linux/tools/testing/selftests/ftrace/test.d/dynevent/dynevent_limitations.tc

#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
# description: Checking dynamic events limitations
# requires: dynamic_events "imm-value":README

# Max arguments limitation
MAX_ARGS=128
EXCEED_ARGS=$((MAX_ARGS + 1))

# bash and dash evaluate variables differently.
# dash will evaluate '\\' every time it is read whereas bash does not.
#
#   TEST_STRING="$TEST_STRING \\$i"
#   echo $TEST_STRING
#
# With i=123
# On bash, that will print "\123"
# but on dash, that will print the escape sequence of \123 as the \ will
# be interpreted again in the echo.
#
# Set a variable "bs" to save a double backslash, then echo that
# to "ts" to see if $ts changed or not. If it changed, it's dash,
# if not, it's bash, and then bs can equal a single backslash.
bs='\\'
ts=`echo $bs`
if [ "$ts" = '\\' ]; then
  # this is bash
  bs='\'
fi

check_max_args() { # event_header
  TEST_STRING=$1
  # Acceptable
  for i in `seq 1 $MAX_ARGS`; do
    TEST_STRING="$TEST_STRING $bs$i"
  done
  echo "$TEST_STRING" >> dynamic_events
  echo > dynamic_events
  # Error
  TEST_STRING="$TEST_STRING \\$EXCEED_ARGS"
  ! echo "$TEST_STRING" >> dynamic_events
  return 0
}

# Kprobe max args limitation
if grep -q "kprobe_events" README; then
  check_max_args "p vfs_read"
fi

# Fprobe max args limitation
if grep -q "f[:[<group>/][<event>]] <func-name>[%return] [<args>]" README; then
  check_max_args "f vfs_read"
fi

# Tprobe max args limitation
if grep -q "t[:[<group>/][<event>]] <tracepoint> [<args>]" README; then
  check_max_args "t kfree"
fi

# Uprobe max args limitation
if grep -q "uprobe_events" README; then
  check_max_args "p /bin/sh:10"
fi