Hi,
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.
safe limit is regs->esp + THREAD_SIZE*2... Well, may just I not do
that please? :)
For what, btw? There are no such a things for __KERNEL_DS or anything, so
I just don't see the necessity.
It helps track down any bugs that could leak through otherwise and
corrupt random memory.
I think regs->esp + THREAD_SIZE*2 is already very permissive,
and I'd like to avoid messing with granularity. So unless you
really insist, I'll better not do that. :)
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