| // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // Windows doesn't support pthread_key_create's destr_function, and in fact |
| // it's a bit tricky to get code to run when a thread exits. This is |
| // cargo-cult magic from http://www.codeproject.com/threads/tls.asp. |
| // We are trying to be compatible with both a LoadLibrary style invocation, as |
| // well as static linking. This code only needs to be included if we use |
| // LoadLibrary, but it hooks into the "standard" set of TLS callbacks that are |
| // provided for static linking. |
| |
| // This code is deliberately written to match the style of calls seen in |
| // base/threading/thread_local_storage_win.cc. Please keep the two in sync if |
| // coding conventions are changed. |
| |
| // WARNING: Do *NOT* try to include this in the construction of the base |
| // library, even though it potentially drives code in |
| // base/threading/thread_local_storage_win.cc. If you do, some users will end |
| // up getting duplicate definition of DllMain() in some of their later links. |
| |
| // Force a reference to _tls_used to make the linker create the TLS directory |
| // if it's not already there (that is, even if __declspec(thread) is not used). |
| // Force a reference to p_thread_callback_dllmain_typical_entry to prevent whole |
| // program optimization from discarding the variables. |
| |
| #include <windows.h> |
| |
| #include "base/compiler_specific.h" |
| #include "base/win/win_util.h" |
| |
| // Indicate if another service is scanning the callbacks. When this becomes |
| // set to true, then DllMain() will stop supporting the callback service. This |
| // value is set to true the first time any of our callbacks are called, as that |
| // shows that some other service is handling callbacks. |
| static bool linker_notifications_are_active = false; |
| |
| // This will be our mostly no-op callback that we'll list. We won't |
| // deliberately call it, and if it is called, that means we don't need to do any |
| // of the callbacks anymore. We expect such a call to arrive via a |
| // THREAD_ATTACH message, long before we'd have to perform our THREAD_DETACH |
| // callbacks. |
| static void NTAPI on_callback(PVOID h, DWORD reason, PVOID reserved); |
| |
| #ifdef _WIN64 |
| |
| #pragma comment(linker, "/INCLUDE:_tls_used") |
| #pragma comment(linker, "/INCLUDE:p_thread_callback_dllmain_typical_entry") |
| |
| #else // _WIN64 |
| |
| #pragma comment(linker, "/INCLUDE:__tls_used") |
| #pragma comment(linker, "/INCLUDE:_p_thread_callback_dllmain_typical_entry") |
| |
| #endif // _WIN64 |
| |
| // Explicitly depend on VC\crt\src\tlssup.c variables |
| // to bracket the list of TLS callbacks. |
| extern "C" PIMAGE_TLS_CALLBACK __xl_a, __xl_z; |
| |
| // extern "C" suppresses C++ name mangling so we know the symbol names for the |
| // linker /INCLUDE:symbol pragmas above. |
| extern "C" { |
| #ifdef _WIN64 |
| |
| // .CRT section is merged with .rdata on x64 so it must be constant data. |
| #pragma data_seg(push, old_seg) |
| // Use a typical possible name in the .CRT$XL? list of segments. |
| #pragma const_seg(".CRT$XLB") |
| // When defining a const variable, it must have external linkage to be sure the |
| // linker doesn't discard it. |
| extern const PIMAGE_TLS_CALLBACK p_thread_callback_dllmain_typical_entry; |
| const PIMAGE_TLS_CALLBACK p_thread_callback_dllmain_typical_entry = on_callback; |
| #pragma data_seg(pop, old_seg) |
| |
| #else // _WIN64 |
| |
| #pragma data_seg(push, old_seg) |
| // Use a typical possible name in the .CRT$XL? list of segments. |
| #pragma data_seg(".CRT$XLB") |
| PIMAGE_TLS_CALLBACK p_thread_callback_dllmain_typical_entry = on_callback; |
| #pragma data_seg(pop, old_seg) |
| |
| #endif // _WIN64 |
| } // extern "C" |
| |
| // Custom crash code to get a unique entry in crash reports. |
| NOINLINE static void CrashOnProcessDetach() { |
| *static_cast<volatile int*>(0) = 0x356; |
| } |
| |
| // Make DllMain call the listed callbacks. This way any third parties that are |
| // linked in will also be called. |
| BOOL WINAPI DllMain(PVOID h, DWORD reason, PVOID reserved) { |
| if (DLL_PROCESS_DETACH == reason && base::win::ShouldCrashOnProcessDetach()) |
| CrashOnProcessDetach(); |
| |
| if (DLL_THREAD_DETACH != reason && DLL_PROCESS_DETACH != reason) |
| return true; // We won't service THREAD_ATTACH calls. |
| |
| if (linker_notifications_are_active) |
| return true; // Some other service is doing this work. |
| |
| for (PIMAGE_TLS_CALLBACK* it = &__xl_a; it < &__xl_z; ++it) { |
| if (*it == NULL || *it == on_callback) |
| continue; // Don't bother to call our own callback. |
| (*it)(h, reason, reserved); |
| } |
| return true; |
| } |
| |
| static void NTAPI on_callback(PVOID h, DWORD reason, PVOID reserved) { |
| // Do nothing. We were just a place holder in the list used to test that we |
| // call all items. |
| // If we are called, it means that some other system is scanning the callbacks |
| // and we don't need to do so in DllMain(). |
| linker_notifications_are_active = true; |
| // Note: If some other routine some how plays this same game... we could both |
| // decide not to do the scanning <sigh>, but this trick should suppress |
| // duplicate calls on Vista, where the runtime takes care of the callbacks, |
| // and allow us to do the callbacks on XP, where we are currently devoid of |
| // callbacks (due to an explicit LoadLibrary call). |
| } |