t, w_ = a+b, kern_mem[address] u, x_ = t+c, w_&0x100 v, y_ = u+d, user_mem[x_] if v: # fault w, x, y = w_, x_, y_ # we never get here F

t, w_ = a+b, kern_mem[address] u, x_ = t+c, w_&0x100 v, y_ = u+d, user_mem[x_] if v: # fault w, x, y = w_, x_, y_ # we never get here Form the author's example, it seems like the processor is able to read the kernel memory privately (`w_`) and crashes if the code attempts to commit `w_` to `w`. It would be interesting to know how the processor does that.