On Tue, 2023-01-24 at 15:08 -0800, Kees Cook wrote: > > GDB support for shadow stack is queued up for whenever the kernel > > interface settles. I believe it just uses ptrace, and not this > > proc. > > But yea ptrace poke will still need to use FOLL_FORCE and be able > > to > > write through shadow stacks. > > I'd prefer to avoid adding more FOLL_FORCE if we can. If gdb can do > stack manipulations through a ptrace interface then let's leave off > FOLL_FORCE. Ptrace and /proc/self/mem both use FOLL_FORCE. I think ptrace will always need it or something like it for debugging. To jog your memory, this series doesn't change what uses FOLL_FORCE. It just sets the shadow stack rules to be the same as read-only memory. So even though shadow stack memory is sort of writable, it's a bit more locked down and FOLL_FORCE is required to write to it with GUP. If we just remove FOLL_FORCE from /proc/self/mem, something will probably break right? How do we do this? Some sort of opt-in?
