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83 lines
2.3 KiB
C
83 lines
2.3 KiB
C
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/*
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* Copyright (C) 2020 Otto-von-Guericke-Universität Magdeburg
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup sys_cxx_ctor_guards
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* @{
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*
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* @file
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* @brief Implementation of the C++ ctor guards
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*
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* @author Marian Buschsieweke <marian.buschsieweke@ovgu.de>
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*/
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#include "test_utils/expect.h"
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#include "rmutex.h"
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#ifdef CXX_CTOR_GUARDS_CUSTOM_TYPE
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/* Some architectures (such as ARM) have custom types for __guard in their
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* ABI defined. To support such cases, a custom header can be provided and
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* `CXX_CTOR_GUARDS_CUSTOM_TYPE` can be defined */
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#include "cxx_ctor_guards_arch.h"
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#else
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/* The ABI for"generic" CPUs defines __guard as follows:
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* (see "libstdc++-v3/config/cpu/generic/cxxabi_tweaks.h" in GCC source) */
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__extension__ typedef int __guard __attribute__((mode(__DI__)));
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/* Above is just a fancy version of `typedef int64_t __guard`. But let's stick
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* with the official type definition */
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#endif
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#define GUARD_DONE 0x01
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#define GUARD_PENDING 0x02
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/* A recursive mutex is needed, as the initialization of a static class could
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* require calling ctors of members of that class. With a regular mutex, this
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* would result in a deadlock.
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*/
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static rmutex_t cxa_rmutex = RMUTEX_INIT;
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int __cxa_guard_acquire(__guard *g)
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{
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uint8_t *guard = (uint8_t *)g;
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/* Optimize for the case that the instance is already initialized by
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* doing a lock-free check. */
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if (__atomic_load_1(guard, __ATOMIC_SEQ_CST) & GUARD_DONE) {
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return 0;
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}
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rmutex_lock(&cxa_rmutex);
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/* Check again (this time protected by the rmutex) for the instance being
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* already initialized */
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if (*guard & GUARD_DONE) {
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rmutex_unlock(&cxa_rmutex);
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return 0;
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}
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if (*guard & GUARD_PENDING) {
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/* Recursive initialization of the *same* instance --> bug */
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expect(0);
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}
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*guard = GUARD_PENDING;
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return 1;
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}
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void __cxa_guard_release(__guard *g)
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{
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uint8_t *guard = (uint8_t *)g;
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*guard = GUARD_DONE;
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rmutex_unlock(&cxa_rmutex);
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}
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void __cxa_guard_abort(__guard *g)
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{
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uint8_t *guard = (uint8_t *)g;
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*guard = 0;
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rmutex_unlock(&cxa_rmutex);
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}
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