Set VMTag from stubs when transitioning between Dart and Native

runtime/vm/stub_code_ia32.cc

Index: runtime/vm/stub_code_ia32.cc
diff --git a/runtime/vm/stub_code_ia32.cc b/runtime/vm/stub_code_ia32.cc
index 525e8cec7ab9c49fc56008ae3656beaf2d2f6491..8bac543f5508007c17fa1b8d7d8cdd9c6cf276ab 100644
--- a/runtime/vm/stub_code_ia32.cc
+++ b/runtime/vm/stub_code_ia32.cc
@@ -16,6 +16,7 @@
 #include "vm/scavenger.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
+#include "vm/tags.h"
 
 
 #define __ assembler->
@@ -58,6 +59,9 @@ void StubCode::GenerateCallToRuntimeStub(Assembler* assembler) {
   // Cache Isolate pointer into CTX while executing runtime code.
   __ movl(CTX, EAX);
 
+  // Mark that the isolate is executing VM code.

[siva, 2014/03/14 20:45:39]

#if defined(DEBUG)
  check that the vm_tag was kScripttagId here.
#endif

+  __ movl(Address(CTX, Isolate::vm_tag_offset()), Immediate(VMTag::kVMTagId));
+
   // Reserve space for arguments and align frame before entering C++ world.
   __ AddImmediate(ESP, Immediate(-sizeof(NativeArguments)));
   if (OS::ActivationFrameAlignment() > 1) {
@@ -75,6 +79,10 @@ void StubCode::GenerateCallToRuntimeStub(Assembler* assembler) {
   __ movl(Address(ESP, retval_offset), EAX);  // Set retval in NativeArguments.
   __ call(ECX);
 
+  // Mark that the isolate is executing Dart code.
+  __ movl(Address(CTX, Isolate::vm_tag_offset()),
+          Immediate(VMTag::kScriptTagId));
+
   // Reset exit frame information in Isolate structure.
   __ movl(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
@@ -148,6 +156,10 @@ void StubCode::GenerateCallNativeCFunctionStub(Assembler* assembler) {
   // Cache Isolate pointer into CTX while executing native code.
   __ movl(CTX, EDI);
 
+  // Mark that the isolate is executing Native code.

[siva, 2014/03/14 20:45:39]

Ditto debug assertion here.

+  __ movl(Address(CTX, Isolate::vm_tag_offset()),
+          Immediate(VMTag::kRuntimeNativeTagId));
+
   // Reserve space for the native arguments structure, the outgoing parameters
   // (pointer to the native arguments structure, the C function entry point)
   // and align frame before entering the C++ world.
@@ -177,6 +189,10 @@ void StubCode::GenerateCallNativeCFunctionStub(Assembler* assembler) {
   __ call(ECX);
   __ Bind(&done);
 
+  // Mark that the isolate is executing Dart code.
+  __ movl(Address(CTX, Isolate::vm_tag_offset()),
+          Immediate(VMTag::kScriptTagId));
+
   // Reset exit frame information in Isolate structure.
   __ movl(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
@@ -229,6 +245,10 @@ void StubCode::GenerateCallBootstrapCFunctionStub(Assembler* assembler) {
   // Cache Isolate pointer into CTX while executing native code.
   __ movl(CTX, EDI);
 
+  // Mark that the isolate is executing Native code.

[siva, 2014/03/14 20:45:39]

Ditto debug assertion here.

+  __ movl(Address(CTX, Isolate::vm_tag_offset()),
+          Immediate(VMTag::kRuntimeNativeTagId));
+
   // Reserve space for the native arguments structure, the outgoing parameter
   // (pointer to the native arguments structure) and align frame before
   // entering the C++ world.
@@ -247,6 +267,10 @@ void StubCode::GenerateCallBootstrapCFunctionStub(Assembler* assembler) {
   __ movl(Address(ESP, 0), EAX);  // Pass the pointer to the NativeArguments.
   __ call(ECX);
 
+  // Mark that the isolate is executing Dart code.
+  __ movl(Address(CTX, Isolate::vm_tag_offset()),
+          Immediate(VMTag::kScriptTagId));
+
   // Reset exit frame information in Isolate structure.
   __ movl(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
@@ -836,6 +860,15 @@ void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
   __ movl(ECX, Address(EDI, Isolate::top_context_offset()));
   __ pushl(ECX);
 
+  // Save the current VMTag on the stack.
+  ASSERT(kSavedVMTagSlotFromEntryFp == -6);
+  __ movl(ECX, Address(EDI, Isolate::vm_tag_offset()));
+  __ pushl(ECX);

[siva, 2014/03/14 20:45:39]

As discussed offline you would have to flip this slot as the
StackIterator::VisitHandles code will visit this slot currently looking for
object pointers.

[Cutch, 2014/03/17 15:46:01]

Done.

We now push in the following order:

vmtag
top_exit_frame_info
context

constants adjusted accordingly.

+
+  // Mark that the isolate is executing Dart code.
+  __ movl(Address(EDI, Isolate::vm_tag_offset()),
+          Immediate(VMTag::kScriptTagId));
+
   // Load arguments descriptor array into EDX.
   __ movl(EDX, Address(EBP, kArgumentsDescOffset));
   __ movl(EDX, Address(EDX, VMHandles::kOffsetOfRawPtrInHandle));
@@ -882,6 +915,10 @@ void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
   // Load Isolate pointer from Context structure into CTX. Drop Context.
   __ movl(CTX, FieldAddress(CTX, Context::isolate_offset()));
 
+  // Restore the current VMTag from the stack.
+  __ popl(ECX);
+  __ movl(Address(CTX, Isolate::vm_tag_offset()), ECX);
+
   // Restore the saved Context pointer into the Isolate structure.
   // Uses ECX as a temporary register for this.
   __ popl(ECX);