selftests/ftrace: Add max stack tracer testcase

#!/bin/sh

# SPDX-License-Identifier: GPL-2.0

# description: ftrace - Max stack tracer

# Test the basic function of max-stack usage tracing

if [ ! -f stack_trace ]; then

  echo "Max stack tracer is not supported - please make CONFIG_STACK_TRACER=y"

  exit_unsupported

fi

echo > stack_trace_filter

echo 0 > stack_max_size

echo 1 > /proc/sys/kernel/stack_tracer_enabled

: "Fork and wait for the first entry become !lock"

timeout=10

while [ $timeout -ne 0 ]; do

  ( echo "forked" )

  FL=`grep " 0)" stack_trace`

  echo $FL | grep -q "lock" || break;

  timeout=$((timeout - 1))

done

echo 0 > /proc/sys/kernel/stack_tracer_enabled

echo '*lock*' > stack_trace_filter

test `cat stack_trace_filter | wc -l` -eq `grep lock stack_trace_filter | wc -l`

echo 0 > stack_max_size

echo 1 > /proc/sys/kernel/stack_tracer_enabled

: "Fork and always the first entry including lock"

timeout=10

while [ $timeout -ne 0 ]; do

  ( echo "forked" )

  FL=`grep " 0)" stack_trace`

  echo $FL | grep -q "lock"

  timeout=$((timeout - 1))

done

echo 0 > /proc/sys/kernel/stack_tracer_enabled