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

src/trusted/service_runtime/sel_main_chrome.c

Index: src/trusted/service_runtime/sel_main_chrome.c
diff --git a/src/trusted/service_runtime/sel_main_chrome.c b/src/trusted/service_runtime/sel_main_chrome.c
index 35dfa02a120fd8a4400c750dbf7c775d798a5766..e7dbfe1c49b9c7c993d59948c2f9e2e7ea14d73e 100644
--- a/src/trusted/service_runtime/sel_main_chrome.c
+++ b/src/trusted/service_runtime/sel_main_chrome.c
@@ -280,8 +280,22 @@ void NaClChromeMainStart(struct NaClChromeMainArgs *args) {
     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, to provide better
+   * diagnostics when the linker did not create a segment gap!

[Mark Seaborn, 2012/06/28 22:50:55]

ditto: "when the nexe does not follow NaCl's stable ABI"

[jvoung - send to chromium..., 2012/06/28 23:02:50]

Done.

+   */
+  if (NULL != nap->text_shm) {
+    NaClLoadIrt(nap, args->irt_fd);
+  } else {
+    NaClLog(
+        LOG_WARNING,
+        "Main executable has no segment gap; skipping loading IRT library.\n"

[Mark Seaborn, 2012/06/28 22:50:55]

ditto about multi-line

[jvoung - send to chromium..., 2012/06/28 23:02:50]

Done.

+        "This is expected for PNaCl's translator nexes.\n");
+  }
 
   NaClEnvCleanserCtor(&env_cleanser, 1);
   if (!NaClEnvCleanserInit(&env_cleanser, envp, NULL)) {