On Tue, Nov 5, 2019 at 11:55 AM Mark Rutland <mark.rutland@xxxxxxx> wrote: > On Mon, Nov 04, 2019 at 03:44:39PM -0800, Sami Tolvanen wrote: > > Sure, I'll add a better description in v5. In this case, the return > > address is modified in the kernel stack, which means the changes are > > ignored with SCS. > > Ok, that makes sense to me. I'd suggest something like: > > | The graph tracer hooks returns by modifying frame records on the > | (regular) stack, but with SCS the return address is taken from the > | shadow stack, and the value in the frame record has no effect. As we > | don't currently have a mechanism to determine the corresponding slot > | on the shadow stack (and to pass this through the ftrace > | infrastructure), for now let's disable the graph tracer when SCS is > | enabled. > > ... as I suspect with some rework of the trampoline and common ftrace > code we'd be able to correctly manipulate the shadow stack for this. > Similarly, if clang gained -fpatchable-funciton-etnry, we'd get that for > free. That sounds good to me. Thanks, Mark. Sami
