1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "base/threading/thread_local_storage.h"
6
7 #include <windows.h>
8
9 #include "base/logging.h"
10
11 namespace base {
12
13 namespace internal {
14
AllocTLS(TLSKey * key)15 bool PlatformThreadLocalStorage::AllocTLS(TLSKey* key) {
16 TLSKey value = TlsAlloc();
17 if (value != TLS_OUT_OF_INDEXES) {
18 *key = value;
19 return true;
20 }
21 return false;
22 }
23
FreeTLS(TLSKey key)24 void PlatformThreadLocalStorage::FreeTLS(TLSKey key) {
25 BOOL ret = TlsFree(key);
26 DCHECK(ret);
27 }
28
GetTLSValue(TLSKey key)29 void* PlatformThreadLocalStorage::GetTLSValue(TLSKey key) {
30 return TlsGetValue(key);
31 }
32
SetTLSValue(TLSKey key,void * value)33 void PlatformThreadLocalStorage::SetTLSValue(TLSKey key, void* value) {
34 BOOL ret = TlsSetValue(key, value);
35 DCHECK(ret);
36 }
37
38 } // namespace internal
39
40 } // namespace base
41
42 // Thread Termination Callbacks.
43 // Windows doesn't support a per-thread destructor with its
44 // TLS primitives. So, we build it manually by inserting a
45 // function to be called on each thread's exit.
46 // This magic is from http://www.codeproject.com/threads/tls.asp
47 // and it works for VC++ 7.0 and later.
48
49 // Force a reference to _tls_used to make the linker create the TLS directory
50 // if it's not already there. (e.g. if __declspec(thread) is not used).
51 // Force a reference to p_thread_callback_base to prevent whole program
52 // optimization from discarding the variable.
53 #ifdef _WIN64
54
55 #pragma comment(linker, "/INCLUDE:_tls_used")
56 #pragma comment(linker, "/INCLUDE:p_thread_callback_base")
57
58 #else // _WIN64
59
60 #pragma comment(linker, "/INCLUDE:__tls_used")
61 #pragma comment(linker, "/INCLUDE:_p_thread_callback_base")
62
63 #endif // _WIN64
64
65 // Static callback function to call with each thread termination.
OnThreadExit(PVOID module,DWORD reason,PVOID reserved)66 void NTAPI OnThreadExit(PVOID module, DWORD reason, PVOID reserved) {
67 // On XP SP0 & SP1, the DLL_PROCESS_ATTACH is never seen. It is sent on SP2+
68 // and on W2K and W2K3. So don't assume it is sent.
69 if (DLL_THREAD_DETACH == reason || DLL_PROCESS_DETACH == reason)
70 base::internal::PlatformThreadLocalStorage::OnThreadExit();
71 }
72
73 // .CRT$XLA to .CRT$XLZ is an array of PIMAGE_TLS_CALLBACK pointers that are
74 // called automatically by the OS loader code (not the CRT) when the module is
75 // loaded and on thread creation. They are NOT called if the module has been
76 // loaded by a LoadLibrary() call. It must have implicitly been loaded at
77 // process startup.
78 // By implicitly loaded, I mean that it is directly referenced by the main EXE
79 // or by one of its dependent DLLs. Delay-loaded DLL doesn't count as being
80 // implicitly loaded.
81 //
82 // See VC\crt\src\tlssup.c for reference.
83
84 // extern "C" suppresses C++ name mangling so we know the symbol name for the
85 // linker /INCLUDE:symbol pragma above.
86 extern "C" {
87 // The linker must not discard p_thread_callback_base. (We force a reference
88 // to this variable with a linker /INCLUDE:symbol pragma to ensure that.) If
89 // this variable is discarded, the OnThreadExit function will never be called.
90 #ifdef _WIN64
91
92 // .CRT section is merged with .rdata on x64 so it must be constant data.
93 #pragma const_seg(".CRT$XLB")
94 // When defining a const variable, it must have external linkage to be sure the
95 // linker doesn't discard it.
96 extern const PIMAGE_TLS_CALLBACK p_thread_callback_base;
97 const PIMAGE_TLS_CALLBACK p_thread_callback_base = OnThreadExit;
98
99 // Reset the default section.
100 #pragma const_seg()
101
102 #else // _WIN64
103
104 #pragma data_seg(".CRT$XLB")
105 PIMAGE_TLS_CALLBACK p_thread_callback_base = OnThreadExit;
106
107 // Reset the default section.
108 #pragma data_seg()
109
110 #endif // _WIN64
111 } // extern "C"
112