[wasm] Introduce WasmStackGuard builtin

src/runtime/runtime-wasm.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/assembler.h"
 #include "src/compiler/wasm-compiler.h"
 #include "src/conversions.h"
 #include "src/debug/debug.h"
 #include "src/factory.h"
 #include "src/frames-inl.h"
 #include "src/objects-inl.h"
+#include "src/runtime/runtime.h"
 #include "src/v8memory.h"
 #include "src/wasm/wasm-module.h"
 #include "src/wasm/wasm-objects.h"
 #include "src/wasm/wasm-opcodes.h"
 
 namespace v8 {
 namespace internal {
 
 namespace {
-Handle<WasmInstanceObject> GetWasmInstanceOnStackTop(Isolate* isolate) {
+WasmInstanceObject* GetWasmInstanceOnStackTop(Isolate* isolate) {
   DisallowHeapAllocation no_allocation;
   const Address entry = Isolate::c_entry_fp(isolate->thread_local_top());
   Address pc =
       Memory::Address_at(entry + StandardFrameConstants::kCallerPCOffset);
   Code* code = isolate->inner_pointer_to_code_cache()->GetCacheEntry(pc)->code;
   DCHECK_EQ(Code::WASM_FUNCTION, code->kind());
   WasmInstanceObject* owning_instance = wasm::GetOwningWasmInstance(code);
   CHECK_NOT_NULL(owning_instance);
-  return handle(owning_instance, isolate);
+  return owning_instance;
 }
 }  // namespace
 
 RUNTIME_FUNCTION(Runtime_WasmMemorySize) {
   HandleScope scope(isolate);
   DCHECK_EQ(0, args.length());
 
-  Handle<WasmInstanceObject> instance = GetWasmInstanceOnStackTop(isolate);
+  Handle<WasmInstanceObject> instance(GetWasmInstanceOnStackTop(isolate),
+                                      isolate);
   return *isolate->factory()->NewNumberFromInt(
       wasm::GetInstanceMemorySize(isolate, instance));
 }
 
 RUNTIME_FUNCTION(Runtime_WasmGrowMemory) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_UINT32_ARG_CHECKED(delta_pages, 0);
-  Handle<WasmInstanceObject> instance = GetWasmInstanceOnStackTop(isolate);
+  Handle<WasmInstanceObject> instance(GetWasmInstanceOnStackTop(isolate),
+                                      isolate);
   return *isolate->factory()->NewNumberFromInt(
       wasm::GrowMemory(isolate, instance, delta_pages));
 }
 
 Object* ThrowRuntimeError(Isolate* isolate, int message_id, int byte_offset,
                           bool patch_source_position) {
   HandleScope scope(isolate);
   DCHECK_NULL(isolate->context());
   StackFrameIterator it(isolate);
   it.Advance();
   CHECK(it.frame()->is_wasm_compiled());
   isolate->set_context(*WasmCompiledFrame::cast(it.frame())
                             ->wasm_instance()
                             ->compiled_module()

[ahaas, 2017/02/14 14:45:38]

Could you use GetWasmInstanceOnStackTop(isolate) here as well?

                             ->native_context());
   Handle<Object> error_obj = isolate->factory()->NewWasmRuntimeError(
       static_cast<MessageTemplate::Template>(message_id));
 
   if (!patch_source_position) {
     return isolate->Throw(*error_obj);
   }
 
   // For wasm traps, the byte offset (a.k.a source position) can not be
   // determined from relocation info, since the explicit checks for traps
@@ skipping 79 matching lines @@
   DCHECK_EQ(1, args.length());
   Object* exception = args[0];
   // The unwinder will only deliver exceptions to wasm if the exception is a
   // Number or a Smi (which we have just converted to a Number.) This logic
   // lives in Isolate::is_catchable_by_wasm(Object*).
   CHECK(exception->IsNumber());
   return exception;
 }
 
 RUNTIME_FUNCTION(Runtime_WasmRunInterpreter) {
-  DCHECK(args.length() == 3);
+  DCHECK_EQ(3, args.length());
   HandleScope scope(isolate);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, instance_obj, 0);
   CONVERT_NUMBER_CHECKED(int32_t, func_index, Int32, args[1]);
   CONVERT_ARG_HANDLE_CHECKED(Object, arg_buffer_obj, 2);
   CHECK(WasmInstanceObject::IsWasmInstanceObject(*instance_obj));
   Handle<WasmInstanceObject> instance =
       Handle<WasmInstanceObject>::cast(instance_obj);
 
   // The arg buffer is the raw pointer to the caller's stack. It looks like a
   // Smi (lowest bit not set, as checked by IsSmi), but is no valid Smi. We just
   // cast it back to the raw pointer.
   CHECK(!arg_buffer_obj->IsHeapObject());
   CHECK(arg_buffer_obj->IsSmi());
   uint8_t* arg_buffer = reinterpret_cast<uint8_t*>(*arg_buffer_obj);
 
-  // Set the current isolate's context, saving the previous one.
-  SaveContext save(isolate);
+  // Set the current isolate's context.
   isolate->set_context(*instance->compiled_module()->native_context());

[ahaas, 2017/02/14 14:45:38]

nit: Can you add a DCHECK_NULL(isolate->context()); here?

[Clemens Hammacher, 2017/02/14 17:23:14]

Done.

 
   instance->debug_info()->RunInterpreter(func_index, arg_buffer);
   return isolate->heap()->undefined_value();
 }
 
+RUNTIME_FUNCTION(Runtime_WasmStackGuard) {
+  SealHandleScope shs(isolate);
+  DCHECK_EQ(0, args.length());
+
+  // Set the current isolate's context.
+  WasmInstanceObject* instance = GetWasmInstanceOnStackTop(isolate);
+  isolate->set_context(instance->compiled_module()->ptr_to_native_context());

[ahaas, 2017/02/14 14:45:38]

nit: Can you add a DCHECK_NULL(isolate->context()); here?

[Clemens Hammacher, 2017/02/14 17:23:14]

Done.

+
+  // Check if this is a real stack overflow.
+  StackLimitCheck check(isolate);
+  if (check.JsHasOverflowed()) return isolate->StackOverflow();
+
+  return isolate->stack_guard()->HandleInterrupts();
+}
+
 }  // namespace internal
 }  // namespace v8