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

src/wasm/wasm-js.cc

Index: src/wasm/wasm-js.cc
diff --git a/src/wasm/wasm-js.cc b/src/wasm/wasm-js.cc
index 72482388ed3099febfe994aa1b7a968270c3ab1a..ea2be67e52ba7dcaeee5fcca87a14585bc1a841c 100644
--- a/src/wasm/wasm-js.cc
+++ b/src/wasm/wasm-js.cc
@@ -228,10 +228,12 @@ void WebAssemblyInstance(const v8::FunctionCallbackInfo<v8::Value>& args) {
   }
 
   i::Handle<i::JSArrayBuffer> memory = i::Handle<i::JSArrayBuffer>::null();
-  if (args.Length() > 2 && args[2]->IsArrayBuffer()) {
+  if (args.Length() > 2 && args[2]->IsObject()) {

[Mircea Trofin, 2016/10/28 22:16:29]

please separate support for WebAssembly.Memory in a different CL.

[Eric Holk, 2016/10/29 00:04:30]

Done: https://codereview.chromium.org/2460773003/

     Local<Object> obj = Local<Object>::Cast(args[2]);
     i::Handle<i::Object> mem_obj = v8::Utils::OpenHandle(*obj);
-    memory = i::Handle<i::JSArrayBuffer>(i::JSArrayBuffer::cast(*mem_obj));
+    if (i::WasmJs::IsWasmMemoryObject(i_isolate, mem_obj)) {
+      memory = i::WasmJs::GetWasmMemoryArrayBuffer(i_isolate, mem_obj);

[titzer, 2016/10/28 16:24:57]

Can we split out the WebAssembly.Memory requirement (and changes to tests) into
another CL? That'd be easy to land first.

[Eric Holk, 2016/10/28 18:44:40]

Sure. I'll add a couple more cases to make sure we fail correctly when using a
non-WebAssembly.Memory object.

https://codereview.chromium.org/2460773003

+    }
   }
   i::MaybeHandle<i::JSObject> instance =
       i::wasm::WasmModule::Instantiate(i_isolate, &thrower, i_obj, ffi, memory);
@@ -363,11 +365,10 @@ void WebAssemblyMemory(const v8::FunctionCallbackInfo<v8::Value>& args) {
     }
   }
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
-  i::Handle<i::JSArrayBuffer> buffer =
-      i_isolate->factory()->NewJSArrayBuffer(i::SharedFlag::kNotShared);
   size_t size = static_cast<size_t>(i::wasm::WasmModule::kPageSize) *
                 static_cast<size_t>(initial);
-  i::JSArrayBuffer::SetupAllocatingData(buffer, i_isolate, size);
+  i::Handle<i::JSArrayBuffer> buffer =
+      i::wasm::NewArrayBuffer(i_isolate, size, i::FLAG_wasm_guard_pages);
 
   i::Handle<i::JSObject> memory_obj = i::WasmJs::CreateWasmMemoryObject(
       i_isolate, buffer, has_maximum.FromJust(), maximum);