perf tests: Harden branch stack sampling test

On continuous testing the perf script output can be empty, or nearly
empty, causing tr/grep to exit and due to "set -e" the test traps and
fails.

Add some empty file handling that sets the test to skip and make grep
and other text rewriting failures non-fatal by adding "|| true".

Committer testing:

  root@number:~# grep -m1 "model name" /proc/cpuinfo
  model name	: AMD Ryzen 9 9950X3D 16-Core Processor
  root@number:~# perf test "Check branch stack sampling"
  104: Check branch stack sampling                                     : Ok
  root@number:~#
  root@number:~# perf test -vvvvvvv "Check branch stack sampling"
  104: Check branch stack sampling:
  --- start ---
  test child forked, pid 396047
   142d22-142da0 l brstack_bench
  perf does have symbol 'brstack_bench'
  Testing user branch stack sampling
  Testing branch stack filtering permutation (any_call,CALL|IND_CALL|COND_CALL|SYSCALL|IRQ)
  Testing branch stack filtering permutation (call,CALL|SYSCALL)
  Testing branch stack filtering permutation (cond,COND)
  Testing branch stack filtering permutation (any_ret,RET|COND_RET|SYSRET|ERET)
  Testing branch stack filtering permutation (call,cond,CALL|SYSCALL|COND)
  Testing branch stack filtering permutation (any_call,cond,CALL|IND_CALL|COND_CALL|IRQ|SYSCALL|COND)
  Testing branch stack filtering permutation (cond,any_call,any_ret,COND|CALL|IND_CALL|COND_CALL|SYSCALL|IRQ|RET|COND_RET|SYSRET|ERET)
  ---- end(0) ----
  104: Check branch stack sampling                                     : Ok
  root@number:~#

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250318161639.34446-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: captain5050

tools/perf/tests/shell/test_brstack.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # Check branch stack sampling
 
 # SPDX-License-Identifier: GPL-2.0
@@ -17,35 +17,50 @@ fi
 
 skip_test_missing_symbol brstack_bench
 
+err=0
 TMPDIR=$(mktemp -d /tmp/__perf_test.program.XXXXX)
 TESTPROG="perf test -w brstack"
 
 cleanup() {
 	rm -rf $TMPDIR
+	trap - EXIT TERM INT
 }
 
-trap cleanup EXIT TERM INT
+trap_cleanup() {
+	set +e
+	echo "Unexpected signal in ${FUNCNAME[1]}"
+	cleanup
+	exit 1
+}
+trap trap_cleanup EXIT TERM INT
 
 test_user_branches() {
 	echo "Testing user branch stack sampling"
 
-	perf record -o $TMPDIR/perf.data --branch-filter any,save_type,u -- ${TESTPROG} > /dev/null 2>&1
-	perf script -i $TMPDIR/perf.data --fields brstacksym | tr -s ' ' '\n' > $TMPDIR/perf.script
+	perf record -o "$TMPDIR/perf.data" --branch-filter any,save_type,u -- ${TESTPROG} > "$TMPDIR/record.txt" 2>&1
+	perf script -i "$TMPDIR/perf.data" --fields brstacksym > "$TMPDIR/perf.script"
 
 	# example of branch entries:
 	# 	brstack_foo+0x14/brstack_bar+0x40/P/-/-/0/CALL
 
-	set -x
-	grep -E -m1 "^brstack_bench\+[^ ]*/brstack_foo\+[^ ]*/IND_CALL/.*$"	$TMPDIR/perf.script
-	grep -E -m1 "^brstack_foo\+[^ ]*/brstack_bar\+[^ ]*/CALL/.*$"	$TMPDIR/perf.script
-	grep -E -m1 "^brstack_bench\+[^ ]*/brstack_foo\+[^ ]*/CALL/.*$"	$TMPDIR/perf.script
-	grep -E -m1 "^brstack_bench\+[^ ]*/brstack_bar\+[^ ]*/CALL/.*$"	$TMPDIR/perf.script
-	grep -E -m1 "^brstack_bar\+[^ ]*/brstack_foo\+[^ ]*/RET/.*$"		$TMPDIR/perf.script
-	grep -E -m1 "^brstack_foo\+[^ ]*/brstack_bench\+[^ ]*/RET/.*$"	$TMPDIR/perf.script
-	grep -E -m1 "^brstack_bench\+[^ ]*/brstack_bench\+[^ ]*/COND/.*$"	$TMPDIR/perf.script
-	grep -E -m1 "^brstack\+[^ ]*/brstack\+[^ ]*/UNCOND/.*$"		$TMPDIR/perf.script
-	set +x
-
+	expected=(
+		"^brstack_bench\+[^ ]*/brstack_foo\+[^ ]*/IND_CALL/.*$"
+		"^brstack_foo\+[^ ]*/brstack_bar\+[^ ]*/CALL/.*$"
+		"^brstack_bench\+[^ ]*/brstack_foo\+[^ ]*/CALL/.*$"
+		"^brstack_bench\+[^ ]*/brstack_bar\+[^ ]*/CALL/.*$"
+		"^brstack_bar\+[^ ]*/brstack_foo\+[^ ]*/RET/.*$"
+		"^brstack_foo\+[^ ]*/brstack_bench\+[^ ]*/RET/.*$"
+		"^brstack_bench\+[^ ]*/brstack_bench\+[^ ]*/COND/.*$"
+		"^brstack\+[^ ]*/brstack\+[^ ]*/UNCOND/.*$"
+	)
+	for x in "${expected[@]}"
+	do
+		if ! tr -s ' ' '\n' < "$TMPDIR/perf.script" | grep -E -m1 -q "$x"
+		then
+			echo "Branches missing $x"
+			err=1
+		fi
+	done
 	# some branch types are still not being tested:
 	# IND COND_CALL COND_RET SYSCALL SYSRET IRQ SERROR NO_TX
 }
@@ -57,14 +72,28 @@ test_filter() {
 	test_filter_expect=$2
 
 	echo "Testing branch stack filtering permutation ($test_filter_filter,$test_filter_expect)"
-
-	perf record -o $TMPDIR/perf.data --branch-filter $test_filter_filter,save_type,u -- ${TESTPROG} > /dev/null 2>&1
-	perf script -i $TMPDIR/perf.data --fields brstack | tr -s ' ' '\n' | grep '.' > $TMPDIR/perf.script
+	perf record -o "$TMPDIR/perf.data" --branch-filter "$test_filter_filter,save_type,u" -- ${TESTPROG}  > "$TMPDIR/record.txt" 2>&1
+	perf script -i "$TMPDIR/perf.data" --fields brstack > "$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 grep -E -vm1 "^[^ ]*/($test_filter_expect|-|( *))/.*$" $TMPDIR/perf.script; then
-		return 1
+	if [ ! -s "$TMPDIR/perf.script" ]
+	then
+		echo "Empty script output"
+		err=1
+		return
+	fi
+	# Look for lines not matching test_filter_expect ignoring issues caused
+	# by empty output
+	tr -s ' ' '\n' < "$TMPDIR/perf.script" | grep '.' | \
+	  grep -E -vm1 "^[^ ]*/($test_filter_expect|-|( *))/.*$" \
+	  > "$TMPDIR/perf.script-filtered" || true
+	if [ -s "$TMPDIR/perf.script-filtered" ]
+	then
+		echo "Unexpected branch filter in script output"
+		cat "$TMPDIR/perf.script"
+		err=1
+		return
 	fi
 }
 
@@ -80,3 +109,6 @@ 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|SYSCALL|COND"
 test_filter "cond,any_call,any_ret"	"COND|CALL|IND_CALL|COND_CALL|SYSCALL|IRQ|RET|COND_RET|SYSRET|ERET"
+
+cleanup
+exit $err