I think iOS makes use of NX bits such that for your vanilla app, the executable pages aren't writable and writable pages aren't executable. Historically, this r

I think iOS makes use of NX bits such that for your vanilla app, the executable pages aren't writable and writable pages aren't executable. Historically, this resulted in WebViews not having JS JIT which severely impacted performance. Apple later came out with WKWebView which underneath the covers runs the browser engine as a standalone process which is able to write executable memory and thus able to JIT JS.