Dynamic loading: Fill pages with halts only when they are needed

src/native_client/tests/dynamic_code_loading/nacl.scons

Index: src/native_client/tests/dynamic_code_loading/nacl.scons
diff --git a/src/native_client/tests/dynamic_code_loading/nacl.scons b/src/native_client/tests/dynamic_code_loading/nacl.scons
index f5f3652a86010ff8da5924e72c2e9f74276af5e4..b7d77c3117aae025c48b0d54e81c586428fddd40 100644
--- a/src/native_client/tests/dynamic_code_loading/nacl.scons
+++ b/src/native_client/tests/dynamic_code_loading/nacl.scons
@@ -84,6 +84,10 @@ prog_env.ComponentProgram('debug_mode_test.nexe',
                            template_obj],
                           EXTRA_LIBS=['nacl_dyncode'])
 
+prog_env.ComponentProgram('dyncode_demand_alloc_test.nexe',
+                          ['dyncode_demand_alloc_test.c'],
+                          EXTRA_LIBS=['nacl_dyncode'])
+
 tests = [
     prog_env.CommandSelLdrTestNacl(
         'dynamic_load_test.out',
@@ -111,6 +115,14 @@ tests = [
         sel_ldr_flags=["-c"],
         command=[prog_env.File('debug_mode_test.nexe')],
         ),
+    # This tests, from untrusted code, that dyncode pages are
+    # inaccessible before they are allocated.
+    prog_env.CommandSelLdrTestNacl(
+        'dyncode_demand_alloc_test.out',
+        command=[prog_env.File('dyncode_demand_alloc_test.nexe')],
+        exit_status='untrusted_segfault',
+        stdout_golden=prog_env.File('dyncode_demand_alloc_test.stdout'),
+        ),
   ]
 if not prog_env.Bit('target_arm'):
   tests.append(prog_env.CommandSelLdrTestNacl(