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 <string>
14
15#include "llvm/ADT/STLExtras.h"
16
17namespace llvm {
18class StringRef;
19
20class CrashRecoveryContextCleanup;
21
22/// \brief Crash recovery helper object.
23///
24/// This class implements support for running operations in a safe context so
25/// that crashes (memory errors, stack overflow, assertion violations) can be
26/// detected and control restored to the crashing thread. Crash detection is
27/// purely "best effort", the exact set of failures which can be recovered from
28/// is platform dependent.
29///
30/// Clients make use of this code by first calling
31/// CrashRecoveryContext::Enable(), and then executing unsafe operations via a
32/// CrashRecoveryContext object. For example:
33///
34///    void actual_work(void *);
35///
36///    void foo() {
37///      CrashRecoveryContext CRC;
38///
39///      if (!CRC.RunSafely(actual_work, 0)) {
40///         ... a crash was detected, report error to user ...
41///      }
42///
43///      ... no crash was detected ...
44///    }
45///
46/// Crash recovery contexts may not be nested.
47class CrashRecoveryContext {
48  void *Impl;
49  CrashRecoveryContextCleanup *head;
50
51public:
52  CrashRecoveryContext() : Impl(nullptr), head(nullptr) {}
53  ~CrashRecoveryContext();
54
55  void registerCleanup(CrashRecoveryContextCleanup *cleanup);
56  void unregisterCleanup(CrashRecoveryContextCleanup *cleanup);
57
58  /// \brief Enable crash recovery.
59  static void Enable();
60
61  /// \brief Disable crash recovery.
62  static void Disable();
63
64  /// \brief Return the active context, if the code is currently executing in a
65  /// thread which is in a protected context.
66  static CrashRecoveryContext *GetCurrent();
67
68  /// \brief Return true if the current thread is recovering from a
69  /// crash.
70  static bool isRecoveringFromCrash();
71
72  /// \brief Execute the provide callback function (with the given arguments) in
73  /// a protected context.
74  ///
75  /// \return True if the function completed successfully, and false if the
76  /// function crashed (or HandleCrash was called explicitly). Clients should
77  /// make as little assumptions as possible about the program state when
78  /// RunSafely has returned false. Clients can use getBacktrace() to retrieve
79  /// the backtrace of the crash on failures.
80  bool RunSafely(function_ref<void()> Fn);
81  bool RunSafely(void (*Fn)(void*), void *UserData) {
82    return RunSafely([&]() { Fn(UserData); });
83  }
84
85  /// \brief Execute the provide callback function (with the given arguments) in
86  /// a protected context which is run in another thread (optionally with a
87  /// requested stack size).
88  ///
89  /// See RunSafely() and llvm_execute_on_thread().
90  ///
91  /// On Darwin, if PRIO_DARWIN_BG is set on the calling thread, it will be
92  /// propagated to the new thread as well.
93  bool RunSafelyOnThread(function_ref<void()>, unsigned RequestedStackSize = 0);
94  bool RunSafelyOnThread(void (*Fn)(void*), void *UserData,
95                         unsigned RequestedStackSize = 0) {
96    return RunSafelyOnThread([&]() { Fn(UserData); }, RequestedStackSize);
97  }
98
99  /// \brief Explicitly trigger a crash recovery in the current process, and
100  /// return failure from RunSafely(). This function does not return.
101  void HandleCrash();
102
103  /// \brief Return a string containing the backtrace where the crash was
104  /// detected; or empty if the backtrace wasn't recovered.
105  ///
106  /// This function is only valid when a crash has been detected (i.e.,
107  /// RunSafely() has returned false.
108  const std::string &getBacktrace() const;
109};
110
111class CrashRecoveryContextCleanup {
112protected:
113  CrashRecoveryContext *context;
114  CrashRecoveryContextCleanup(CrashRecoveryContext *context)
115    : context(context), cleanupFired(false) {}
116public:
117  bool cleanupFired;
118
119  virtual ~CrashRecoveryContextCleanup();
120  virtual void recoverResources() = 0;
121
122  CrashRecoveryContext *getContext() const {
123    return context;
124  }
125
126private:
127  friend class CrashRecoveryContext;
128  CrashRecoveryContextCleanup *prev, *next;
129};
130
131template<typename DERIVED, typename T>
132class CrashRecoveryContextCleanupBase : public CrashRecoveryContextCleanup {
133protected:
134  T *resource;
135  CrashRecoveryContextCleanupBase(CrashRecoveryContext *context, T* resource)
136    : CrashRecoveryContextCleanup(context), resource(resource) {}
137public:
138  static DERIVED *create(T *x) {
139    if (x) {
140      if (CrashRecoveryContext *context = CrashRecoveryContext::GetCurrent())
141        return new DERIVED(context, x);
142    }
143    return 0;
144  }
145};
146
147template <typename T>
148class CrashRecoveryContextDestructorCleanup : public
149  CrashRecoveryContextCleanupBase<CrashRecoveryContextDestructorCleanup<T>, T> {
150public:
151  CrashRecoveryContextDestructorCleanup(CrashRecoveryContext *context,
152                                        T *resource)
153    : CrashRecoveryContextCleanupBase<
154        CrashRecoveryContextDestructorCleanup<T>, T>(context, resource) {}
155
156  virtual void recoverResources() {
157    this->resource->~T();
158  }
159};
160
161template <typename T>
162class CrashRecoveryContextDeleteCleanup : public
163  CrashRecoveryContextCleanupBase<CrashRecoveryContextDeleteCleanup<T>, T> {
164public:
165  CrashRecoveryContextDeleteCleanup(CrashRecoveryContext *context, T *resource)
166    : CrashRecoveryContextCleanupBase<
167        CrashRecoveryContextDeleteCleanup<T>, T>(context, resource) {}
168
169  virtual void recoverResources() {
170    delete this->resource;
171  }
172};
173
174template <typename T>
175class CrashRecoveryContextReleaseRefCleanup : public
176  CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T>
177{
178public:
179  CrashRecoveryContextReleaseRefCleanup(CrashRecoveryContext *context,
180                                        T *resource)
181    : CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>,
182          T>(context, resource) {}
183
184  virtual void recoverResources() {
185    this->resource->Release();
186  }
187};
188
189template <typename T, typename Cleanup = CrashRecoveryContextDeleteCleanup<T> >
190class CrashRecoveryContextCleanupRegistrar {
191  CrashRecoveryContextCleanup *cleanup;
192public:
193  CrashRecoveryContextCleanupRegistrar(T *x)
194    : cleanup(Cleanup::create(x)) {
195    if (cleanup)
196      cleanup->getContext()->registerCleanup(cleanup);
197  }
198
199  ~CrashRecoveryContextCleanupRegistrar() {
200    unregister();
201  }
202
203  void unregister() {
204    if (cleanup && !cleanup->cleanupFired)
205      cleanup->getContext()->unregisterCleanup(cleanup);
206    cleanup = 0;
207  }
208};
209}
210
211#endif
212