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.
46extern "C" {
47__declspec(dllimport) int __asan_should_detect_stack_use_after_return();
48int __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.
61extern "C" void __cdecl _initterm(void *a, void *b);
62
63namespace {
64__declspec(allocate(".CRT$XTW")) void* before_global_dtors = 0;
65__declspec(allocate(".CRT$XTY")) void* after_global_dtors = 0;
66
67void UnregisterGlobals() {
68  _initterm(&before_global_dtors, &after_global_dtors);
69}
70
71int 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"))
80int (*__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).
88extern "C" {
89__declspec(dllimport) int __asan_set_seh_filter();
90static 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