Landing: Write protect executable pages in the VM.

runtime/vm/virtual_memory.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_VIRTUAL_MEMORY_H_
 #define VM_VIRTUAL_MEMORY_H_
 
 #include "platform/utils.h"
 #include "vm/globals.h"
 #include "vm/memory_region.h"
 
 namespace dart {
 
 class VirtualMemory {
  public:
+  // Read-write-execute is not available because it is never used.
   enum Protection {
     kNoAccess,
     kReadOnly,
     kReadWrite,
     kReadExecute,
-    kReadWriteExecute
   };
 
   // The reserved memory is unmapped on destruction.
   ~VirtualMemory();
 
   uword start() const { return region_.start(); }
   uword end() const { return region_.end(); }
   void* address() const { return region_.pointer(); }
   intptr_t size() const { return region_.size(); }
 
   static void InitOnce();
 
   bool Contains(uword addr) const {
     return region_.Contains(addr);
   }
 
   // Commits the virtual memory area.
   bool Commit(bool is_executable) {
     return Commit(start(), size(), is_executable);
   }
 
   // Changes the protection of the virtual memory area.
-  bool Protect(Protection mode);
+  static bool Protect(void* address, intptr_t size, Protection mode);
+  bool Protect(Protection mode) {
+    return Protect(address(), size(), mode);
+  }
 
   // Reserves a virtual memory segment with size. If a segment of the requested
   // size cannot be allocated NULL is returned.
   static VirtualMemory* Reserve(intptr_t size);
 
   // Reserves a virtual memory segment with the start address being aligned to
   // the requested power of two.
   static VirtualMemory* ReserveAligned(intptr_t size, intptr_t alignment);
 
   static intptr_t PageSize() {
     ASSERT(page_size_ != 0);
     ASSERT(Utils::IsPowerOfTwo(page_size_));
     return page_size_;
   }
 
+  static bool InSamePage(uword address0, uword address1);
+
  private:
   // Truncate this virtual memory segment.
   void Truncate(uword new_start, intptr_t size);
 
   // Free a sub segment. On operating systems that support it this
   // can give back the virtual memory to the system.
   void FreeSubSegment(void* address, intptr_t size);
 
   // This constructor is only used internally when reserving new virtual spaces.
   // It does not reserve any virtual address space on its own.
@@ skipping 15 matching lines @@
   void* reserved_pointer_;
 
   static uword page_size_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VirtualMemory);
 };
 
 }  // namespace dart
 
 #endif  // VM_VIRTUAL_MEMORY_H_