Update iOS JIT hack

[sbingner]

The current hack being used to get read/write/execute memory on iOS leaves the process in a very bad state where it can never exit. I fixed the hack for another project and somebody pointed out that I should let you guys know about it. The attached hack will get the same RWX memory state but without leaving the process in a bad state that does not allow it to be killed or exit.

[rweichler]

🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥

[hrydgard]

Can't say I completely understand what's going on here, but if it fixes it, it fixes it...

[sbingner]

Can't say I completely understand what's going on here, but if it fixes it, it fixes it...
For posterity and edification:

The problem with the original hack was that it says it expects to be debugged but nothing ever debugs it. I fixed this by having something actually debug it.

1. It spawns a child, and waits for that child to exit
2. That child connects to its parent and debugs it.
3. Once the child is attached to the parent, it just detaches and exits. This permanently marks the parent as having been debugged.
4. The parent can then continue normal execution and pages that are not CS valid or are later created not valid do not cause problems because the kernel knows that a debugger may have modified code in the parent.

[hrydgard]

Ah, that explains it! Very cool!

[Halo-Michael]

Thanks!