Zachary Amsden wrote:You need to get a #GP or #NP on the faulting iret. Several ways to do that -I do that much simpler - I provoke a SIGSEGV and in a signal handler
I put the wrong value to scp->cs or scp->ss, and that makes iret to fault.
iret faults, but doesn't pop the user return frame.But does it push the kernel frame after it or not?
If not - I don't understand how we go to a fixup.
If yes - I don't understand how the user's frame gets
accessed later, as it is above the kernel's frame.
I think regs->esp + THREAD_SIZE*2 is already very permissive,safe limit is regs->esp + THREAD_SIZE*2... Well, may just I not do that please? :)It helps track down any bugs that could leak through otherwise and corrupt random memory.
For what, btw? There are no such a things for __KERNEL_DS or anything, so
I just don't see the necessity.
and I'd like to avoid messing with granularity. So unless you
really insist, I'll better not do that. :)