On Fri, Nov 17, 2023 at 01:12:46PM -0800, Deepak Gupta wrote: > On Tue, Nov 14, 2023 at 11:11:58PM +0000, Edgecombe, Rick P wrote: > > It seems like there will be a need for some generic method of checking > > if shadow stack is enabled. Maybe a more generic compiler > > intrinsic/builtin or glibc API (something unrelated to SSP)? > Exposing a new file under procfs would be useful? > Something like "/proc/sys/vm/user_shadow_stack_supported" > `map_shadow_stack` can return MAP_FAILED for other reasons. > I think `kselftests` are fine but I don't want people to pick up this > as test code and run with it in production :-) > So kernel providing a way to indicate whether it supports shadow stack > mappings in user mode via procfs would be useful and arch agnostic. I can see that might be useful for some higher level code that wants to tune the size and nothing else. I'd be tempted to do it through adding a tuneable for the maximum default shadow stack size (x86 currently uses 4G) just so it's *vaguely* useful rather than just a file. I question the utility of that but just a plain file doesn't feel quite idiomatic. In any case it feels like it's off topic for this series and should be done separately.
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