Change the pnacl shim from doing real shimming to just intercepting

src/untrusted/pnacl_irt_shim/shim_entry.c

Index: src/untrusted/pnacl_irt_shim/shim_entry.c
===================================================================
--- src/untrusted/pnacl_irt_shim/shim_entry.c	(revision 9574)
+++ src/untrusted/pnacl_irt_shim/shim_entry.c	(working copy)
@@ -1,16 +1,45 @@
 /*
- * Copyright (c) 2011 The Native Client Authors. All rights reserved.
+ * Copyright 2011 The Native Client 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 <stddef.h>
 #include "native_client/src/include/elf32.h"
 #include "native_client/src/include/elf_auxv.h"
 #include "native_client/src/include/nacl_macros.h"
-#include "native_client/src/untrusted/pnacl_irt_shim/shim_ppapi.h"
+#include "native_client/src/untrusted/irt/irt.h"
+#include "native_client/src/untrusted/irt/irt_shim.h"
 #include "native_client/src/untrusted/nacl/nacl_startup.h"
 
+/*
+ * For more information about this hack cf.
+ * src/untrusted/irt/irt_ppapi.c
+ */
 
+static TYPE_nacl_irt_query real_irt_interface;
+
+/* cf. src/untrusted/irt/irt.h  NACL_IRT_PPAPIHOOK_(SHIMMED_)v0_1 */
+static const char prefix_search[] = "nacl-irt-ppapihook";
+static const char prefix_replace[] = "nacl-irt-ppapihook-shimmed";
+
+/* Do not make assumptions about strcmp being available. */
+static int my_strcmp(const char* s1, const char* s2) {
+  while (*s1 != '\0' && *s2 != '\0' && *s1 == *s2) {
+    s1++;
+    s2++;
+  }
+  return *s1 - *s2;
+}
+
+static size_t pnacl_irt_interface_interceptor(const char *interface_ident,
+                                              void *table, size_t tablesize) {
+  if (0 == my_strcmp(interface_ident, NACL_IRT_PPAPIHOOK_v0_1)) {
+    return real_irt_interface(NACL_IRT_PPAPIHOOK_SHIMMED_v0_1, table, tablesize);
+  }
+  return real_irt_interface(ident, table, tablesize);
+}
+
 /*
  * This is the true entry point for untrusted code.
  * See nacl_startup.h for the layout at the argument pointer.
@@ -30,13 +59,13 @@
     /*
      * Save the real irt interface.
      */
-    __pnacl_real_irt_interface = (TYPE_nacl_irt_query) entry->a_un.a_val;
+    real_irt_interface = (TYPE_nacl_irt_query) entry->a_un.a_val;
 
     /*
      * Overwrite the auxv slot with the pnacl IRT shim query function.
      */
     entry->a_type = AT_SYSINFO;
-    entry->a_un.a_val = (uintptr_t) __pnacl_irt_interface_wrapper;
+    entry->a_un.a_val = (uintptr_t) pnacl_irt_interface_interceptor;
   }
 
   /* If entry is NULL still allow startup to continue.  It may be the case