1//===--- CrashRecoveryContext.h - Crash Recovery ----------------*- C++ -*-===//
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#ifndef LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
11#define LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
12
13#include "llvm/ADT/STLExtras.h"
14
15namespace llvm {
16class CrashRecoveryContextCleanup;
17
18/// \brief Crash recovery helper object.
19///
20/// This class implements support for running operations in a safe context so
21/// that crashes (memory errors, stack overflow, assertion violations) can be
22/// detected and control restored to the crashing thread. Crash detection is
23/// purely "best effort", the exact set of failures which can be recovered from
24/// is platform dependent.
25///
26/// Clients make use of this code by first calling
27/// CrashRecoveryContext::Enable(), and then executing unsafe operations via a
28/// CrashRecoveryContext object. For example:
29///
30///    void actual_work(void *);
31///
32///    void foo() {
33///      CrashRecoveryContext CRC;
34///
35///      if (!CRC.RunSafely(actual_work, 0)) {
36///         ... a crash was detected, report error to user ...
37///      }
38///
39///      ... no crash was detected ...
40///    }
41class CrashRecoveryContext {
42  void *Impl;
43  CrashRecoveryContextCleanup *head;
44
45public:
46  CrashRecoveryContext() : Impl(nullptr), head(nullptr) {}
47  ~CrashRecoveryContext();
48
49  void registerCleanup(CrashRecoveryContextCleanup *cleanup);
50  void unregisterCleanup(CrashRecoveryContextCleanup *cleanup);
51
52  /// \brief Enable crash recovery.
53  static void Enable();
54
55  /// \brief Disable crash recovery.
56  static void Disable();
57
58  /// \brief Return the active context, if the code is currently executing in a
59  /// thread which is in a protected context.
60  static CrashRecoveryContext *GetCurrent();
61
62  /// \brief Return true if the current thread is recovering from a
63  /// crash.
64  static bool isRecoveringFromCrash();
65
66  /// \brief Execute the provide callback function (with the given arguments) in
67  /// a protected context.
68  ///
69  /// \return True if the function completed successfully, and false if the
70  /// function crashed (or HandleCrash was called explicitly). Clients should
71  /// make as little assumptions as possible about the program state when
72  /// RunSafely has returned false.
73  bool RunSafely(function_ref<void()> Fn);
74  bool RunSafely(void (*Fn)(void*), void *UserData) {
75    return RunSafely([&]() { Fn(UserData); });
76  }
77
78  /// \brief Execute the provide callback function (with the given arguments) in
79  /// a protected context which is run in another thread (optionally with a
80  /// requested stack size).
81  ///
82  /// See RunSafely() and llvm_execute_on_thread().
83  ///
84  /// On Darwin, if PRIO_DARWIN_BG is set on the calling thread, it will be
85  /// propagated to the new thread as well.
86  bool RunSafelyOnThread(function_ref<void()>, unsigned RequestedStackSize = 0);
87  bool RunSafelyOnThread(void (*Fn)(void*), void *UserData,
88                         unsigned RequestedStackSize = 0) {
89    return RunSafelyOnThread([&]() { Fn(UserData); }, RequestedStackSize);
90  }
91
92  /// \brief Explicitly trigger a crash recovery in the current process, and
93  /// return failure from RunSafely(). This function does not return.
94  void HandleCrash();
95};
96
97class CrashRecoveryContextCleanup {
98protected:
99  CrashRecoveryContext *context;
100  CrashRecoveryContextCleanup(CrashRecoveryContext *context)
101      : context(context), cleanupFired(false) {}
102
103public:
104  bool cleanupFired;
105
106  virtual ~CrashRecoveryContextCleanup();
107  virtual void recoverResources() = 0;
108
109  CrashRecoveryContext *getContext() const {
110    return context;
111  }
112
113private:
114  friend class CrashRecoveryContext;
115  CrashRecoveryContextCleanup *prev, *next;
116};
117
118template<typename DERIVED, typename T>
119class CrashRecoveryContextCleanupBase : public CrashRecoveryContextCleanup {
120protected:
121  T *resource;
122  CrashRecoveryContextCleanupBase(CrashRecoveryContext *context, T *resource)
123      : CrashRecoveryContextCleanup(context), resource(resource) {}
124
125public:
126  static DERIVED *create(T *x) {
127    if (x) {
128      if (CrashRecoveryContext *context = CrashRecoveryContext::GetCurrent())
129        return new DERIVED(context, x);
130    }
131    return nullptr;
132  }
133};
134
135template <typename T>
136class CrashRecoveryContextDestructorCleanup : public
137  CrashRecoveryContextCleanupBase<CrashRecoveryContextDestructorCleanup<T>, T> {
138public:
139  CrashRecoveryContextDestructorCleanup(CrashRecoveryContext *context,
140                                        T *resource)
141      : CrashRecoveryContextCleanupBase<
142            CrashRecoveryContextDestructorCleanup<T>, T>(context, resource) {}
143
144  virtual void recoverResources() {
145    this->resource->~T();
146  }
147};
148
149template <typename T>
150class CrashRecoveryContextDeleteCleanup : public
151  CrashRecoveryContextCleanupBase<CrashRecoveryContextDeleteCleanup<T>, T> {
152public:
153  CrashRecoveryContextDeleteCleanup(CrashRecoveryContext *context, T *resource)
154    : CrashRecoveryContextCleanupBase<
155        CrashRecoveryContextDeleteCleanup<T>, T>(context, resource) {}
156
157  void recoverResources() override { delete this->resource; }
158};
159
160template <typename T>
161class CrashRecoveryContextReleaseRefCleanup : public
162  CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T>
163{
164public:
165  CrashRecoveryContextReleaseRefCleanup(CrashRecoveryContext *context,
166                                        T *resource)
167    : CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>,
168          T>(context, resource) {}
169
170  void recoverResources() override { this->resource->Release(); }
171};
172
173template <typename T, typename Cleanup = CrashRecoveryContextDeleteCleanup<T> >
174class CrashRecoveryContextCleanupRegistrar {
175  CrashRecoveryContextCleanup *cleanup;
176
177public:
178  CrashRecoveryContextCleanupRegistrar(T *x)
179    : cleanup(Cleanup::create(x)) {
180    if (cleanup)
181      cleanup->getContext()->registerCleanup(cleanup);
182  }
183
184  ~CrashRecoveryContextCleanupRegistrar() { unregister(); }
185
186  void unregister() {
187    if (cleanup && !cleanup->cleanupFired)
188      cleanup->getContext()->unregisterCleanup(cleanup);
189    cleanup = nullptr;
190  }
191};
192} // end namespace llvm
193
194#endif // LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
195