diff options
Diffstat (limited to 'backends/plugins/elf/elf-provider.cpp')
| -rw-r--r-- | backends/plugins/elf/elf-provider.cpp | 178 |
1 files changed, 177 insertions, 1 deletions
diff --git a/backends/plugins/elf/elf-provider.cpp b/backends/plugins/elf/elf-provider.cpp index 5692c8a07b..d1c8f6aa05 100644 --- a/backends/plugins/elf/elf-provider.cpp +++ b/backends/plugins/elf/elf-provider.cpp @@ -1 +1,177 @@ -dummy +/* 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. + * + * $URL$ + * $Id$ + * + */ + +#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 "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; +} + +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->discard_symtab(); + + 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; + } +} + +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) + |