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