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

src/platform-macos.cc

Index: src/platform-macos.cc
===================================================================
--- src/platform-macos.cc	(revision 1577)
+++ src/platform-macos.cc	(working copy)
@@ -231,9 +231,9 @@
 
 void* OS::Allocate(const size_t requested,
                    size_t* allocated,
-                   bool executable) {
+                   bool is_executable) {
   const size_t msize = RoundUp(requested, getpagesize());
-  int prot = PROT_READ | PROT_WRITE | (executable ? PROT_EXEC : 0);
+  int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
   void* mbase = mmap(NULL, msize, prot, MAP_PRIVATE | MAP_ANON, -1, 0);
   if (mbase == MAP_FAILED) {
     LOG(StringEvent("OS::Allocate", "mmap failed"));
@@ -245,12 +245,26 @@
 }
 
 
-void OS::Free(void* buf, const size_t length) {
+void OS::Free(void* address, const size_t size) {
   // TODO(1240712): munmap has a return value which is ignored here.
-  munmap(buf, length);
+  munmap(address, size);
 }
 
 
+#ifdef ENABLE_HEAP_PROTECTION
+
+void OS::Protect(void* address, size_t size) {
+  UNIMPLEMENTED();
+}
+
+
+void OS::Unprotect(void* address, size_t size, bool is_executable) {
+  UNIMPLEMENTED();
+}
+
+#endif
+
+
 void OS::Sleep(int milliseconds) {
   usleep(1000 * milliseconds);
 }
@@ -373,8 +387,8 @@
 }
 
 
-bool VirtualMemory::Commit(void* address, size_t size, bool executable) {
-  int prot = PROT_READ | PROT_WRITE | (executable ? PROT_EXEC : 0);
+bool VirtualMemory::Commit(void* address, size_t size, bool is_executable) {
+  int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
   if (MAP_FAILED == mmap(address, size, prot,
                          MAP_PRIVATE | MAP_ANON | MAP_FIXED,
                          kMmapFd, kMmapFdOffset)) {
@@ -392,6 +406,7 @@
               kMmapFd, kMmapFdOffset) != MAP_FAILED;
 }
 
+
 class ThreadHandle::PlatformData : public Malloced {
  public:
   explicit PlatformData(ThreadHandle::Kind kind) {