4 ms·

> Meet the above test suite requirement if Just in Time (JIT) compilation is unavailable (e.g., if Lockdown Mode is enabled by the user) Interesting, I wasn't

> Meet the above test suite requirement if Just in Time (JIT) compilation is unavailable (e.g., if Lockdown Mode is enabled by the user) Interesting, I wasn't aware that Lockdown Mode disabled JIT. Does it do that system-wide, or only for third party apps?

nnx 2y ago
This disables JIT for JSC (JavaScriptCore) system-wide. Third party apps never had been able to JIT on iOS, no permission to write executable pages.
- vmfunction 2y ago
  Isn't it possible to used JIT for JSC in WebView?
  - johncolanduoni 2y ago
    WKWebView and SafariViewController do, but they run the browser engine and JIT in another process so that the app still doesn’t have the ability to execute unsigned pages.
    - vmfunction 2y ago
      Interesting! How are unsigned pages determined this case?
liamwire 2y ago
As far as I’m aware, JIT isn’t available to third-party apps on iOS and iPadOS.
Scaevolus 2y ago
Yes. It makes JS run at ~30% speed, a worthwhile tradeoff given how often JIT bugs are used in exploit chains. https://daringfireball.net/2024/06/apple_disables_webkits_jit_in_lockdown_mode https://daringfireball.net/2024/06/apple_disables_webkits_ji...
withinboredom 2y ago
System wide. This is documented