Comment by JdeBP

It says why it jumps over nops in the middle of a function. No explanation for jumping backwards at the end of a function.

And it replaces the nops with int3. Not another jump. This code keeps stacking d4.

Putting instructions that halt execution in unreachable parts of the code would make sense, but this is just a jump with a fixed offset, which may technically still be exploitable.

If trap instructions are not possible, I would at least try to make it an unconditional jump to create an infinite loop.