1 // Copyright 2014 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef V8_EXECUTION_H_
6 #define V8_EXECUTION_H_
7 
8 #include "src/base/atomicops.h"
9 #include "src/globals.h"
10 
11 namespace v8 {
12 namespace internal {
13 
14 template <typename T>
15 class Handle;
16 
17 class Execution final : public AllStatic {
18  public:
19   // Whether to report pending messages, or keep them pending on the isolate.
20   enum class MessageHandling { kReport, kKeepPending };
21   enum class Target { kCallable, kRunMicrotasks };
22 
23   // Call a function, the caller supplies a receiver and an array
24   // of arguments.
25   //
26   // When the function called is not in strict mode, receiver is
27   // converted to an object.
28   //
29   V8_EXPORT_PRIVATE V8_WARN_UNUSED_RESULT static MaybeHandle<Object> Call(
30       Isolate* isolate, Handle<Object> callable, Handle<Object> receiver,
31       int argc, Handle<Object> argv[]);
32 
33   // Construct object from function, the caller supplies an array of
34   // arguments.
35   V8_WARN_UNUSED_RESULT static MaybeHandle<Object> New(
36       Isolate* isolate, Handle<Object> constructor, int argc,
37       Handle<Object> argv[]);
38   V8_WARN_UNUSED_RESULT static MaybeHandle<Object> New(
39       Isolate* isolate, Handle<Object> constructor, Handle<Object> new_target,
40       int argc, Handle<Object> argv[]);
41 
42   // Call a function, just like Call(), but handle don't report exceptions
43   // externally.
44   // The return value is either the result of calling the function (if no
45   // exception occurred), or an empty handle.
46   // If message_handling is MessageHandling::kReport, exceptions (except for
47   // termination exceptions) will be stored in exception_out (if not a
48   // nullptr).
49   static MaybeHandle<Object> TryCall(Isolate* isolate, Handle<Object> callable,
50                                      Handle<Object> receiver, int argc,
51                                      Handle<Object> argv[],
52                                      MessageHandling message_handling,
53                                      MaybeHandle<Object>* exception_out,
54                                      Target target = Target::kCallable);
55   // Convenience method for performing RunMicrotasks
56   static MaybeHandle<Object> RunMicrotasks(Isolate* isolate,
57                                            MessageHandling message_handling,
58                                            MaybeHandle<Object>* exception_out);
59 };
60 
61 
62 class ExecutionAccess;
63 class InterruptsScope;
64 
65 // StackGuard contains the handling of the limits that are used to limit the
66 // number of nested invocations of JavaScript and the stack size used in each
67 // invocation.
68 class V8_EXPORT_PRIVATE StackGuard final {
69  public:
70   // Pass the address beyond which the stack should not grow.  The stack
71   // is assumed to grow downwards.
72   void SetStackLimit(uintptr_t limit);
73 
74   // The simulator uses a separate JS stack. Limits on the JS stack might have
75   // to be adjusted in order to reflect overflows of the C stack, because we
76   // cannot rely on the interleaving of frames on the simulator.
77   void AdjustStackLimitForSimulator();
78 
79   // Threading support.
80   char* ArchiveStackGuard(char* to);
81   char* RestoreStackGuard(char* from);
ArchiveSpacePerThread()82   static int ArchiveSpacePerThread() { return sizeof(ThreadLocal); }
83   void FreeThreadResources();
84   // Sets up the default stack guard for this thread if it has not
85   // already been set up.
86   void InitThread(const ExecutionAccess& lock);
87   // Clears the stack guard for this thread so it does not look as if
88   // it has been set up.
89   void ClearThread(const ExecutionAccess& lock);
90 
91 #define INTERRUPT_LIST(V)                       \
92   V(DEBUGBREAK, DebugBreak, 0)                  \
93   V(TERMINATE_EXECUTION, TerminateExecution, 1) \
94   V(GC_REQUEST, GC, 2)                          \
95   V(INSTALL_CODE, InstallCode, 3)               \
96   V(API_INTERRUPT, ApiInterrupt, 4)             \
97   V(DEOPT_MARKED_ALLOCATION_SITES, DeoptMarkedAllocationSites, 5)
98 
99 #define V(NAME, Name, id)                                                    \
100   inline bool Check##Name() { return CheckInterrupt(NAME); }                 \
101   inline bool CheckAndClear##Name() { return CheckAndClearInterrupt(NAME); } \
102   inline void Request##Name() { RequestInterrupt(NAME); }                    \
103   inline void Clear##Name() { ClearInterrupt(NAME); }
104   INTERRUPT_LIST(V)
105 #undef V
106 
107   // Flag used to set the interrupt causes.
108   enum InterruptFlag {
109   #define V(NAME, Name, id) NAME = (1 << id),
110     INTERRUPT_LIST(V)
111   #undef V
112   #define V(NAME, Name, id) NAME |
113     ALL_INTERRUPTS = INTERRUPT_LIST(V) 0
114   #undef V
115   };
116 
climit()117   uintptr_t climit() { return thread_local_.climit(); }
jslimit()118   uintptr_t jslimit() { return thread_local_.jslimit(); }
119   // This provides an asynchronous read of the stack limits for the current
120   // thread.  There are no locks protecting this, but it is assumed that you
121   // have the global V8 lock if you are using multiple V8 threads.
real_climit()122   uintptr_t real_climit() {
123     return thread_local_.real_climit_;
124   }
real_jslimit()125   uintptr_t real_jslimit() {
126     return thread_local_.real_jslimit_;
127   }
address_of_jslimit()128   Address address_of_jslimit() {
129     return reinterpret_cast<Address>(&thread_local_.jslimit_);
130   }
address_of_real_jslimit()131   Address address_of_real_jslimit() {
132     return reinterpret_cast<Address>(&thread_local_.real_jslimit_);
133   }
134 
135   // If the stack guard is triggered, but it is not an actual
136   // stack overflow, then handle the interruption accordingly.
137   Object* HandleInterrupts();
138 
139  private:
140   StackGuard();
141 
142   bool CheckInterrupt(InterruptFlag flag);
143   void RequestInterrupt(InterruptFlag flag);
144   void ClearInterrupt(InterruptFlag flag);
145   bool CheckAndClearInterrupt(InterruptFlag flag);
146 
147   // You should hold the ExecutionAccess lock when calling this method.
has_pending_interrupts(const ExecutionAccess & lock)148   bool has_pending_interrupts(const ExecutionAccess& lock) {
149     return thread_local_.interrupt_flags_ != 0;
150   }
151 
152   // You should hold the ExecutionAccess lock when calling this method.
153   inline void set_interrupt_limits(const ExecutionAccess& lock);
154 
155   // Reset limits to actual values. For example after handling interrupt.
156   // You should hold the ExecutionAccess lock when calling this method.
157   inline void reset_limits(const ExecutionAccess& lock);
158 
159   // Enable or disable interrupts.
160   void EnableInterrupts();
161   void DisableInterrupts();
162 
163 #if V8_TARGET_ARCH_64_BIT
164   static const uintptr_t kInterruptLimit = uintptr_t{0xfffffffffffffffe};
165   static const uintptr_t kIllegalLimit = uintptr_t{0xfffffffffffffff8};
166 #else
167   static const uintptr_t kInterruptLimit = 0xfffffffe;
168   static const uintptr_t kIllegalLimit = 0xfffffff8;
169 #endif
170 
171   void PushInterruptsScope(InterruptsScope* scope);
172   void PopInterruptsScope();
173 
174   class ThreadLocal final {
175    public:
ThreadLocal()176     ThreadLocal() { Clear(); }
177     // You should hold the ExecutionAccess lock when you call Initialize or
178     // Clear.
179     void Clear();
180 
181     // Returns true if the heap's stack limits should be set, false if not.
182     bool Initialize(Isolate* isolate);
183 
184     // The stack limit is split into a JavaScript and a C++ stack limit. These
185     // two are the same except when running on a simulator where the C++ and
186     // JavaScript stacks are separate. Each of the two stack limits have two
187     // values. The one eith the real_ prefix is the actual stack limit
188     // set for the VM. The one without the real_ prefix has the same value as
189     // the actual stack limit except when there is an interruption (e.g. debug
190     // break or preemption) in which case it is lowered to make stack checks
191     // fail. Both the generated code and the runtime system check against the
192     // one without the real_ prefix.
193     uintptr_t real_jslimit_;  // Actual JavaScript stack limit set for the VM.
194     uintptr_t real_climit_;  // Actual C++ stack limit set for the VM.
195 
196     // jslimit_ and climit_ can be read without any lock.
197     // Writing requires the ExecutionAccess lock.
198     base::AtomicWord jslimit_;
199     base::AtomicWord climit_;
200 
jslimit()201     uintptr_t jslimit() {
202       return bit_cast<uintptr_t>(base::Relaxed_Load(&jslimit_));
203     }
set_jslimit(uintptr_t limit)204     void set_jslimit(uintptr_t limit) {
205       return base::Relaxed_Store(&jslimit_,
206                                  static_cast<base::AtomicWord>(limit));
207     }
climit()208     uintptr_t climit() {
209       return bit_cast<uintptr_t>(base::Relaxed_Load(&climit_));
210     }
set_climit(uintptr_t limit)211     void set_climit(uintptr_t limit) {
212       return base::Relaxed_Store(&climit_,
213                                  static_cast<base::AtomicWord>(limit));
214     }
215 
216     InterruptsScope* interrupt_scopes_;
217     int interrupt_flags_;
218   };
219 
220   // TODO(isolates): Technically this could be calculated directly from a
221   //                 pointer to StackGuard.
222   Isolate* isolate_;
223   ThreadLocal thread_local_;
224 
225   friend class Isolate;
226   friend class StackLimitCheck;
227   friend class InterruptsScope;
228 
229   DISALLOW_COPY_AND_ASSIGN(StackGuard);
230 };
231 
232 }  // namespace internal
233 }  // namespace v8
234 
235 #endif  // V8_EXECUTION_H_
236