Implements a new API to set a function entry hook for profiling.

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 8f316606c20d29b6889512f41939c5af1f6ecccc..f672d33e2124cf880c599cc28187b0cca234c9a4 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -470,4 +470,26 @@ void ElementsTransitionAndStoreStub::Generate(MacroAssembler* masm) {
   KeyedStoreIC::GenerateRuntimeSetProperty(masm, strict_mode_);
 }
 
+
+FunctionEntryHook ProfileEntryHookStub::entry_hook_ = NULL;
+
+
+void ProfileEntryHookStub::EntryHookTrampoline(intptr_t function,
+                                               intptr_t stack_pointer) {
+  if (entry_hook_ != NULL)
+    entry_hook_(function, stack_pointer);
+}
+
+
+bool ProfileEntryHookStub::SetFunctionEntryHook(FunctionEntryHook entry_hook) {
+  // We don't allow setting a new entry hook over one that's
+  // already active, as the hooks won't stack.
+  if (entry_hook != 0 && entry_hook_ != 0)
+    return false;
+
+  entry_hook_ = entry_hook;
+  return true;
+}
+
+
 } }  // namespace v8::internal