Add guard pages in front of platform allocations

src/platform-posix.cc

Index: src/platform-posix.cc
===================================================================
--- src/platform-posix.cc	(revision 8679)
+++ src/platform-posix.cc	(working copy)
@@ -33,6 +33,7 @@
 #include <errno.h>
 #include <time.h>
 
+#include <sys/mman.h>
 #include <sys/socket.h>
 #include <sys/resource.h>
 #include <sys/time.h>
@@ -43,6 +44,8 @@
 #include <netinet/in.h>
 #include <netdb.h>
 
+#undef MAP_TYPE
+
 #if defined(ANDROID)
 #define LOG_TAG "v8"
 #include <utils/Log.h>  // LOG_PRI_VA
@@ -67,6 +70,12 @@
 }
 
 
+// Create guard pages.
+void OS::Guard(void* address, const size_t size) {
+  mprotect(address, size, PROT_NONE);
+}
+
+
 // ----------------------------------------------------------------------------
 // Math functions