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#define WIN32_LEAN_AND_MEAN
28#include <windows.h>
29
30// First, declare CRT sections we'll be using in this file
31#pragma section(".CRT$XID", long, read)  // NOLINT
32#pragma section(".CRT$XCAB", long, read)  // NOLINT
33#pragma section(".CRT$XTW", long, read)  // NOLINT
34#pragma section(".CRT$XTY", long, read)  // NOLINT
35
36////////////////////////////////////////////////////////////////////////////////
37// Define a copy of __asan_option_detect_stack_use_after_return that should be
38// used when linking an MD runtime with a set of object files on Windows.
39//
40// The ASan MD runtime dllexports '__asan_option_detect_stack_use_after_return',
41// so normally we would just dllimport it.  Unfortunately, the dllimport
42// attribute adds __imp_ prefix to the symbol name of a variable.
43// Since in general we don't know if a given TU is going to be used
44// with a MT or MD runtime and we don't want to use ugly __imp_ names on Windows
45// just to work around this issue, let's clone the a variable that is
46// constant after initialization anyways.
47extern "C" {
48__declspec(dllimport) int __asan_should_detect_stack_use_after_return();
49int __asan_option_detect_stack_use_after_return =
50    __asan_should_detect_stack_use_after_return();
51}
52
53////////////////////////////////////////////////////////////////////////////////
54// For some reason, the MD CRT doesn't call the C/C++ terminators during on DLL
55// unload or on exit.  ASan relies on LLVM global_dtors to call
56// __asan_unregister_globals on these events, which unfortunately doesn't work
57// with the MD runtime, see PR22545 for the details.
58// To work around this, for each DLL we schedule a call to UnregisterGlobals
59// using atexit() that calls a small subset of C terminators
60// where LLVM global_dtors is placed.  Fingers crossed, no other C terminators
61// are there.
62extern "C" int __cdecl atexit(void (__cdecl *f)(void));
63extern "C" void __cdecl _initterm(void *a, void *b);
64
65namespace {
66__declspec(allocate(".CRT$XTW")) void* before_global_dtors = 0;
67__declspec(allocate(".CRT$XTY")) void* after_global_dtors = 0;
68
69void UnregisterGlobals() {
70  _initterm(&before_global_dtors, &after_global_dtors);
71}
72
73int ScheduleUnregisterGlobals() {
74  return atexit(UnregisterGlobals);
75}
76
77// We need to call 'atexit(UnregisterGlobals);' as early as possible, but after
78// atexit() is initialized (.CRT$XIC).  As this is executed before C++
79// initializers (think ctors for globals), UnregisterGlobals gets executed after
80// dtors for C++ globals.
81__declspec(allocate(".CRT$XID"))
82int (*__asan_schedule_unregister_globals)() = ScheduleUnregisterGlobals;
83
84}  // namespace
85
86////////////////////////////////////////////////////////////////////////////////
87// ASan SEH handling.
88// We need to set the ASan-specific SEH handler at the end of CRT initialization
89// of each module (see also asan_win.cc).
90extern "C" {
91__declspec(dllimport) int __asan_set_seh_filter();
92static int SetSEHFilter() { return __asan_set_seh_filter(); }
93
94// Unfortunately, putting a pointer to __asan_set_seh_filter into
95// __asan_intercept_seh gets optimized out, so we have to use an extra function.
96__declspec(allocate(".CRT$XCAB")) int (*__asan_seh_interceptor)() =
97    SetSEHFilter;
98}
99
100#endif // ASAN_DYNAMIC_RUNTIME_THUNK
101