Re: luajit and iOS
- From: Adam Strzelecki <ono@xxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Fri, 7 Sep 2012 00:08:10 +0200
This was already discussed some time ago on Lua ML (once there was no LuaJIT
ML).
Have a look here:
http://lua-users.org/lists/lua-l/2011-04/msg01035.html
There is no physical/hardware limitation of JIT on iOS. Calling mprotect on iOS
5 to set execute flag requires the app to have special entitlements (speaking
only about non jailbroken device). The only app on iOS that has this
entitlement is Safari because it needs that for Nitro JS engine.
So in theory your app could have such entitlement so iOS kernel will let you
call mprotect to use JIT, but Apple won't issue such entitlement to you, even
they if did, mprotect can be called only once and only for specific VM pages,
which may be no-go for LuaJIT.
There's pretty decent book about such internals by Charlie Miller:
http://www.amazon.com/iOS-Hackers-Handbook-Charlie-Miller/dp/1118204123
Note that first iOS version that introduced support for mprotect was iOS 4, and
due to the bug in its XNU kernel it was possible to set execute flag even
having absolutely no entitlements to do so ;) Now in iOS 5 it is fixed and
works as described above.
Cheers,
--
Adam Strzelecki
Other related posts:
