Add basic infrastructure for protecting V8's heap when leaving the VM...

src/spaces-inl.h

Index: src/spaces-inl.h
===================================================================
--- src/spaces-inl.h	(revision 1577)
+++ src/spaces-inl.h	(working copy)
@@ -219,6 +219,43 @@
 }
 
 
+bool MemoryAllocator::InInitialChunk(Address address) {
+  if (initial_chunk_ == NULL) return false;
+
+  Address start = static_cast<Address>(initial_chunk_->address());
+  return (start <= address) && (address < start + initial_chunk_->size());
+}
+
+
+#ifdef ENABLE_HEAP_PROTECTION
+
+void MemoryAllocator::Protect(Address start, size_t size) {
+  OS::Protect(start, size);
+}
+
+
+void MemoryAllocator::Unprotect(Address start,
+                                size_t size,
+                                Executability executable) {
+  OS::Unprotect(start, size, executable);
+}
+
+
+void MemoryAllocator::ProtectChunkFromPage(Page* page) {
+  int id = GetChunkId(page);
+  OS::Protect(chunks_[id].address(), chunks_[id].size());
+}
+
+
+void MemoryAllocator::UnprotectChunkFromPage(Page* page) {
+  int id = GetChunkId(page);
+  OS::Unprotect(chunks_[id].address(), chunks_[id].size(),
+                chunks_[id].owner()->executable() == EXECUTABLE);
+}
+
+#endif
+
+
 // --------------------------------------------------------------------------
 // PagedSpace