1 //===-- asan_win_uar_thunk.cc ---------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file is a part of AddressSanitizer, an address sanity checker.
11 //
12 // This file defines things that need to be present in the application modules
13 // to interact with the ASan DLL runtime correctly and can't be implemented
14 // using the default "import library" generated when linking the DLL RTL.
15 //
16 // This includes:
17 // - forwarding the detect_stack_use_after_return runtime option
18 // - working around deficiencies of the MD runtime
19 // - installing a custom SEH handlerx
20 //
21 //===----------------------------------------------------------------------===//
22
23 // Only compile this code when buidling asan_dynamic_runtime_thunk.lib
24 // Using #ifdef rather than relying on Makefiles etc.
25 // simplifies the build procedure.
26 #ifdef ASAN_DYNAMIC_RUNTIME_THUNK
27 #include <windows.h>
28
29 // First, declare CRT sections we'll be using in this file
30 #pragma section(".CRT$XID", long, read) // NOLINT
31 #pragma section(".CRT$XIZ", long, read) // NOLINT
32 #pragma section(".CRT$XTW", long, read) // NOLINT
33 #pragma section(".CRT$XTY", long, read) // NOLINT
34
35 ////////////////////////////////////////////////////////////////////////////////
36 // Define a copy of __asan_option_detect_stack_use_after_return that should be
37 // used when linking an MD runtime with a set of object files on Windows.
38 //
39 // The ASan MD runtime dllexports '__asan_option_detect_stack_use_after_return',
40 // so normally we would just dllimport it. Unfortunately, the dllimport
41 // attribute adds __imp_ prefix to the symbol name of a variable.
42 // Since in general we don't know if a given TU is going to be used
43 // with a MT or MD runtime and we don't want to use ugly __imp_ names on Windows
44 // just to work around this issue, let's clone the a variable that is
45 // constant after initialization anyways.
46 extern "C" {
47 __declspec(dllimport) int __asan_should_detect_stack_use_after_return();
48 int __asan_option_detect_stack_use_after_return =
49 __asan_should_detect_stack_use_after_return();
50 }
51
52 ////////////////////////////////////////////////////////////////////////////////
53 // For some reason, the MD CRT doesn't call the C/C++ terminators during on DLL
54 // unload or on exit. ASan relies on LLVM global_dtors to call
55 // __asan_unregister_globals on these events, which unfortunately doesn't work
56 // with the MD runtime, see PR22545 for the details.
57 // To work around this, for each DLL we schedule a call to UnregisterGlobals
58 // using atexit() that calls a small subset of C terminators
59 // where LLVM global_dtors is placed. Fingers crossed, no other C terminators
60 // are there.
61 extern "C" void __cdecl _initterm(void *a, void *b);
62
63 namespace {
64 __declspec(allocate(".CRT$XTW")) void* before_global_dtors = 0;
65 __declspec(allocate(".CRT$XTY")) void* after_global_dtors = 0;
66
UnregisterGlobals()67 void UnregisterGlobals() {
68 _initterm(&before_global_dtors, &after_global_dtors);
69 }
70
ScheduleUnregisterGlobals()71 int ScheduleUnregisterGlobals() {
72 return atexit(UnregisterGlobals);
73 }
74
75 // We need to call 'atexit(UnregisterGlobals);' as early as possible, but after
76 // atexit() is initialized (.CRT$XIC). As this is executed before C++
77 // initializers (think ctors for globals), UnregisterGlobals gets executed after
78 // dtors for C++ globals.
79 __declspec(allocate(".CRT$XID"))
80 int (*__asan_schedule_unregister_globals)() = ScheduleUnregisterGlobals;
81
82 } // namespace
83
84 ////////////////////////////////////////////////////////////////////////////////
85 // ASan SEH handling.
86 // We need to set the ASan-specific SEH handler at the end of CRT initialization
87 // of each module (see also asan_win.cc).
88 extern "C" {
89 __declspec(dllimport) int __asan_set_seh_filter();
SetSEHFilter()90 static int SetSEHFilter() { return __asan_set_seh_filter(); }
91
92 // Unfortunately, putting a pointer to __asan_set_seh_filter into
93 // __asan_intercept_seh gets optimized out, so we have to use an extra function.
94 __declspec(allocate(".CRT$XIZ")) int (*__asan_seh_interceptor)() = SetSEHFilter;
95 }
96
97 #endif // ASAN_DYNAMIC_RUNTIME_THUNK
98