Show more different NaCl loading errors.

ppapi/native_client/src/trusted/plugin/service_runtime.cc

Index: ppapi/native_client/src/trusted/plugin/service_runtime.cc
===================================================================
--- ppapi/native_client/src/trusted/plugin/service_runtime.cc	(revision 211556)
+++ ppapi/native_client/src/trusted/plugin/service_runtime.cc	(working copy)
@@ -727,17 +727,23 @@
         "ServiceRuntime: failed to create sel_ldr launcher");
     return false;
   }
+  nacl::string error_message;
   bool started = tmp_subprocess->Start(plugin_->pp_instance(),
                                        params.url.c_str(),
                                        params.uses_irt,
                                        params.uses_ppapi,
                                        params.enable_dev_interfaces,
                                        params.enable_dyncode_syscalls,
-                                       params.enable_exception_handling);
+                                       params.enable_exception_handling,
+                                       &error_message);
   if (!started) {
     NaClLog(LOG_ERROR, "ServiceRuntime::Start (start failed)\n");
-    params.error_info->SetReport(ERROR_SEL_LDR_LAUNCH,
-                                 "ServiceRuntime: failed to start");
+    if (error_message.empty()) {
+      params.error_info->SetReport(ERROR_SEL_LDR_LAUNCH,
+                                   "ServiceRuntime: failed to start");
+    } else {
+      params.error_info->SetReport(ERROR_SEL_LDR_LAUNCH, error_message);

[Mark Seaborn, 2013/07/16 02:02:53]

This error gets reported to untrusted Javascript via lastError, doesn't it?  I'm
not sure that is a good idea.  It will expose platform-specific errors like
messages about DuplicateHandle().  There's a risk that error messages are
unintentionally changed in the future to leak sensitive information.

What error messages are exposed to Javascript at the moment?  Maybe we could
reduce the set, or at least not increase it?

Nick has worked on this error-handling code before.  Maybe he can comment?

[halyavin, 2013/07/16 08:04:35]

Looks like you are right.
Do you want to have different errors printed to the javascript console and set
to lastError?

[Mark Seaborn, 2013/07/17 05:29:58]

Yes, I think so, to avoid accidentally exposing sensitive information, and to
avoid apps depending on specific messages.

You'd only need to hide the new errors you're adding from Javascript.

[halyavin, 2013/07/17 13:12:16]

Done.

+    }
     return false;
   }