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 
16 namespace llvm {
17 class 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 class CrashRecoveryContext {
43   void *Impl;
44   CrashRecoveryContextCleanup *head;
45 
46 public:
CrashRecoveryContext()47   CrashRecoveryContext() : Impl(nullptr), head(nullptr) {}
48   ~CrashRecoveryContext();
49 
50   void registerCleanup(CrashRecoveryContextCleanup *cleanup);
51   void unregisterCleanup(CrashRecoveryContextCleanup *cleanup);
52 
53   /// \brief Enable crash recovery.
54   static void Enable();
55 
56   /// \brief Disable crash recovery.
57   static void Disable();
58 
59   /// \brief Return the active context, if the code is currently executing in a
60   /// thread which is in a protected context.
61   static CrashRecoveryContext *GetCurrent();
62 
63   /// \brief Return true if the current thread is recovering from a
64   /// crash.
65   static bool isRecoveringFromCrash();
66 
67   /// \brief Execute the provide callback function (with the given arguments) in
68   /// a protected context.
69   ///
70   /// \return True if the function completed successfully, and false if the
71   /// function crashed (or HandleCrash was called explicitly). Clients should
72   /// make as little assumptions as possible about the program state when
73   /// RunSafely has returned false. Clients can use getBacktrace() to retrieve
74   /// the backtrace of the crash on failures.
75   bool RunSafely(function_ref<void()> Fn);
RunSafely(void (* Fn)(void *),void * UserData)76   bool RunSafely(void (*Fn)(void*), void *UserData) {
77     return RunSafely([&]() { Fn(UserData); });
78   }
79 
80   /// \brief Execute the provide callback function (with the given arguments) in
81   /// a protected context which is run in another thread (optionally with a
82   /// requested stack size).
83   ///
84   /// See RunSafely() and llvm_execute_on_thread().
85   ///
86   /// On Darwin, if PRIO_DARWIN_BG is set on the calling thread, it will be
87   /// propagated to the new thread as well.
88   bool RunSafelyOnThread(function_ref<void()>, unsigned RequestedStackSize = 0);
89   bool RunSafelyOnThread(void (*Fn)(void*), void *UserData,
90                          unsigned RequestedStackSize = 0) {
91     return RunSafelyOnThread([&]() { Fn(UserData); }, RequestedStackSize);
92   }
93 
94   /// \brief Explicitly trigger a crash recovery in the current process, and
95   /// return failure from RunSafely(). This function does not return.
96   void HandleCrash();
97 
98   /// \brief Return a string containing the backtrace where the crash was
99   /// detected; or empty if the backtrace wasn't recovered.
100   ///
101   /// This function is only valid when a crash has been detected (i.e.,
102   /// RunSafely() has returned false.
103   const std::string &getBacktrace() const;
104 };
105 
106 class CrashRecoveryContextCleanup {
107 protected:
108   CrashRecoveryContext *context;
CrashRecoveryContextCleanup(CrashRecoveryContext * context)109   CrashRecoveryContextCleanup(CrashRecoveryContext *context)
110       : context(context), cleanupFired(false) {}
111 
112 public:
113   bool cleanupFired;
114 
115   virtual ~CrashRecoveryContextCleanup();
116   virtual void recoverResources() = 0;
117 
getContext()118   CrashRecoveryContext *getContext() const {
119     return context;
120   }
121 
122 private:
123   friend class CrashRecoveryContext;
124   CrashRecoveryContextCleanup *prev, *next;
125 };
126 
127 template<typename DERIVED, typename T>
128 class CrashRecoveryContextCleanupBase : public CrashRecoveryContextCleanup {
129 protected:
130   T *resource;
CrashRecoveryContextCleanupBase(CrashRecoveryContext * context,T * resource)131   CrashRecoveryContextCleanupBase(CrashRecoveryContext *context, T *resource)
132       : CrashRecoveryContextCleanup(context), resource(resource) {}
133 
134 public:
create(T * x)135   static DERIVED *create(T *x) {
136     if (x) {
137       if (CrashRecoveryContext *context = CrashRecoveryContext::GetCurrent())
138         return new DERIVED(context, x);
139     }
140     return nullptr;
141   }
142 };
143 
144 template <typename T>
145 class CrashRecoveryContextDestructorCleanup : public
146   CrashRecoveryContextCleanupBase<CrashRecoveryContextDestructorCleanup<T>, T> {
147 public:
CrashRecoveryContextDestructorCleanup(CrashRecoveryContext * context,T * resource)148   CrashRecoveryContextDestructorCleanup(CrashRecoveryContext *context,
149                                         T *resource)
150       : CrashRecoveryContextCleanupBase<
151             CrashRecoveryContextDestructorCleanup<T>, T>(context, resource) {}
152 
recoverResources()153   virtual void recoverResources() {
154     this->resource->~T();
155   }
156 };
157 
158 template <typename T>
159 class CrashRecoveryContextDeleteCleanup : public
160   CrashRecoveryContextCleanupBase<CrashRecoveryContextDeleteCleanup<T>, T> {
161 public:
CrashRecoveryContextDeleteCleanup(CrashRecoveryContext * context,T * resource)162   CrashRecoveryContextDeleteCleanup(CrashRecoveryContext *context, T *resource)
163     : CrashRecoveryContextCleanupBase<
164         CrashRecoveryContextDeleteCleanup<T>, T>(context, resource) {}
165 
recoverResources()166   void recoverResources() override { delete this->resource; }
167 };
168 
169 template <typename T>
170 class CrashRecoveryContextReleaseRefCleanup : public
171   CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T>
172 {
173 public:
CrashRecoveryContextReleaseRefCleanup(CrashRecoveryContext * context,T * resource)174   CrashRecoveryContextReleaseRefCleanup(CrashRecoveryContext *context,
175                                         T *resource)
176     : CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>,
177           T>(context, resource) {}
178 
recoverResources()179   void recoverResources() override { this->resource->Release(); }
180 };
181 
182 template <typename T, typename Cleanup = CrashRecoveryContextDeleteCleanup<T> >
183 class CrashRecoveryContextCleanupRegistrar {
184   CrashRecoveryContextCleanup *cleanup;
185 
186 public:
CrashRecoveryContextCleanupRegistrar(T * x)187   CrashRecoveryContextCleanupRegistrar(T *x)
188     : cleanup(Cleanup::create(x)) {
189     if (cleanup)
190       cleanup->getContext()->registerCleanup(cleanup);
191   }
192 
~CrashRecoveryContextCleanupRegistrar()193   ~CrashRecoveryContextCleanupRegistrar() { unregister(); }
194 
unregister()195   void unregister() {
196     if (cleanup && !cleanup->cleanupFired)
197       cleanup->getContext()->unregisterCleanup(cleanup);
198     cleanup = nullptr;
199   }
200 };
201 } // end namespace llvm
202 
203 #endif // LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
204