Behind the Scenes with iOS Security

4. Prevent writing into the executable JIT mapping.
result = mprotect(jitBase, jitSize, VM_PROT_READ | VM_PROT_EXECUTE);
RELEASE_ASSERT(!result);
// 5. Prevent execution in the writable JIT mapping.
result = mprotect((void*)writableAddr, jitSize, VM_PROT_READ | VM_PROT_WRITE);
RELEASE_ASSERT(!result);
// 6. Zero out writableAddr to avoid leaking the address of the writable mapping.
memset_s(&writableAddr, sizeof(writableAddr), 0, sizeof(writableAddr));
jitWriteFunction =
reinterpret_cast(writeThunk.code().executableAddress());
}