Enable check for DEP / NX page protection

src/trusted/platform_qualify/win/nacl_dep_qualify.c

Index: src/trusted/platform_qualify/win/nacl_dep_qualify.c
===================================================================
--- src/trusted/platform_qualify/win/nacl_dep_qualify.c	(revision 3470)
+++ src/trusted/platform_qualify/win/nacl_dep_qualify.c	(working copy)
@@ -15,22 +15,56 @@
 #include <stdlib.h>
 
 #include "native_client/src/trusted/platform_qualify/nacl_dep_qualify.h"
+#include "native_client/src/trusted/service_runtime/nacl_signal.h"
 
+static int g_SigFound;
+
+static enum NaClSignalResult signal_catch(int in_untrusted_code,
+                                          int signal,
+                                          void *ctx) {
+  UNREFERENCED_PARAMETER(ctx);
+  /* Should be a trusted segfault */
+  if (!in_untrusted_code && 11 == signal) {
+    g_SigFound = signal;
+    return NACL_SIGNAL_SKIP;
+  }
+  return NACL_SIGNAL_SEARCH; /* some other signal we weren't expecting */
+}
+
+static int setup_signals() {
+  return NaClSignalHandlerAdd(signal_catch);
+}
+
+static void restore_signals(int handlerId) {
+  if (0 == NaClSignalHandlerRemove(handlerId)) {
+    /* What to do if the remove failed? */
+    fprintf(stderr, "Failed to unload handler.\n");
+  }
+}
+
 /*
  * Returns 1 if Data Execution Prevention is present and working.
  */
 int NaClAttemptToExecuteData() {
   int result;
+  int handlerId;
   char *thunk_buffer = malloc(64);
   nacl_void_thunk thunk = NaClGenerateThunk(thunk_buffer, 64);
 
+  handlerId = setup_signals();
+  g_SigFound = 0;
   __try {
     thunk();
+  } __except (EXCEPTION_EXECUTE_HANDLER) {
+  }
+
+  /* Should be a segfault */
+  if (11 == g_SigFound) {
+    result = 1;
+  } else {
     result = 0;
-  } __except (GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION ?
-              EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH) {
-    result = 1;
   }
 
+  restore_signals(handlerId);
   return result;
 }