[wasm] Add guard regions to end of WebAssembly.Memory buffers

src/base/platform/platform.h

Index: src/base/platform/platform.h
diff --git a/src/base/platform/platform.h b/src/base/platform/platform.h
index 5d570e7048b6d1fc4b600cfd3f9e38ba397e4a18..374cddfc0c39c989adce633cda4c33ca07acdbb9 100644
--- a/src/base/platform/platform.h
+++ b/src/base/platform/platform.h
@@ -178,6 +178,11 @@ class V8_BASE_EXPORT OS {
                         bool is_executable);
   static void Free(void* address, const size_t size);
 
+  // Allocates a region of memory that is inaccessible. On Windows this reserves
+  // but does not commit the memory. On Linux, it is equivalent to a call to
+  // Allocate() followed by Guard().
+  static void* AllocateGuarded(const size_t requested);
+
   // This is the granularity at which the ProtectCode(...) call can set page
   // permissions.
   static intptr_t CommitPageSize();
@@ -188,6 +193,9 @@ class V8_BASE_EXPORT OS {
   // Assign memory as a guard page so that access will cause an exception.
   static void Guard(void* address, const size_t size);
 
+  // Make a region of memory readable and writable.
+  static void Unprotect(void* address, const size_t size);
+
   // Generate a random address to be used for hinting mmap().
   static void* GetRandomMmapAddr();