[PATCH 1/1] perf test: Add branch stack sampling tests for ARM64

[German Gomez]

Adds two shell script tests in order to test branch stack sampling on
ARM64 plarforms. This functionality is enabled by the Branch Record
Buffer Extension (BRBE) on Arm.

Information about BRBE can be found in [1] chapter F1.

[1]: https://developer.arm.com/documentation/ddi0608/latest

Signed-off-by: German Gomez <german.gomez@xxxxxxx>
---
 .../perf/tests/shell/test_arm_brbe_kernel.sh  | 42 ++++++++++
 .../tests/shell/test_arm_brbe_userspace.sh    | 80 +++++++++++++++++++
 2 files changed, 122 insertions(+)
 create mode 100755 tools/perf/tests/shell/test_arm_brbe_kernel.sh
 create mode 100755 tools/perf/tests/shell/test_arm_brbe_userspace.sh

diff --git a/tools/perf/tests/shell/test_arm_brbe_kernel.sh b/tools/perf/tests/shell/test_arm_brbe_kernel.sh
new file mode 100755
index 000000000..dc5a2238f
--- /dev/null
+++ b/tools/perf/tests/shell/test_arm_brbe_kernel.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+# Arm64 BRBE kernel branches
+
+# SPDX-License-Identifier: GPL-2.0
+# German Gomez <german.gomez@xxxxxxx>, 2022
+
+PERF_DATA=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
+
+cleanup_files() {
+	rm -f $PERF_DATA*
+}
+
+trap cleanup_files exit term int
+
+test_brbe_kernel() {
+	lscpu | grep -q "aarch64" || return $?
+	perf record -o $PERF_DATA --branch-filter any,k -- true > /dev/null 2>&1
+}
+
+test_brbe_kernel || exit 2
+
+# example perf-script output:
+#   0xffffffff9a80dd5e/0xffffffff9a87c5c0/P/-/-/1
+#   0xffff8000080ac20c/0xffff800008e99720/P/-/-/2
+#   0xffff8000080ac20c/0xffff800008e99720/P/-/-/3
+
+# kernel addresses always have the upper 16 bits set (https://lwn.net/Articles/718895/)
+KERNEL_ADDRESS_REGEX="0xffff[0-9a-f]{12}"
+
+perf record -o $PERF_DATA --branch-filter any,k -a -- sleep 1
+perf script -i $PERF_DATA --fields brstack | egrep "(0x0|$KERNEL_ADDRESS_REGEX)\/(0x0|$KERNEL_ADDRESS_REGEX)\/" > /dev/null
+err=$?
+
+echo -n "BRB kernel branches: "
+if [ $err != 0 ]; then
+	echo "FAIL"
+	exit 1
+else
+	echo "PASS"
+fi
+
+exit 0
diff --git a/tools/perf/tests/shell/test_arm_brbe_userspace.sh b/tools/perf/tests/shell/test_arm_brbe_userspace.sh
new file mode 100755
index 000000000..4f0bdc03a
--- /dev/null
+++ b/tools/perf/tests/shell/test_arm_brbe_userspace.sh
@@ -0,0 +1,80 @@
+#!/bin/bash
+# Arm64 BRBE userspace branches
+
+# SPDX-License-Identifier: GPL-2.0
+# German Gomez <german.gomez@xxxxxxx>, 2022
+
+PERF_DATA=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
+TEST_PROGRAM_SOURCE=$(mktemp /tmp/brbe_test_program.XXXXX.c)
+TEST_PROGRAM=$(mktemp /tmp/brbe_test_program.XXXXX)
+
+cleanup_files() {
+	rm -f $PERF_DATA*
+	rm -f $TEST_PROGRAM_SOURCE
+	rm -f $TEST_PROGRAM
+}
+
+trap cleanup_files exit term int
+
+test_brbe_user() {
+	lscpu | grep -q "aarch64" || return $?
+	perf record -o $PERF_DATA --branch-filter any,u -- true > /dev/null 2>&1
+}
+
+test_brbe_user || exit 2
+
+# Skip if there's no compiler
+# We need it to compile the test program
+if ! [ -x "$(command -v cc)" ]; then
+	echo "failed: no compiler, install gcc"
+	exit 2
+fi
+
+script_has_branch() {
+	local from="$1\+0x[0-9a-f]+"
+	local to="$2\+0x[0-9a-f]+"
+	perf script -i $PERF_DATA --fields brstacksym | egrep -qm 1 " +$from\/$to\/"
+}
+
+# compile test program
+cat << EOF > $TEST_PROGRAM_SOURCE
+void f2() {
+}
+void f1() {
+  f2();
+}
+void f0() {
+  f1();
+  f2();
+}
+int main() {
+  while(1) {
+    f0();
+    f1();
+  }
+  return 0;
+}
+EOF
+
+CFLAGS="-O0 -fno-inline -static"
+cc $CFLAGS $TEST_PROGRAM_SOURCE -o $TEST_PROGRAM || exit 1
+
+perf record -o $PERF_DATA --branch-filter any,u -- timeout 1 $TEST_PROGRAM
+
+script_has_branch "main" "f0" &&
+	script_has_branch "main" "f1" &&
+	script_has_branch "f0" "f1" &&
+	script_has_branch "f0" "f2" &&
+	script_has_branch "f1" "f2" &&
+	script_has_branch "main" "main"
+err=$?
+
+echo -n "BRB user branches: "
+if [ $err != 0 ]; then
+	echo "FAIL"
+	exit 1
+else
+	echo "PASS"
+fi
+
+exit 0
-- 
2.25.1