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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
#include "common/scummsys.h"
#if defined(DYNAMIC_MODULES) && defined(USE_ELF_LOADER)
#ifdef ELF_LOADER_CXA_ATEXIT
#include <cxxabi.h>
#endif
#include "backends/plugins/elf/elf-provider.h"
#include "backends/plugins/dynamic-plugin.h"
#include "backends/plugins/elf/memory-manager.h"
#include "common/debug.h"
#include "common/fs.h"
/* Note about ELF_LOADER_CXA_ATEXIT:
*
* consider the code:
*
* class Foobar {
* const char *work() {
* static String foo = "bar";
* return s.c_str();
* }
* }
*
* When instantiating Foobar and calling work() for the first time the String
* foo will be constructed. GCC automatically registers its destruction via
* either atexit() or __cxa_atexit(). Only the latter will add information
* about which DSO did the construction (Using &__dso_handle).
*
* __cxa_atexit allows plugins to reference C++ ABI symbols in the main
* executable without code duplication (No need to link the plugin against
* libstdc++), since we can distinguish which registered exit functions belong
* to a specific DSO. When unloading a plugin, we just use the C++ ABI call
* __cxa_finalize(&__dso_handle) to call all destructors of only that DSO.
*
* Prerequisites:
* - The used libc needs to support __cxa_atexit
* - -fuse-cxa-atexit in CXXFLAGS
* - Every plugin needs its own hidden __dso_handle symbol
* This is automatically done via REGISTER_PLUGIN_DYNAMIC, see base/plugins.h
*
* When __cxa_atexit can not be used, each plugin needs to link against
* libstdc++ to embed its own set of C++ ABI symbols. When not doing so,
* registered destructors of already unloaded plugins will crash the
* application upon returning from main().
*
* See "3.3.5 DSO Object Destruction API" of the C++ ABI
*/
DynamicPlugin::VoidFunc ELFPlugin::findSymbol(const char *symbol) {
void *func = 0;
if (_dlHandle)
func = _dlHandle->symbol(symbol);
if (!func) {
if (!_dlHandle)
warning("elfloader: Failed loading symbol '%s' from plugin '%s' (Handle is NULL)", symbol, _filename.c_str());
else
warning("elfloader: Failed loading symbol '%s' from plugin '%s'", symbol, _filename.c_str());
}
// FIXME HACK: This is a HACK to circumvent a clash between the ISO C++
// standard and POSIX: ISO C++ disallows casting between function pointers
// and data pointers, but dlsym always returns a void pointer. For details,
// see e.g. <http://www.trilithium.com/johan/2004/12/problem-with-dlsym/>.
assert(sizeof(VoidFunc) == sizeof(func));
VoidFunc tmp;
memcpy(&tmp, &func, sizeof(VoidFunc));
return tmp;
}
/**
* Test the size of the plugin.
*/
void ELFPlugin::trackSize() {
// All we need to do is create our object, track its size, then delete it
DLObject *obj = makeDLObject();
obj->trackSize(_filename.c_str());
delete obj;
}
bool ELFPlugin::loadPlugin() {
assert(!_dlHandle);
DLObject *obj = makeDLObject();
if (obj->open(_filename.c_str())) {
_dlHandle = obj;
} else {
delete obj;
_dlHandle = 0;
}
if (!_dlHandle) {
warning("elfloader: Failed loading plugin '%s'", _filename.c_str());
return false;
}
CharFunc buildDateFunc = (CharFunc)findSymbol("PLUGIN_getBuildDate");
if (!buildDateFunc) {
unloadPlugin();
warning("elfloader: plugin '%s' is missing symbols", _filename.c_str());
return false;
}
if (strncmp(gScummVMPluginBuildDate, buildDateFunc(), strlen(gScummVMPluginBuildDate))) {
unloadPlugin();
warning("elfloader: plugin '%s' has a different build date", _filename.c_str());
return false;
}
bool ret = DynamicPlugin::loadPlugin();
#ifdef ELF_LOADER_CXA_ATEXIT
if (ret) {
// FIXME HACK: Reverse HACK of findSymbol() :P
VoidFunc tmp;
tmp = findSymbol("__dso_handle");
memcpy(&_dso_handle, &tmp, sizeof(VoidFunc));
debug(2, "elfloader: __dso_handle is %p", _dso_handle);
}
#endif
_dlHandle->discardSymtab();
return ret;
}
void ELFPlugin::unloadPlugin() {
DynamicPlugin::unloadPlugin();
if (_dlHandle) {
#ifdef ELF_LOADER_CXA_ATEXIT
if (_dso_handle) {
debug(2, "elfloader: calling __cxa_finalize");
__cxxabiv1::__cxa_finalize(_dso_handle);
_dso_handle = 0;
}
#endif
if (!_dlHandle->close())
warning("elfloader: Failed unloading plugin '%s'", _filename.c_str());
delete _dlHandle;
_dlHandle = 0;
}
}
/**
* We override this function in FilePluginProvider to allow the single
* plugin method to create a non-fragmenting memory allocation. We take
* the plugins found and tell the memory manager to allocate space for
* them.
*/
PluginList ELFPluginProvider::getPlugins() {
PluginList pl = FilePluginProvider::getPlugins();
#if defined(UNCACHED_PLUGINS) && !defined(ELF_NO_MEM_MANAGER)
// This static downcast is safe because all of the plugins must
// be ELF plugins
for (PluginList::iterator p = pl.begin(); p != pl.end(); ++p) {
(static_cast<ELFPlugin *>(*p))->trackSize();
}
// The Memory Manager should now allocate space based on the information
// it collected
ELFMemMan.allocateHeap();
#endif
return pl;
}
bool ELFPluginProvider::isPluginFilename(const Common::FSNode &node) const {
// Check the plugin suffix
Common::String filename = node.getName();
if (!filename.hasSuffix(".PLG") && !filename.hasSuffix(".plg") &&
!filename.hasSuffix(".PLUGIN") && !filename.hasSuffix(".plugin"))
return false;
return true;
}
#endif // defined(DYNAMIC_MODULES) && defined(USE_ELF_LOADER)
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