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

include/v8.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3161 matching lines @@
   static void SetEntropySource(EntropySource source);
 
   /**
    * Allows the host application to provide a callback that allows v8 to
    * cooperate with a profiler that rewrites return addresses on stack.
    */
   static void SetReturnAddressLocationResolver(
       ReturnAddressLocationResolver return_address_resolver);
 
   /**
+   * Allows the host application to provide the address of a function that's
+   * invoked on entry to every V8-generated function.
+   * Note that the entry_hook function is invoked at the very start of
+   * each generated function, before a stack frame is constructed, volatile
+   * registers saved etc. This function therefore must preserve all registers,
+   * and will likely need to be written in assembly.
+   */
+  static void SetFunctionEntryHook(uintptr_t entry_hook);

[danno, 2012/06/27 23:01:54]

I am not sure exactly what the right thing to do is, but it seems a bit fragile
that the call silently fails on x64 and ARM.

[Sigurður Ásgeirsson, 2012/06/28 09:41:41]

Good point. Another thing that occurred to me is that there's no way to "stack"
this API, e.g. it doesn't make sense to have multiple profilers active at the
same time.
How about having this function return bool, return true on success, and fail it
on unsupported platforms as well as on setting any transition except to and from
a NULL hook?

+
+  /**
    * Adjusts the amount of registered external memory.  Used to give
    * V8 an indication of the amount of externally allocated memory
    * that is kept alive by JavaScript objects.  V8 uses this to decide
    * when to perform global garbage collections.  Registering
    * externally allocated memory will trigger global garbage
    * collections more often than otherwise in an attempt to garbage
    * collect the JavaScript objects keeping the externally allocated
    * memory alive.
    *
    * \param change_in_bytes the change in externally allocated memory
@@ skipping 1304 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_