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      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 
     15 namespace llvm {
     16 class 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 ///    }
     41 class CrashRecoveryContext {
     42   void *Impl;
     43   CrashRecoveryContextCleanup *head;
     44 
     45 public:
     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 
     97 class CrashRecoveryContextCleanup {
     98 protected:
     99   CrashRecoveryContext *context;
    100   CrashRecoveryContextCleanup(CrashRecoveryContext *context)
    101       : context(context), cleanupFired(false) {}
    102 
    103 public:
    104   bool cleanupFired;
    105 
    106   virtual ~CrashRecoveryContextCleanup();
    107   virtual void recoverResources() = 0;
    108 
    109   CrashRecoveryContext *getContext() const {
    110     return context;
    111   }
    112 
    113 private:
    114   friend class CrashRecoveryContext;
    115   CrashRecoveryContextCleanup *prev, *next;
    116 };
    117 
    118 template<typename DERIVED, typename T>
    119 class CrashRecoveryContextCleanupBase : public CrashRecoveryContextCleanup {
    120 protected:
    121   T *resource;
    122   CrashRecoveryContextCleanupBase(CrashRecoveryContext *context, T *resource)
    123       : CrashRecoveryContextCleanup(context), resource(resource) {}
    124 
    125 public:
    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 
    135 template <typename T>
    136 class CrashRecoveryContextDestructorCleanup : public
    137   CrashRecoveryContextCleanupBase<CrashRecoveryContextDestructorCleanup<T>, T> {
    138 public:
    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 
    149 template <typename T>
    150 class CrashRecoveryContextDeleteCleanup : public
    151   CrashRecoveryContextCleanupBase<CrashRecoveryContextDeleteCleanup<T>, T> {
    152 public:
    153   CrashRecoveryContextDeleteCleanup(CrashRecoveryContext *context, T *resource)
    154     : CrashRecoveryContextCleanupBase<
    155         CrashRecoveryContextDeleteCleanup<T>, T>(context, resource) {}
    156 
    157   void recoverResources() override { delete this->resource; }
    158 };
    159 
    160 template <typename T>
    161 class CrashRecoveryContextReleaseRefCleanup : public
    162   CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T>
    163 {
    164 public:
    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 
    173 template <typename T, typename Cleanup = CrashRecoveryContextDeleteCleanup<T> >
    174 class CrashRecoveryContextCleanupRegistrar {
    175   CrashRecoveryContextCleanup *cleanup;
    176 
    177 public:
    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