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