[PATCH] perf test: Add test for branch stack sampling

[German Gomez]

Add a self test for branch stack sampling, to check that we get the
expected branch types, and filters behave as expected.

Suggested-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Signed-off-by: German Gomez <german.gomez@xxxxxxx>
---
 tools/perf/tests/shell/lib/brstack/main.h | 16 +++++
 tools/perf/tests/shell/lib/brstack/test.c | 24 +++++++
 tools/perf/tests/shell/test_brstack.sh    | 86 +++++++++++++++++++++++
 3 files changed, 126 insertions(+)
 create mode 100644 tools/perf/tests/shell/lib/brstack/main.h
 create mode 100644 tools/perf/tests/shell/lib/brstack/test.c
 create mode 100755 tools/perf/tests/shell/test_brstack.sh

diff --git a/tools/perf/tests/shell/lib/brstack/main.h b/tools/perf/tests/shell/lib/brstack/main.h
new file mode 100644
index 000000000..94d2665ec
--- /dev/null
+++ b/tools/perf/tests/shell/lib/brstack/main.h
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0
+#define BENCH_RUNS 99999
+
+void bench(void);
+
+int main(void)
+{
+	int cnt = 0;
+
+	while (1) {
+		if ((cnt++) > BENCH_RUNS)
+			break;
+		bench();		/* call */
+	}				/* branch (uncond) */
+	return 0;
+}
diff --git a/tools/perf/tests/shell/lib/brstack/test.c b/tools/perf/tests/shell/lib/brstack/test.c
new file mode 100644
index 000000000..8a2308901
--- /dev/null
+++ b/tools/perf/tests/shell/lib/brstack/test.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "main.h"
+
+int cnt;
+
+void bar(void)
+{
+}				/* return */
+
+void foo(void)
+{
+	bar();			/* call */
+}				/* return */
+
+void bench(void)
+{
+	void (*foo_ind)(void) = foo;
+
+	if ((cnt++) % 3)	/* branch (cond) */
+		foo();		/* call */
+
+	bar();			/* call */
+	foo_ind();		/* call (ind) */
+}
diff --git a/tools/perf/tests/shell/test_brstack.sh b/tools/perf/tests/shell/test_brstack.sh
new file mode 100755
index 000000000..2b1a1b20a
--- /dev/null
+++ b/tools/perf/tests/shell/test_brstack.sh
@@ -0,0 +1,86 @@
+#!/bin/sh
+# Check branch stack sampling
+
+# SPDX-License-Identifier: GPL-2.0
+# German Gomez <german.gomez@xxxxxxx>, 2022
+
+set -e
+
+# we need a C compiler to build the test programs
+# so bail if none is found
+if ! [ -x "$(command -v cc)" ]; then
+	echo "failed: no compiler, install gcc"
+	exit 2
+fi
+
+# skip the test if the hardware doesn't support branch stack sampling
+perf record -b -o- -- true > /dev/null || exit 2
+
+TMPDIR=$(mktemp -d /tmp/__perf_test.program.XXXXX)
+
+cleanup() {
+	rm -rf $TMPDIR
+}
+
+trap cleanup exit term int
+
+test_user_branches() {
+	echo
+	echo "Testing user branch stack sampling"
+	echo
+
+	cc -fno-inline -g "$(dirname $0)/lib/brstack/test.c" -o $TMPDIR/a.out
+
+	perf record -o $TMPDIR/perf.data -q --branch-filter any,save_type,u -- $TMPDIR/a.out
+	perf script -i $TMPDIR/perf.data --fields brstacksym | xargs -n1 > $TMPDIR/perf.script
+
+	# example of branch entries:
+	# 	foo+0x14/bar+0x40/P/-/-/0/CALL
+
+	set -x
+	egrep -m1 "^bench\+[^ ]*/foo\+[^ ]*/IND_CALL$"	$TMPDIR/perf.script
+	egrep -m1 "^foo\+[^ ]*/bar\+[^ ]*/CALL$"	$TMPDIR/perf.script
+	egrep -m1 "^bench\+[^ ]*/foo\+[^ ]*/CALL$"	$TMPDIR/perf.script
+	egrep -m1 "^bench\+[^ ]*/bar\+[^ ]*/CALL$"	$TMPDIR/perf.script
+	egrep -m1 "^bar\+[^ ]*/foo\+[^ ]*/RET$"		$TMPDIR/perf.script
+	egrep -m1 "^foo\+[^ ]*/bench\+[^ ]*/RET$"	$TMPDIR/perf.script
+	egrep -m1 "^bench\+[^ ]*/bench\+[^ ]*/COND$"	$TMPDIR/perf.script
+	egrep -m1 "^main\+[^ ]*/main\+[^ ]*/UNCOND$"	$TMPDIR/perf.script
+	set +x
+
+	# some branch types are still not being tested:
+	# IND COND_CALL COND_RET SYSCALL SYSRET IRQ SERROR NO_TX
+}
+
+test_filter() {
+	local filter=$1
+	local expect=$2
+
+	echo
+	echo "Testing branch stack filtering permutation ($filter,$expect)"
+	echo
+
+	cc -fno-inline -g "$(dirname $0)/lib/brstack/test.c" -o $TMPDIR/a.out
+
+	perf record -o $TMPDIR/perf.data -q --branch-filter $filter,save_type,u -- $TMPDIR/a.out
+	perf script -i $TMPDIR/perf.data --fields brstack | xargs -n1 > $TMPDIR/perf.script
+
+	# fail if we find any branch type that doesn't match any of the expected ones
+	# also consider UNKNOWN branch types (-)
+	if egrep -vm1 "^[^ ]*/($expect|-|( *))$" $TMPDIR/perf.script; then
+		return 1
+	fi
+}
+
+test_user_branches
+
+# first argument <arg0> is the argument passed to "--branch-stack <arg0>,save_type,u"
+# second argument are the expected branch types for the given filter
+test_filter "any_call"	"CALL|IND_CALL|COND_CALL|SYSCALL|IRQ|FAULT_DATA|FAULT_INST"
+test_filter "call"	"CALL|SYSCALL"
+test_filter "cond"	"COND"
+test_filter "any_ret"	"RET|COND_RET|SYSRET|ERET"
+
+test_filter "call,cond"		"CALL|SYSCALL|COND"
+test_filter "any_call,cond"		"CALL|IND_CALL|COND_CALL|IRQ|FAULT_DATA|FAULT_INST|SYSCALL|COND"
+test_filter "cond,any_call,any_ret"	"COND|CALL|IND_CALL|COND_CALL|SYSCALL|IRQ|FAULT_DATA|FAULT_INST|RET|COND_RET|SYSRET|ERET"
-- 
2.25.1