// rcu tapset
// Copyright (C) 2013, 2017 Red Hat
//
// This file is part of systemtap, and is free software.  You can
// redistribute it and/or modify it under the terms of the GNU General
// Public License (GPL); either version 2, or (at your option) any
// later version.

%{
#include <linux/rcupdate.h>
%}

function rcu_dereference:long (protected_pointer:long) %{ /* pure */
    void *protected_pointer = (void *)(uintptr_t)STAP_ARG_protected_pointer;
    long fetched_value;

    /* We call kderef() here to ensure the memory is valid to read.
     * Note the result is thrown away, then we use the "real"
     * rcu_dereference function now that we know the address is
     * safe. */
    (void)kderef(sizeof(*protected_pointer), protected_pointer);

    rcu_read_lock();
    fetched_value = (long)rcu_dereference(protected_pointer);
    rcu_read_unlock();
    STAP_RETVALUE = fetched_value;

    CATCH_DEREF_FAULT();
%}