selftests/ftrace: Add user-memory access syntax testcase

#!/bin/sh

# SPDX-License-Identifier: GPL-2.0

# description: Kprobe event user-memory access

[ -f kprobe_events ] || exit_unsupported # this is configurable

grep -q '\$arg<N>' README || exit_unresolved # depends on arch

grep -A10 "fetcharg:" README | grep -q 'ustring' || exit_unsupported

grep -A10 "fetcharg:" README | grep -q '\[u\]<offset>' || exit_unsupported

:;: "user-memory access syntax and ustring working on user memory";:

echo 'p:myevent do_sys_open path=+0($arg2):ustring path2=+u0($arg2):string' \

	> kprobe_events

grep myevent kprobe_events | \

	grep -q 'path=+0($arg2):ustring path2=+u0($arg2):string'

echo 1 > events/kprobes/myevent/enable

echo > /dev/null

echo 0 > events/kprobes/myevent/enable

grep myevent trace | grep -q 'path="/dev/null" path2="/dev/null"'

:;: "user-memory access syntax and ustring not working with kernel memory";:

echo 'p:myevent vfs_symlink path=+0($arg3):ustring path2=+u0($arg3):string' \

	> kprobe_events

echo 1 > events/kprobes/myevent/enable

ln -s foo $TMPDIR/bar

echo 0 > events/kprobes/myevent/enable

grep myevent trace | grep -q 'path=(fault) path2=(fault)'

exit 0