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

src/wasm/wasm-module.h

Index: src/wasm/wasm-module.h
diff --git a/src/wasm/wasm-module.h b/src/wasm/wasm-module.h
index 2376a5feba889b33edd3e41e3b67dd93dfb37e94..1b2708a1c3efc21e033d57bddfa54b2f1b618f8e 100644
--- a/src/wasm/wasm-module.h
+++ b/src/wasm/wasm-module.h
@@ -36,6 +36,10 @@ const uint32_t kWasmVersion = 0x0d;
 const uint8_t kWasmFunctionTypeForm = 0x60;
 const uint8_t kWasmAnyFunctionTypeForm = 0x70;
 
+#if V8_HOST_ARCH_64_BIT

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

Any reason not to just define this on all architectures (as an int64_t)?

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

I was having a hard time finding the right incantation to make all the try bots
happy and finally just gave up. I'll try again though.

Done.

+const size_t kWasmMaxHeapOffset = static_cast<size_t>(8) << 30;  // 8GB

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

I wonder if there is a more self-explanatory calculation, for example 2 *
std::numeric_limits<uint32_t>::max() ? or 
std::numeric_limits<uint32_t>::max() // maximum offset value
+ std::numeric_limits<uint32_t>::max() // maximum index value

probably there's an even better way.

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

Done

+#endif
+
 enum WasmSectionCode {
   kUnknownSectionCode = 0,   // code for unknown sections
   kTypeSectionCode = 1,      // Function signature declarations
@@ -557,6 +561,8 @@ int32_t GetInstanceMemorySize(Isolate* isolate, Handle<JSObject> instance);
 int32_t GrowInstanceMemory(Isolate* isolate, Handle<JSObject> instance,
                            uint32_t pages);
 
+Handle<JSArrayBuffer> NewArrayBuffer(Isolate* isolate, size_t size, bool guard);
+
 namespace testing {
 
 void ValidateInstancesChain(Isolate* isolate, Handle<JSObject> wasm_module,