x86: mark the .rodata section also NX

The .rodata section shouldn't just be read-only,
but also non-executable. This is free since we've broken
up the 2MB page already anyway.

also update test_nx to check for this.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/test_nx.c

@@ -139,7 +139,6 @@ static int test_NX(void)
 	 * Until then, don't run them to avoid too many people getting scared
 	 * by the error message
 	 */
-#if 0
 
 #ifdef CONFIG_DEBUG_RODATA
 	/* Test 3: Check if the .rodata section is executable */
@@ -152,6 +151,7 @@ static int test_NX(void)
 	}
 #endif
 
+#if 0
 	/* Test 4: Check if the .data section of a module is executable */
 	if (test_address(&test_data)) {
 		printk(KERN_ERR "test_nx: .data section is executable\n");

arch/x86/mm/init_64.c

@@ -591,10 +591,17 @@ void mark_rodata_ro(void)
 	if (end <= start)
 		return;
 
-	set_memory_ro(start, (end - start) >> PAGE_SHIFT);
 
 	printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
 	       (end - start) >> 10);
+	set_memory_ro(start, (end - start) >> PAGE_SHIFT);
+
+	/*
+	 * The rodata section (but not the kernel text!) should also be
+	 * not-executable.
+	 */
+	start = ((unsigned long)__start_rodata + PAGE_SIZE - 1) & PAGE_MASK;
+	set_memory_nx(start, (end - start) >> PAGE_SHIFT);
 
 	rodata_test();