W^X enabled in Firefox port

CVSROOT:	/cvs
Module name:	ports
Changes by:	dcoppa@cvs.openbsd.org	2015/10/19 02:09:23

Modified files:
	www/mozilla-firefox: Makefile 
Added files:
	www/mozilla-firefox/patches: 
	                             patch-js_src_jit_ExecutableAllocator_cpp 

Log message:
Enable option to mark JIT pages as non-writable.

We're enabling this now so people can test and eventual regressions
can be catched and reported upstream.

There's a bug opened on Bugzilla@Mozilla:
https://bugzilla.mozilla.org/show_bug.cgi?id=1215479

OK landry@, sthen@
deraadt@ also agrees

Due to Apple's iOS requiring JIT pages to be non-writable, most of the upstream code was already in place. The patch itself is very simple, only altering the conditional check in the build to include OpenBSD as well:

$OpenBSD: patch-js_src_jit_ExecutableAllocator_cpp,v 1.1 2015/10/19 08:09:23 dcoppa Exp $

Mark JIT pages as non-writable

https://bugzilla.mozilla.org/show_bug.cgi?id=1215479

--- js/src/jit/ExecutableAllocator.cpp.orig	Tue Sep 29 23:44:56 2015
+++ js/src/jit/ExecutableAllocator.cpp	Fri Oct 16 17:02:15 2015
@@ -88,7 +88,7 @@ ExecutableAllocator::addSizeOfCode(JS::CodeSizes* size
     }
 }
 
-#if TARGET_OS_IPHONE
+#if defined(__OpenBSD__) || TARGET_OS_IPHONE
 bool ExecutableAllocator::nonWritableJitCode = true;
 #else
 bool ExecutableAllocator::nonWritableJitCode = false;

If you're a desktop user running snapshots, now's the time to help test. Initial testing shows a very minimal performance hit, but everyday users also need to give it a try and share their findings. If no issues are discovered, the patch will likely be merged upstream. Further discussion and status updates can be found in the Mozilla bug report and on the ports@ mailing list.