>Does execute protection work differently on PPC than on other >platforms?
Not in the CPU core, no. It's a bit in the page table entry just like on every other architecture. (Bit 61 "N" in the PTE is the "No execute" bit.) Of course, a multi-archtecture kernel (such as Linux) could apply different software policies and mechanisms to different architectures, since the code differs at least at some level.
