Allow sel_ldr to continue without the IRT, when nexe doesn't have segment gap

src/trusted/service_runtime/sel_main_chrome.c

 /*
  * Copyright (c) 2012 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 "native_client/src/trusted/service_runtime/sel_main_chrome.h"
 
 #include "native_client/src/include/portability.h"
 #include "native_client/src/include/portability_io.h"
@@ skipping 262 matching lines @@
     }
   }
 
   /*
    * error reporting done; can quit now if there was an error earlier.
    */
   if (LOAD_OK != errcode) {
     goto done;
   }
 
-  /* Load the integrated runtime (IRT) library. */
-  NaClLoadIrt(nap, args->irt_fd);
+  /*
+   * Load the integrated runtime (IRT) library.
+   * We check if there is a segment gap before trying to load the IRT.  This
+   * is to support IRT-less / segment-gap-free PNaCl translator nexes.
+   * TODO(mseaborn): Plumb through a flag from Chrome in such cases,
+   * instead of looking for the absence of a segment gap, when the nexe does
+   * not follow NaCl's stable ABI.
+   */
+  if (NULL != nap->text_shm) {
+    NaClLoadIrt(nap, args->irt_fd);
+  } else {
+    NaClLog(
+        LOG_WARNING,
+        "Main executable has no segment gap; skipping loading IRT library. "
+        "This is expected for PNaCl's translator nexes.\n");
+  }
 
   NaClEnvCleanserCtor(&env_cleanser, 1);
   if (!NaClEnvCleanserInit(&env_cleanser, envp, NULL)) {
     NaClLog(LOG_FATAL, "Failed to initialise env cleanser\n");
   }
 
   if (!NaClAppLaunchServiceThreads(nap)) {
     fprintf(stderr, "Launch service threads failed\n");
     goto done;
   }
@@ skipping 37 matching lines @@
   if (LOAD_OK != errcode) {
     NaClBlockIfCommandChannelExists(nap);
   }
 
  done_ctor:
 
   NaClAllModulesFini();
 
   NaClExit(ret_code);
 }