2>&1; then
+	echo "FAIL: perf mem record"
+	cleanup
+	exit 1
+fi
+
+if ! perf annotate --code-with-type -i "$perfdata" --stdio \
+		--percent-limit 1 > "$perfout" 2>/dev/null; then
+	echo "FAIL: perf annotate"
+	cleanup
+	exit 1
+fi
+
+if ! grep -Fq "# data-type: struct flex +0x4 (data)" "$perfout"; then
+	echo "FAIL: flexible array member not resolved"
+	cleanup
+	exit 1
+fi
+
+echo "flexible array member resolved"
+cleanup
diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
index bbd23dd7e0455a9d..f99910b0f8d93a82 100644
--- a/tools/perf/tests/tests.h
+++ b/tools/perf/tests/tests.h
@@ -273,6 +273,7 @@ DECLARE_WORKLOAD(deterministic);
 DECLARE_WORKLOAD(callchain);
 DECLARE_WORKLOAD(false_sharing);
 DECLARE_WORKLOAD(global_data);
+DECLARE_WORKLOAD(flex_array);
 
 #ifdef HAVE_RUST_SUPPORT
 DECLARE_WORKLOAD(code_with_type);
diff --git a/tools/perf/tests/workloads/Build b/tools/perf/tests/workloads/Build
index 03017aaaaa0bec32..74a0cbe49dc93533 100644
--- a/tools/perf/tests/workloads/Build
+++ b/tools/perf/tests/workloads/Build
@@ -18,6 +18,7 @@ perf-test-y += deterministic.o
 perf-test-y += callchain.o
 perf-test-y += false_sharing.o
 perf-test-y += global_data.o
+perf-test-y += flex_array.o
 
 ifeq ($(CONFIG_RUST_SUPPORT),y)
     perf-test-y += code_with_type.o
@@ -37,3 +38,4 @@ CFLAGS_named_threads.o    = -g -O0 -fno-inline -U_FORTIFY_SOURCE
 CFLAGS_callchain.o        = -g -O0 -fno-inline -U_FORTIFY_SOURCE
 CFLAGS_false_sharing.o    = -g -O0 -fno-inline -U_FORTIFY_SOURCE
 CFLAGS_global_data.o      = -g -O0 -fno-inline -U_FORTIFY_SOURCE
+CFLAGS_flex_array.o       = -g -O0 -fno-inline -U_FORTIFY_SOURCE
diff --git a/tools/perf/tests/workloads/flex_array.c b/tools/perf/tests/workloads/flex_array.c
new file mode 100644
index 0000000000000000..20f9b0ec17969909
--- /dev/null
+++ b/tools/perf/tests/workloads/flex_array.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Flexible array member workload for data type profiling: the accesses to
+ * the array are past the end of the struct, where the resolver has to find
+ * the flexible array member.
+ *
+ * See tests/shell/data_type_flex_array.sh.
+ */
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <linux/compiler.h>
+#include "../tests.h"
+
+struct flex {
+	int len;
+	char data[];
+};
+
+static struct flex *gp;
+static volatile unsigned long flex_sink;
+static volatile sig_atomic_t done;
+
+static void sighandler(int sig __maybe_unused)
+{
+	done = 1;
+}
+
+static int flex_array(int argc, const char **argv)
+{
+	unsigned long sum = 0;
+	int sec = 1;
+
+	if (argc > 0)
+		sec = atoi(argv[0]);
+
+	gp = calloc(1, sizeof(*gp) + 4096);
+	if (gp == NULL)
+		return 1;
+	gp->len = 4096;
+
+	signal(SIGINT, sighandler);
+	signal(SIGALRM, sighandler);
+	alarm(sec);
+
+	while (!done) {
+		sum += gp->data[3];
+		gp->data[5] = 1;
+	}
+	flex_sink = sum;
+	return 0;
+}
+
+DEFINE_WORKLOAD(flex_array);
-- 
2.56.0